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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
| 10 BASE-T |
| The Institute of Electrical and Electronic Engineers (IEEE) 802.3 specification for ethernet over thin coaxial cable. |
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| 2B1Q |
| 2 binary, one quarternary. A one-dimensional modulation for transmitting 2 bits per symbol. 2B1Q is a 4-level PAM(pulse amplitude modulation) system used for HDSL, S-HDSL, and ISDN BRI. |
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| Absolute Maximum Ratings |
| Specifications that, if exceeded, could cause permanent damage to the converter. There are not continuous ratings, and proper operation is not implied. |
| Absolute Permeability |
| The permeability of a magnetic material expressed in actual physical units, not relative to permeability of free space. The permeability of magnetic materials is rarely expressed in terms of absolute permeability. The usual mode is in terms of relative permeability. |
| AC Filter |
| A filter circuit that removes unwanted frequencies (harmonics) from a mostly AC current. This would include some EMI filters. |
| AC Flux Density (Gauss) |
| Number of flux lines per unit of cross-sectional area generated by an alternating magnetic field. |
| Access Method |
| The method by which networked stations determine when they can transmit data on a shared transmission medium. Also, the software within an SNA processor that controls the flow of information through a network. |
| Access Provider |
| Organization providing and maintianing network services for subscribers. |
| Access Rate |
| The transmission speed, in bits per second, of the physical access circuit between the end user and the network. |
| Active High |
| Power switch enable input voltage must exceed the deviceÕs defined threshold voltage for the device to turn on (typically 1.5V). Conversely, enable input voltage must fall below the threshold voltage to turn the device off. |
| Active Low |
| Power switch enable input voltage must fall below the deviceÕs defined threshold voltage for the device to turn on (typically 1.5V). Conversely, enable input voltage must exceed the threshold voltage to turn the device off. |
| ADSL |
| A new method of transmitting at speeds up to 7 Mbps in one direction over a single copper telephone line, with up to 640 kbps in the other direction. |
| Aging |
| Operating a converter under controlled conditions for a predetermined time in order to screen out failures. Also see Burn-in. |
| Air Core Inductance |
| The inductance that would be measured if the core had unity permeability and the flux distribution remained unaltered. (A measure of the inductance of a coil without a core). |
| Air Gap |
| A non-magnetic discontinuity in a ferro-magnetic circuit. For example, the space between the poles of a magnet, if filled with brass, wood, or any other non-magnetic material, is nevertheless called an air gap. Air gaps are often introduced into soft ferrite cores to prevent saturation at high DC bias currents or to simply hold a tight inductance tolerance. |
| AL Value (nH/N2) |
| The inductance rating of a core in nanoHenries per turn squared (nH/N2) based on a peak flux density of 10 gauss (1 milliTesla) at a frequency of 10 kHz. An AL value of 40 would produce 400µH of inductance for 100 turns and 40mH for 1000 turns. |
| Ambient Temperature(CoEv) |
| The temperature of still air immediately surrounding a component or circuit. A typical method to measure ambient temperature is to record the temperature that is approximately _ inch from the body of the component or circuit. |
| Ambient Temperature(Raychem) |
| The temperature of still air immediately surrounding a component or circuit. A typical method to measure ambient temperature is to record the temperature that is approximately 1/2 inch from the body of the component or circuit. |
| Amorphous |
| Refers to magnetic materials that are metallurgically non-crystalline in nature. |
| Ampere Turns (NI) |
| The product of current (I) flowing in the winding times the number of turns (N). |
| Ampere-Turns Per Meter (At/m or A/m) |
| The MKS unit of magnetizing force, H, as shown by AmpereÕs Law. |
| Amplitude Permeability (µa) |
| The quotient of the peak value of flux density and peak value of applied field strength at a stated amplitude of either, with no static field present. |
| Anisotropic |
| A material whose electrical properties vary with different polarization of a traveling wave. |
| Anneal |
| A high-temperature conditioning of magnetic material to relieve stresses introduced when the material was formed. |
| ANSI T1.403 |
| The performance-monitoring, data-link, and network interface requirements for ESF CSUs as defined by the Exchange Carriers Standards Association. T1.403 specifies automatic performance reports transmitted to the network once per second via the data link. (In an E1 environment, Performance Monitor is the equivalent of T1.403). |
| ANSI T1.413 |
| The interface standard for DMT ADSL. |
| ASIC |
| application specific integrated circuit |
| ASP |
| Application service provider |
| Assymetrical Transmission |
| Transmission which sends data at different rates in each direction, faster downstream than upstream. |
| ATM |
| The key emerging technology that uses fixed-length packets or cells to switch voice, data and video traffic over the local- and wide-area network. |
| Attenuation(CoEv) |
| The relative decrease in amplitude of a given parameter. Attenuation measurements are common for voltage, current, and power. It is usually expressed in decibels (dB). For a power ratio, one dB = 10Log10(P1/P2). For a current ratio, one dB = 20Log10(I1/I2). For a voltage ratio, one dB = 10Log10(V1/V2). |
| Attenuation(Raychem) |
| The relative decrease in amplitude of a given parameter. Attenuation measurements are common for voltage, current and power. It is usually expressed in units of decibels (dB). For a power ratio, one dB=10Log(P1/P2). A dB is equal to 20Log(I1/I2) for current and 20Log(V1/V2) for voltage ratios. |
| AWG (American Wire Gauge) |
| A gauging system used to size wire. Every increase of 3 wire gauges is a 50% reduction in cross sectional area of the wire. |
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| B Channel |
| In ISDN, a full duplex, 64 kbps channel sending data. |
| B-H Curve |
| Curve to show charactaristics of a magnetic material, in terms of magnetizing force (H) and resulting flux density. |
| Backbone Network |
| The main artery or link for a private or public network. Typically the backbone carries the lion's share of traffic (data, voice, video or some combination), is capable of carrying significant bandwidth and it is the network to which small/remote networks/links are attached. |
| Balun Filter |
| Input line filter often used on DC-DC converters that include a differential wound transformer. Balun filters present a low impedance to differential mode signals and a high impedance ot common mode signals. |
| Band Pass |
| The frequency range over which an inductor or capacitor exhibits a low impedance. |
| Band Stop |
| The frequency range over which an inductor or capacitor exhibits a high impedance. |
| Bandwidth |
| A term now used to describe the capacity or amount of traffic (data, voice or video) a certain communications line is capable of accommodating. |
| Base Plate |
| Substrate to which circuit components are mounted or, a metal plate to which the converter is attached. Normally used to draw heat away from critical circuit components. Also see Heat Sink. |
| Base Plate Temperature |
| See Case Temperature |
| Base Resistance |
| The resistance of a PolySwitch device under specified conditions (e.g., 20¡C), before connection into a circuit. Devices of a particular type will be delivered with a range of resistances; therefore, a minimum value, Rmin, and/or a maximum value, Rmax, are often given. |
| Synonyms: Initial Resistance,Resistance,Rmin,or Rmax |
| Baseband |
| Transmission scheme in which the entire bandwidth, or data-carrying capacity, of a medium (such as coaxial cable) is used to carry a single digital pulse, or a signal, between multiple users. Because digital signals are not modulated, only one kind of data can be transmitted at a time. Contrast with broadband. |
| Basic Encoding Rate (BER) |
| Rule of encoding data units described in ANS.1. |
| Basic Rate Interface (BRI) |
| Reference ISDN. |
| Battery Backup |
| Subsystem for electronic equipment that provides power in the event of input power loss. Battery backed systems are a common application are for DC-DC converters. |
| BH Loop |
| A hysteresis loop showing magnetic characteristics of a magnetic material as an alternating current is applied. |
| BHMAX (Maximum Energy Product) |
| Indicates the maximum energy that a magnetic material can supply to an external magnetic circuit when operating at the Bd, Hd point on its demagnetization curve, measured in megaGauss-Oersteds (MGOe) or kiloJoules per cubic meter (kJ/m3). |
| Bifilar Winding |
| Two strands of magnet wire wound side-by-side. |
| Binned |
| Binned refers to resistance-matched devices, which are supplied such that all parts in one particular package (or reel) are within 0.5 ohms of each other (1.0 ohms for TR250-080T devices). Individual matched packages are supplied from the full resistance range of the specified device. The benefit is that resistance-matched devices reduce the tip-ring resistance differential, reducing the possibility of line imbalance. Sorted devices are those that are supplied with resistance values that are within specified segments of the device's full range of resistance, giving greater design flexibility. |
| Synonyms: Sorted |
| Bit Error Rate (BER) |
| The ratio of received bits that are in error. |
| Bits Per Second (bps) |
| The number of bits passing a point every second. The transmission rate for digital information. |
| BLEC |
| building local exchange carrier |
| Bobbin Core(CoEv) |
| A core with the shape of a bobbin or spool which contains flanges. Bobbin cores are available with and without leads and in the axial and radial form. |
| Bobbin Core(Raychem) |
| A core with the shape of a bobbin or spool which contains flanges |
| Boost Regulator |
| A basic DC-DC switching converter topology that takes an unregulated input voltage and produces a higher regulated output voltage. The higher output voltage is achieved by storing energy in an input inductor and then transferring the energy to the output by turning a shunt switch (transistor) on and off at a fast rate. |
| Breakdown Voltage |
| Maximum AC or DC voltage that can be applied from the input to output (or chassis) of a converter without causing damage. |
| Breakover Current |
| Instantaneous current flowing at the breakover voltage, VBO. |
| Breakover Voltage |
| Maximum voltage across a SiBar device at breakdown measured under a specified voltage rate of rise and current rate of rise. |
| Synonyms: System Damage Voltage |
| Bridge Converter |
| Switching converter topology that employs four switching elements (full bridge) or two switching elements (half-bridge). This topology is more often used in off-line supplies rather than DC-DC converters. Bridge converters provide high output power and low ripple, but are significantly more complex than other types of converter topologies and thus are more expensive and prone to failure. Also see Boost Regulator, Buck Regulator, Flyback Converter, Foward Converter, Push-Pull Converter and Resonant Converter. |
| Bridge/Router |
| A device that can provide the function of a bridge, router or both concurrently. Bridge/router can route one or more protocols, such as TCP/IP and/or XNS, and bridge all other traffic. |
| Broadband |
| Data transmission at a high rate, generally greater than T1 speeds (1.5 Mbps). This allows the transmission of voice, data and video signals over a single medium. |
| BSP |
| broadband service provider |
| Buck Boost Converter |
| See Flyback Converter |
| Buck Derived Converter |
| See forward converter |
| Buck Regulator |
| A basic DC-DC switching converter topology that takes an unregulated input voltage and produces a lower regulated output voltage. The lower output voltage is achieved by chopping the input voltage with a series connected switch (transistor) which applies pulses to an averaging inductor and capacitor. |
| Buck Regulator (DC-DC) |
| A basic DC-DC switching converter topology that takes an unregulated input voltage and produces a lower regulated output voltage. This output voltage is achieved by chopping the input voltage with a series connected switch (transistor) which applies pulses to an averaging inductor and capacitor. |
| Burn In |
| Operation of newly manufctured converters for some period of time prior to shipment. The intent is to stabilize the converter and eliminate infant mortality by aging the device. The time period and conditions (input power cycling, load switching, temperature, etc.) varies from vendor to vendor. However, the less stringent the conditions, the less likely it is that potential problems will be caught by the vendor. |
| Bus |
| Primary conductor path (wires, cables, etc.) used for routing power to various components within a (sub)system. |
| Bus-powered |
| Class of devices that derive their power from the main Hub. Examples include USB hubs, keyboards, mice, internet cameras. |
| Butt Gap |
| A gap, mostly found in E cores, that is obtained by equally spacing all mating surfaces of the core, usually by plastic shims or some other non-magnetic material. This is an alternative to center post gapping, where only the center leg of a core is gapped. To achieve the same gap electrically a center leg gap must be twice as much as a butt gap. |
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| Cable Modem |
| Modem designed for use on TV coaxial cable circuit. |
| Campus Area Network |
| A network which encompasses interconnectivity between floors of a building and/or buildings in a confined geographic area such as a campus or industrial park. Such networks would not require public rights-of-way and operate over fairly short distances. |
| Canadian Standards Association (CSA) |
| Independent organization that establishes and tests safety standards for electronic components and systems for the Canadian marketplace. |
| CAP |
| Carrierless Amplitude Phase Modulation. A two-dimensional line code used in ADSL. |
| Capacitor |
| A device that stores electrostatic energy in a manner similar to the way an inductor stores electromagnetic energy. Often used for filtering or DC blocking. The unit of capacitance is the Farad. |
| CAPs |
| Competative Access Provider or Competative Local Exchange Carrier. Alternative provider to Local Exchange Carrier. |
| Carbonyl Iron |
| A relatively expensive iron powder used in low permeability, high frequency powdered iron cores. |
| Case Temperature |
| Temperature of the case when the converter and surrounding system are operating normally. Often used as a specification for DC-DC converters with extended temperature ranges. Case temperature is at times referred to as a Base Plate Temperature. |
| CCITT |
| Consultative Committee for International Telegraph and Telephone- The former name of an international organization that develops communications standards such as Recommendation X.25. Now called ITU-T. |
| CDMA |
| code division multiple access |
| Ceramic Cores |
| One of the common materials used for inductor cores. Its main purpose is to provide a form for the coil. In some designs it also provides the structure to hold the terminals in place. Ceramic has a very low thermal coefficient of expansion, which allows for relatively high inductance stability over the operating temperature ranges. Ceramic has no magnetic properties. Thus, there is no increase in permeability due to the core material. Ceramic core inductors are often referred to as Òair coreÓ inductors. Ceramic core inductors are most often used in high frequency applications where low inductance values, very low core losses, and high Q values are required. |
| CFM |
| Cubic feet per minute, which is a measure of the volume of air flowing in a system. |
| Channel |
| A communication path. Multiple channels can be multiplexed over a single cable in certain environments. The term is also used to describe the specific path between large computers and attached peripherals. |
| Choke |
| An inductor which is intended to filter, or ÒchokeÓ, out unwanted signals. |
| Churn |
| A term used to describe turnover in subscribers of various media such as magazines, newspapers, cable, and videotex services. Churn is an important measures of a medium's success in holding on to customers after they have been signed up as subscribers. |
| Circuit Switching |
| Switching systems in which a dedicated physical circuit path must exist between sender and receiver for the duration of the "call". Used heavily in the phone company network, circuit switching often is contrasted with contention and token passing as a channel-access method, and with message switching and packet switching as a switching technique. |
| Circuit-Switched Network |
| Network that establishes a physical circuit temporarily, until it receives a disconnect signal. |
| Circular Mils (cm) |
| The cross sectional area of a circular conductor calculated as a square conductor (cm is the diameter squared). This is often used in power applications for current handling capability vs. temperature rise. |
| CLEC |
| A distributed system model of computing that brings computing power to the desktop, where users("clients") access resources from servers. |
| Client/Server |
| A distributed system model of computing that brings computing power to the desktop, where users("clients") access resources from servers. |
| Clock |
| Timing pulses used within a system or circuit to synchronize the operation of components. In a DC-DC converter, these pulses are used to synchronize operation of the PWM chips. |
| Close Magnetic Path |
| Magnetic core shapes designed to contain all of the magnetic flux generated from an excited winding(s). Inductors made with these core types are considered to be shielded inductors. Shielding, however, is a matter of degree. Common core shapes that are considered to have closed magnetic paths are toroids, E-cores, and most pot cores. Shielded bobbins also offer a high degree of shielding but most have an air gap to some degree. Common core shapes that are considered to have open magnetic flux paths are rod cores and unshielded bobbin cores. |
| Closed Magnetic Path |
| Magnetic core shapes designed to contain all of the magnetic flux generated from an excited winding(s). Inductors made with these core types are considered to be shielded inductors, although shielding is a matter of degree. Common core shapes that are considered to have closed magnetic paths are toroids, E-cores, and most pot cores. These core shapes do, however, contain minute air gaps that are unavoidable in manufacturing. Some common core shapes considered to have open magnetic flux paths are rod cores and unshielded bobbin cores. |
| CMTS |
| cable modem termination system |
| CO |
| Central Office. A local telephone company office which connects to the main system where circuit switching of customer lines occurs. |
| Coder/Decoder (Codec) |
| Equipment to convert between analog and digital information format. Also may provide digital information format. Also, may provide digital compression functions. |
| Coercive Force (HC) |
| The value of magnetizing force required to reduce the flux density to zero. |
| COFDM |
| code orthogonal frequency-division multiplexing |
| Coil |
| Another name for an inductor. |
| Coils |
| Another name for inductors. |
| Common |
| Conductive path used as a return for two or more circuits. Common is often used interchangeably with ground, which is technically not correct unless it is connected to earth. Also see Ground. |
| Common Carrier |
| Licensed utility that provides communications services at government-regulated rates. |
| Common Mode Current |
| A current conduction mode in which currents, present in two or more conductors, are flowing in phase and with equal magnitude within the conductor. |
| Common Mode Filter (or Choke) |
| An often used type of EMI filter which is wound in such a way that the phasing of the conductors will present a high impedance to common mode current (or noise) while presenting a low impedance to the desired signal. |
| Common Mode Noise(CoEv) |
| Noise or electrical interference that is common to both electrical lines in relation to ground. |
| Common Mode Noise(Raychem) |
| Noise component that is common to both the converter output and return lines with respect to the input common. |
| Common Mode Type I |
| On a single phase Wye bus, the conduction mode in which phase, neutral, and ground currents are in phase. The return current path is through the ground plane and the case. |
| Common Mode Type II |
| On a single phase Wye bus, the conduction mode in which phase and neutral currents are in phase, but the green wire currents are the return path, thus 180¡ out of phase. |
| Common Mode Voltage |
| The voltage that drives directed common mode (noise) current. |
| Compression |
| Reducing the size of a data set to lower the bandwidth or space required for transmission or storage. |
| Concentrator |
| Device that serves as a wiring hub in star-topology network. Sometimes refers to a device containing multiple modules of network equipment. |
| Conditioned Analog Line |
| Analog line to which devices have been added to improve the electrical signal. |
| Conduction Cooled |
| Cooling a converter via a solid material. Cools a power converter by adding a heat sink or attaching the module to the system chassis. |
| Conductive Polymer |
| A dispersion of conductive particles in an insulating organic polymer. |
| Continuous Shield |
| See six-sided shielding. |
| Control Winding |
| The winding on a mag amp or saturable reactor used to control the amount of magnetic energy the core will absorb before saturating. |
| Controller (USB) |
| Device that provides the direct interface between the power switch device and the microprocessor. Enable and flag pin outputs connect directly into the power switch device. |
| Convection Cooled |
| Cooling of a converter via the movement of air over the surface of its heat dissipating components. Free-air convection means that the natural movement of air (unassisted by a fan or blower) is sufficient to maintain a converter within specified operating limits. |
| Copper Loss(CoEv) |
| The power lost by current flowing through the winding. The power loss is equal to the square of the current (I) multiplied by the resistance (R) of the wire (I2R). This power loss is realized in the form of heat. |
| Copper Loss(Raychem) |
| The power lost by current flowing through the winding. The power loss is equal to the square of the current multiplied by the resistance of the wire (1^2*R). This power loss is transferred into heat. |
| CopperOptics |
| A PairGain trademark referring to the functionality of the company's xDSL technology. In essence, with PairGain xDSL products, users can achieve fiber optic-quality signal transmission over copper cable. |
| Core |
| Magnetic material placed withing and around a coil to provide a path of lower reluctance for magnetic flux. |
| Core Constant (C1) ([cm-1 ; mm-1]) |
| The summation of the magnetic path length of each section of the circuit divided by the corresponding area of the same section. |
| Core Constant (C2) ([cm-3 ; mm-3]) |
| The summation of the magnetic path length of each section of the magnetic circuit divided by the square of the corresponding magnetic area of the same section. |
| Core Constant (CX, cm-Ô) |
| The summation of the magnetic path lengths of each section of the magnetic circuit divided by the corresponding magnetic area of the same section. |
| Core Losses |
| Losses in the core made up from three main components: hysteresis, eddy current, and residual losses. These are caused by an alternating magnetic field in the core material. The losses are a function of the operating frequency and the total magnetic flux swing. These losses vary considerably from one magnetic material to another. Applications such as high power and frequency switching regulators require careful attention to core selection to yield the highest inductor performance by keeping the core losses to a minimum. |
| Core Losses |
| Core losses are caused by an altering magnetic field in the core material. The losses aer a function of the operating frequency and the total magnetic flux swing. The total core losses are made up of three main components: Hysteresis, eddy current and residual losses. These losses vary considerably from one magnetic material to another. Applications such as higher power and higher frequency switching regulators require careful core selection to yield the highest inductor performance by keeping the core losses to a minimum. |
| Core Saturation |
| See Saturation Current. |
| Core Saturation |
| See saturation current. |
| CPE |
| Customer Premises Equipment-Terminating equipment, such as terminals, phones, routers and modems, supplied by the phone company, installed at customer sites, and connected to the phone company network |
| Critical Rate of Rise of Off-State Voltage |
| Maximum voltage rate of rise that will not cause a SiBar device to turn on. |
| Critical Rate of Rise of On-State Current |
| Maximum current rate of rise a SiBar device can withstand without damage. |
| Cross Regulation |
| For a multiple output converter, the change in voltage on one output (expressed as a percent) caused by a load change on another output. |
| Crosstalk |
| Line static that can occur when wire pairs within the same bundles are used for separate signal transmission. Especially evident with repeated T1/E1 transmission. |
| Crowbar |
| Circuit that crowbars or rapidly shuts down a converters output if a preset voltage level is exceeded. The circuit places a low resistance shunt across the output when an overvoltage condition exists. |
| CSU/DSU |
| Channel Service Unit/Data Service Unit- A digital interface unit that connects end user equipment to the local digital telephone loop. |
| Cuk Converter |
| Variation of the "buck-boost" converter that produces very low output ripple. Used primarily in applications that do not require input/output isolation. Also see Flyback Converter. |
| Curie Temperature(CoEv) |
| The temperature at which a ferrite material loses its magnetic properties. The coreÕs permeability typically increases dramatically as the core temperature approaches the curie temperature, which causes the inductance to increase. The permeability drops to near unity at the curie temperature, which causes the inductance to drop dramatically. The curie point is the temperature at which the initial permeability (µi) has dropped to 10% of its value at room temperature. |
| Curie Temperature(Raychem) |
| The temperature above which a ferrite core loses its magnetic properties. The core's permeability typically increases dramatically as the core temperature approaches the curie temperature which causes the inductance to increase. The permeability drops to near unity at the curie temperature which causes the inductance to drop dramatically. The curie point is the temperature at which the initial permeability has dropped to 10% if its original value at room temperature. |
| Current Density |
| The amperes per unit of cross section in the conductor. This is commonly measured in circular mils per amp (cm/a). |
| Current Foldback |
| See foldback current limiting. |
| Current Limit |
| Maximum steady-state current level at which the power switch output is regulated in response to an overcurrent fault. |
| Current Limit Knee |
| On a plot of output voltage vs current, the point at which current begins to limit (or foldback). |
| Current Limiting |
| Feature that protects the converter (or load) from damage under overload conditions. The maximum converter output current is automatically limited to a predetermined safe value. If the converter is specified for auto restart, normal operatoin is automatically restored when overload condition is removed. |
| Current Mode Control |
| Control method used with switching converter topologies. A dual loop control circuit adjusts the PWM operation in response to a measured output current. |
| Current Rating (ldc) |
| Is the maximum recommended DC current for the inductor. Expressed in milliamps (mA) or amps (A) maximum. This is limited by the allowable temperature rise. |
| Current Transformer |
| Usually used in a sensing device, current transformers customarily have a one turn primary. The number of secondary turns is determined by the sensitivity required and is terminated with a resistor. Toroidal in shape, cores of silicon steel, nickel alloy, or ferrite are used. Choice of core material influences cost and accuracy. |
| Current,Hold |
| The largest steady state current that, under specified ambient conditions, can be passed through a PolySwitch device without causing the device to trip. For SiBar devices, the current at which the device resets to a high-impedance state once the surge current dissipates. See also Hold Current. |
| Synonyms: IH,IHOLD |
| Current,Maximum Interrupt |
| The highest fault current that can safely be used to trip a PolySwitch device under specified conditions. Typically the lower the voltage dropped across the PolySwitch device in its tripped state, the higher the maximum interrupt current. Maximum interrupt currents are usually shown in this Databook at the maximum voltage. It may be possible to use a PolySwitch device at a higher interrupt current, but each such use must be individually qualified. |
| Synonyms: Imax |
| Current,Normal Operating |
| The highest steady state current that is expected to flow in a circuit under normal operating conditions. At the maximum ambient operating temperature of the circuit, the hold current of a PolySwitch device used to protect the circuit is typically greater than the normal operating current. |
| Current,Operating Range |
| The range of normal operating currents in a circuit containing a PolySwitch device. Typically the hold current of the PolySwitch device should be greater than the top of the operating current range. |
| Current,Trip |
| The smallest steady state current that, if passed through a PolySwitch device, will cause the device to trip, under specified conditions. |
| Synonyms: IT |
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| D Channel |
| Full duplex 16 kbps (basic rate) or 64 kbps (primary rate) ISDN channel. |
| D-ISDN |
| broadband integrated services digital network |
| Data Circuit-terminating Equipment |
| Equipment that resides at the customer end of a transmission link and provides all necessary termination function for that link. May be owned by the customer or by the service provider. |
| Data Terminal Equipment (DTE) |
| The part of a data station that serves as a data source, destination, or both, and that provides for the data communications control function according to protocol. DTE includes computers, protocol translators, and multiplexers. |
| DBS |
| direct broadcast satellite |
| DC Bias |
| Direct current (DC) applied to the winding of a core in addition to any time-varying current. Inductance with DC bias is a common specification for powder cores. The inductance will Òroll offÓ gradually and predictably with increasing DC bias. |
| DC Filter |
| A filter circuit that removes the AC ripple from a mostly DC current. Usually this is done by using an inductor and capacitor together. |
| DC Stress |
| Annealing a magnetic material in the presence of a DC magnetic field to enhance magnetic properties. |
| DC-DC Converter(CoEv) |
| A circuit or device that converts a DC input voltage (usually unregulated) to a regulated DC output voltage. The output voltage may be lower, higher, or the same as the input voltage. Switching regulator DC-DC circuits most often require an inductor or transformer to achieve the regulated output voltage. Switching regulator circuits can achieve a higher level of power efficiency when compared to non-switching techniques. |
| DC-DC Converter(Raychem) |
| A circuit or device that converts a DC input voltage to a regulated output voltage. The output voltage may be lower, higher or the same as the input voltage. Switching regulator DC-DC circuits can achieve a higher level of power efficiency when compared to non-switching techniques (Also see Boost Regulator and Buck Regulator). |
| DCE |
| Data Communications Equipment(EIA expansion) or Data Circuit-Terminating Equipment (CCITT expansion)- The devices and connections of a communications cicuit with the end device (data terminal equipment). A modem can be considered a DCE. |
| DCR (DC Resistance)(CoEv) |
| The resistance of an inductor to a DC current (not alternating). The DCR is most often minimized in the design of an inductor. The unit of measure is the Ohm, and is usually expressed as a maximum rating. |
| DCR (DC Resistance)(Raychem) |
| The resistance of the inductor winding measured with no alternating current. The DCR is most often minimized in the design of an inductor. The unit of measure is ohms and it is usually specified as a maximum rating. |
| Decoupling |
| Refers to a magnetic circuit where comparatively more of the flux generated by the MMF fringes around the magnetic material instead of entering it. |
| Dedicated Line |
| A transmission circuit installed between two sites of a private network and "open," or available, at all times. |
| Demagnetization Curve |
| That portion of the hysteresis loop that lies between the residual induction point (BR) and the coercive force point (HC). |
| Demagnetized |
| A material condition where a ringing AC field has reduced the remnant induction to or near zero. A ringing AC field is a continually decreasing sinusoidal field. A pulsed DC field can be used to achieve gross demagnetization, but with much effort and with residual local magnetization. |
| Demodulation |
| Opposite of modulation, the process of retrieving data from a modulated carrier wave. |
| Density |
| See Power Density. |
| Derating |
| For a DC-DC converter, the specified reduction in output power required for operation at elevated temperatures. The most common operating temperature reange specified. Also see Convection Cooled. |
| Dial up |
| A type of communication that is established by a switched-circuit connection using the telephone network. |
| Dielectric |
| Material used to prevent two points in a electrical circuit from becoming conductively connected. Sometimes called a dielectric barrier. |
| Dielectric Strength - Electric Strength - Hipot |
| The two most important, basic, and unique features that signal-isolation transformers provide are balance and physical separation, i.e. a dielectric barrier. The physical separation of the primary and secondary windings (or line-side and chip-side windings) allows sensitive low-voltage circuits to be safely electromagnetically connected to circuit nodes exposed to high voltage potentials without a direct conductive path.%0aThe voltage rating of a transformer is called out by its dielectric strength level in VACRMS or VDC. The transformer is guaranteed to isolate the primary and secondary windings from high-voltage transients below this rated level. The typical dielectric level for most telecom applications is 1500VACRMS for a one minute duration.%0aAt some voltage potential, a leakage current will begin to flow through the protective insulation. When the magnitude of this current exceeds a predefined level (typically 500µA), Insulation Breakdown or Dielectric Breakdown is said to have occurred.%0aAs per UL1950 (5.3.2):%0a"Insulation breakdown is considered to have occured when the current which flows as a result of the application of the test voltage rapidly increses in an uncontrolled manner, i.e. the insulation does not restrict the flow of the current. Corona discharge or a single momentary flashover is not regarded as insulation breakdown." |
| Dielectric Withstand Voltage (DWV)(CoEv) |
| The voltage level at which the dielectric breaks down, allowing conduction between isolated conductors or between a conductor and the core. Isolation, or hipot is the ability of a transformer to withstand a specific breakdown voltage between the primary and secondary windings. |
| Dielectric Withstand Voltage(Raychem) |
| Maximum voltage an insulating material can withstand before breaking down (suffering punch through or arcing). |
| Differential Mode |
| A current conduction mode in which currents, relative to two conductors, are flowing 180¡ out of phase, with equal magnitude within the conductors. |
| Differential Mode Current |
| The intended signal currents that are equal and oppositely directed on pairs of signal and return (ground) conductors. |
| Differential Mode Noise(CoEv) |
| Also known as normal-mode noise. It is the electrical interference that is not common to both lines, but is present between both lines. |
| Differential Mode Noise(Raychem) |
| Noise component measured between two points with respect to a common point (minus common mode noise). |
| Differential Mode Voltage |
| The voltage that drives equal and oppositely directed currents to achieve an intended circuit function. The source of differential mode current. |
| Digital Signal 0 (DS-0) |
| North American Digital Hierarchy signaling standard for transmission at 64 kbps. (2) Digital Signal Level 0 is the worldwide standard transmission rate (64 kbps) for PCM digitized voice channels. 24 DSOs exist in each DSI (T1) signal. |
| Digital Signal 1 (DS-1) |
| North American Digital Hierarchy signaling standard for transmission sat 2.544 Mbps. Supports 24 simultaneous DS-O signals. Term often used interchangeably with T-1, although DS-1 signals may be exchanged over other transmission systems. |
| Disable |
| The act of de-asserting the enable signal to turn off the device. In the case of an EN low device, the EN signal must fall below the typical threshold voltage of 1.5V. |
| Disaccommodation (DF) |
| The proportional decrease of permeability after a disturbance of a magnetic material, measured at a constant temperature, over a given time interval. The resultant permeability after magnetic conditioning divided by the permeability of the first measurement times log10 of the ratio of time interval. |
| Discrete Air Gap |
| Mechanical air gap created by a small number of breaks in the magnetic path. In a standard C-core this number is generally two, a standard E-core is generally three, etc. |
| Distortion |
| Any deviation from the mathematical ideal of a real-world periodic waveform, which is specified as a percent of the desired signal. Distortion can be expressed mathematically in terms of the harmonics of the fundamental frequency. This parameter is of considerable importance in instrumentation transformers. |
| Distributed Air Gap |
| A major feature of iron powder cores. It is the cumulative effect of many small gaps distributed evenly throughout the core. In a typical MPP core, the number of separate air gaps results from the use of powder to construct the core and numbers in the millions. The result is minimal fringing flux density compared to a core with one or two discrete air gaps in the magnetic path. |
| Distributed Capacitance(CoEv) |
| In the construction of an inductor, each turn of wire or conductor acts as a capacitor plate. The combined effects of each turn can be presented as a single capacitance known as the distributed capacitance. The capacitance is in parallel with the inductor. This parallel combination will resonate at some frequency, which is called the self-resonant frequency (SRF). Lower distributed capacitance for a given inductance will result in a higher SRF and vise versa. |
| Distributed Capacitance(Raychem) |
| In the construction of an inductor, each turn of wire or conductor acts as a capacitor plate. The combined effects of each turn can be presented as a single capacitance known as the distributed capacitance. The capacitance is in parallel with the inductor. This parallel combination will resonate at some frequency which is called the self-resonant frequency (SRF). Lower distributed capacitances for a given inductance value will result in a higher SRF value for the inductor and vice versa (Also see SRF) |
| Distributed Power |
| System level architecture in which converters operating from a central power bus provide localized power (and various voltage levels) to individual subassemblies/components. The type of power distribution system used is highly dependent upon the needs of a particular application. |
| DLEC |
| digital local carrier |
| DMT |
| Discrete Multitone. In DMT, a large number of low-rate carrier frequencies are QAM-modulated at a low rate to transmit a single high-rate data stream. DMT is used for ADSL and proposed for VDSL. |
| DOCSIS |
| Data Over Cable System Interface Specification |
| Drift |
| Change in the output voltage of a converter over a specified period of time. All other operating parameters (load, line, etc.) are assumed to be held constant. Often specified as starting after a warm up period. |
| Drop Cable |
| A cable that connects a network device such as a computer to a physical medium such as an Ethernet network. Drop cable is also called transceiver cable because it runs from the network node to a transceiver (a transmit/receiver) attached to the trunk cable. |
| DSL |
| Digital Subscriber Line- Another name for an ISDN BRI channel. Operated at the Basic Rate Interface (with two 64 kbps circuit switched channels and one 16 kbps packet switched channel), the DSL can carry both voice and data signal at the same time, in both directions, as well as the signaling data used for call information and customer data. |
| DSLAM |
| digital subscriber line access multiplexer |
| DSP |
| Digital Signal Processor- The processing of signal transmission using digital techniques. |
| Duty Cycle |
| Maximum recommended usage (cycles) per unit of time. Alternatively, the percent of the ÒonÓ time of a square wave in a switching power supply. |
| DWDM |
| dense wavelength division multiplexing |
| Dynamic Load |
| Output load that changes rapidly. Normally specified as both a load change value and a rate of change. |
| Dynamic Response |
| Output overshoot that occurs when the converter output load is turned on/off or abruptly changed. This overshoot gives the high frequency output impedance of the converter. Also see Output Impedance. |
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| E1 |
| The term for a digital facility used for transmitting data over a telephone network at 2.048 Mbps. The European equivalent of T1. |
| E3 |
| The highest transmission rate generally available in the European digital infrastructure (34 Mbps). |
| Echo Cancellation |
| Process by which a transmitter/receiver cancels out the transmitted signal as to "hear" the received signal better. |
| Eddy Current Losses(CoEv) |
| Core losses associated with the electrical resistivity of the magnetic material and induced voltages within the material. Eddy currents are inversely proportional to material resistivity and proportional to the rate of change of flux density. Eddy current losses are present in both the magnetic core and windings of an inductor. Eddy currents in the winding, or conductor, contribute to two main types of losses: losses due to proximity effects and skin effects. As for the core losses, an electric field around the flux lines in the magnetic field is generated by alternating magnetic flux. This will result in eddy currents if the magnetic core material has electrical conductivity. Losses result from this phenomenon since the eddy currents flow in a plane that is perpendicular to the magnetic flux lines. Eddy current and hysteresis losses are the two major core loss factors. Eddy current loss becomes dominant in powder cores as the frequency increases. |
| Eddy Current Losses(Raychem) |
| Eddy current losses are present in both the magnetic core and winding of an inductor. Eddy currents in the winding (or conductor) contribute to two main types of losses: losses due to proximity effects and skin effects. As for the core losses, an electric field around the flux lines in the magnetic field is generated by alternating magnetic flux. This will result in eddy currents if the magnetic core material has electrical conductivity. Losses result from this phenomenon since the eddy currents flow in a plane that is perpendicular to the magnetic flux. |
| EDGE |
| Enhanced Data rates for Global Evolution |
| Effective Area (AE) |
| For a magnetic core of a given geometry, the magnetic cross-sectional area that a hypothetical toroidal core of the same material properties would possess to be the magnetic equivalent to the given core. |
| Effective Length (le) |
| For a magnetic core of a given geometry, the magnetic length that a hypothetical toroidal core of the same material properties would possess to be the magnetic equivalent to the given core. |
| Effective Permeability (µe) |
| For a magnetic circuit constructed with an air gap, or gaps, the permeability of a hypothetical homogeneous material that would provide the same reluctance, or net permeability. |
| Effective Volume (Ve) |
| For a magnetic core of a given geometry, the magnetic volume that a hypothetical toroidal core of the same material properties would possess to be the magnetic equivalent to the given core. |
| Efficiency |
| Ratio of total output power to input power expressed as a percentage. Efficiency is derived by the equation: Efficiency (%) Efficiency is normally measured at full rated output power and nominal input line conditions. |
| Electromagnetic Interference (EMI) |
| An unwanted electrical energy in any form. EMI is often used interchangeably with ÒnoiseÓ and ÒinterferenceÓ. |
| Electrostatic Discharge (ESD) |
| Current produced by two objects having a static charge when they are brought close enough to produce an arc or discharge. |
| Electrostatic Shield |
| See Faraday Shield. |
| EMI |
| EMI is an acronym for Electromagnetic Interference. It is unwanted electrical energy in any form. EMI is often used interchangeably with Noise. |
| EMI Filter |
| Filter placed at the input to an off-line converter that minimizes the effect of EMI on the converter and the associated system. |
| Enable |
| The act of asserting the enable signal to turn on the device. In the case of an EN low device, the EN signal must exceed the typical threshold voltage of 1.5V. |
| Synonyms: EN |
| Enable High/Low |
| Some USB controller ships have enable logic that requires the power switch to be active low while others require the switch to be active high. This signal will be connected to the enable pin of the device selected. |
| Enclosure |
| Case or container used to package a converter. Typically, converters are packaged in small plastic or metal. |
| Energy Storage (.5LI2) |
| The amount of magnetic energy which can be stored in a given inductor in microjoules. It is the product of one half the inductance required in microhenries (µH) and the current (I) squared in amperes. |
| Energy Storage Inductors |
| Inductors used for energy storage, generally in power conversion rather than filtering or tuning. |
| Enterprise Network |
| A large typical corporate network under the auspices of one organization. |
| Equivalent Series Inductance (ESL) |
| Inductance in series with an "ideal" capacitor. Sources include leads, terminals, electrodes etc. |
| Equivalent Series Resistance (ESR) |
| Resistance in series with an "ideal" capacitor. Sources include lead resistance, terminal losses, etc. An important specification for high frequency applications. |
| Error Amplifier |
| Operational or different amplifier used in the control feedback loop of a converter. The amplifier produces an error voltage when the output (tapped off a voltage divider network) differs from a reference voltage. This error voltage is used to adjust the oepratioin of the PWM so as to correct the sensed output voltage. Sometimes called a Reference Amplifier. |
| Ethernet |
| A baseband LAN specification invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation. Ethernet networks operate at 10 Mbps using CSMA/CD to run over coaxial cable. Ethernet has become a series of standards produced by IEEE referred to as IEEE 802.3. |
| Excitation Current |
| The current required to overcome the losses in a core, which begins to produce magnetic energy (or flux) in an inductor. |
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| Failure Mode |
| Reason for which a converter either does not meet or stops meeting its specified parameters. |
| Fan Cooled |
| See Forced Air Cooling. |
| Faraday Shield |
| Electrostatic shield that reduces coupling capacitance in transformers. The shield, which effectively reduces output common mode noise, is placed between the primary and secondary windings of a transformer. |
| Fault Mode Current |
| Input current drawn by a converter when the output is shorted. |
| FDM |
| frequency division multiplexing |
| FDMA |
| frequency division multiple access |
| Federal Communications Commission (FCC) |
| US government agency that sets standards for, and governs the testing oc conducted and radiated emissions. These are system level standards, but they are typically used in specifying converters. Also see Electromagnetic Interference. |
| Feed Forward |
| Method of improving line regulation by directly sensing the input voltage of the converter. Also see Line Regulation. |
| Ferrite Core |
| Ferrite is a magnetic material which consists of a mixed oxide of iron and other elements that are made to have a crystalline molecular structure. The crystalline structure is created by firing the ferrite material at a very high temperture for a specified amount of time and temperature profile. The general composition of ferrites is xxFe204 where xx represents one or several metals. The most popular metal combinations are manganese and zinc(MnZn) and nickel and zinc (NiZn). These metals can be easily magnetized. |
| Ferrite/Ferrite Cores |
| Ferrite is a magnetic material that consists of a mixed oxide of iron and other elements that are made to have a crystalline molecular structure. Firing the ferrite material at a very high temperature for a specified amount of time and temperature profile creates the crystalline structure. The general composition of ferrite is xxFe2O4 where xx represents one or several metals. The most popular metal combinations are manganese and zinc (MnZn) and nickel and zinc (NiZn). These materials can be easily magnetized with little coercive force. Available in a variety of shapes and sizes, these ceramic magnetic cores are composed of ferric oxide and a combination of manganese, zinc, or nickel. The shapes EE, PQ, UU, ETD, and dual-slab are used for high frequency power applications. Telecommunications and low power applications use pot cores, touch tone cores, EP, and RM. Slugs, rods, and beads are used for radio frequency applications. |
| Ferromagnetism |
| Ferromagnetic materials have atomic fields that align themselves parallel with externally applied fields creating a total magnetic field much greater than the applied field. Ferromagnetic materials have permeabilities much greater than air (1). Above the curie temperature, the ferromagnetic materials become paramagnetic. |
| Ferroresonat Transformer |
| Transformer in which part of the core is driven in saturation by a resonant tank circuit. The output of the transformer, taken from the saturated protion, is relative immune to variations in input voltage. |
| Fiber Optic Cable |
| A transmission medium that uses glass or plastic fibers, rather than copper wire, to transport data or voice signals. The signals is imposed on the fiber via pulses (modulation) of light from a laser or a light-emitting diode (LED). Because of its high bandwidth and lack of susceptibility to interference, fiber-optic cable is used in long-haul or noisy applications. |
| Fiber Optics |
| A method for the transmission of information (sound, pictures, data). Light is modulated and transmitted over high purity, hair-thin fibers of glass. The bandwidth capacity of fiber optic cable is much greater than that of conventional cable or copper wire. |
| Field Strength (H) |
| The parameter characterizing the amplitude of AC or DC field strength. The magnitude of current, number of turns, and winding geometry determine field strength. |
| Filter(CoEv) |
| A circuit or device whose purpose is to control electrical energy at a given frequency or over a range of frequencies. Groups of passive components are commonly used to construct many types of filters, including resistors, capacitors, and inductors. |
| Filter(Raychem) |
| A circuit or device whose purpose is to control electrical energy at a given frequency or over a range of frequencies. Groups of passive components are commonly used to construct many types of fileters. These passive components include resistors, capacitors and inductors. |
| Flag |
| Power switch output that provides the USB controller the power switch device status. When FLG = High, the output MOSFET allows power to flow from the supply rail. |
| Synonyms: FLG |
| Flag delay time |
| Design feature that delays the FLG notification signal in response to an abnormal condition (hot plug event, overcurrent surge, overtemperature condition). This feature minimizes unnecessary nuisance ÒtripsÓ caused by the inrush current of high capacitive loads. |
| Floating Output |
| Converter output that ungrounded and not referenced to another output. Typically, floating outputs are fully isolated and may be referenced positive or negative by the user. Outputs that are not floating share common return and as such, are referenced to one another. |
| Flux Density (B) |
| The corresponding parameter for the induced magnetic field in an area perpendicular to the flux path. Flux density is determined by the field strength and permeability of the medium in which it is measured. |
| Flux Transfer Ratio |
| The numeric amount of flux intercepted by the secondary winding and the total flux created by the applied ampere-turns. |
| Flux(CoEv) |
| In magnetics, the magnetic field. Flux implies flow, which is not the case in magnetics. That is, no one has measured a magnetic ÒflowÓ. Flux is represented conceptually as Òmagnetic lines of forceÓ. Flux density is measured in Gauss or Teslas. |
| Flux(Raychem) |
| Product of the average component of magnetic induction perpendicular to any given surface in a magnetic field by the area of that surface, expressed in webers. |
| Flyback |
| Actually an isolated storage inductor, a flyback transformer is a combination of an isolating transformer, output inductor, and flywheel diode. These use a gapped core and have a power handling capability of 100VA. Storing energy in the gap when the switch is on and delivering energy to the load when the switch is off, they do not perform like standard transformers. |
| Flyback Converter |
| Also called a "buck-boost" converter, this topology typically uses a single transistor switch and eliminates the need for an output inductor. Energy is stored in the transformer primary during the first half of the switching period when the transistor switch is on. During the second half or "flyback" period when the transistor is off, this energy is tranferred the transformer secondary and load. Also see Boost Regulator, Buck Regulator, Bridge Converter, Forward Converter, Push-Pull Converter and Resonant Converter. |
| Flyback Transformer |
| Transformer used in a flyback power supply. Also called horizontal output transformer. |
| Foldback Current Limiting |
| Converter protection technique in which the circuit is protected under overload conditions by reducing the output current as the load approaches short circuit. This minimized internal power dissipation under short circuit conditions. |
| Forced Air Cooling |
| Use of a fan (or other air moving equipment) within a (sub) system to move air across heat producing components in order to reduce the ambient temperature. Also called forced convection. |
| Forward Converter |
| Also called a "Buck-Derived" converter, this topology, like the flyback converter, typically uses a single transistor switch. Unlike the flyback converter, energy is tranferred to the transformer secondary while the transistor switch is "on", and stoed in a output inductor. See Boost Regulator, Buck Regulator, Bridge Converter, Flyback Converter, Push Pull Converter and Resonant Converter. |
| Forward Converter Transformer |
| A transformer which operates by transferring power to the load during the on time and resetting in the off time. Since this transformer only transfers power during half of an input cycle it is required to be larger than a push-pull transformer for example. |
| FPGA |
| field-programmable gate array |
| Fractional T1 |
| A WAN communications service that provides the user with some portion of a T1 circuit which has been divided into 24 separate 64 kbps channels. |
| Frame Relay |
| A streamlined packet switching protocol designed to provide high-speed frame or packet switching with minimal delay and efficient bandwidth usage. |
| Free Convection |
| Operating environment where the natural movement of air (unassisted by fans or blowers) maintains the power module within its operating limits. Also called natural convection. |
| Frequency of Operation |
| See Switching Frequency |
| Fringing Fields or Fringing Flux |
| The field(s) associated with the divergence of the flux from the shortest path between poles in a magnetic circuit. Where flux passes through a high permeability into a lower permeability material, the flux redistributes and tends to have a Òbarreling effectÓ between the two poles. See also leakage flux. |
| Full Bridge |
| Four power switches are used in a full bridge and usually utilize a single primary winding. Full supply voltage is obtained in both directions and utilizes the core and windings more effectively. Voltage on the switches does not exceed the supply voltage. |
| Full Bridge Converter |
| Converter topology that typically operates as forward converter but uses a bridge circuit, consisting of four switching transistors, to drive the transformer primary. Also see Bridge Converter. |
| Full Load |
| Maximum value of output load specified for a converter under continuous operating conditions. |
| Full Load Voltage |
| Variations in winding resistance, turns ratio, and leakage can cause minor discrepancies in output voltage, which is the full load voltage. |
| Full Winding |
| A winding for toroidal cores that will result in 45% of the coreÕs inside diameter remaining. |
| Full-Wave Rectifier |
| See Rectification |
| Functions |
| Class of devices designed to perform a specific task. Examples include USB internet cameras, joysticks, mice, and digital cameras. |
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| Ganged port protection |
| Protection method where one circuit protection device (or output) is used to protect more than one output port. |
| Gauss |
| The CGS unit of measurement for flux density. One Gauss is equal to 1 Maxwell per cm2. |
| Gigabits Per Second (Gbps) |
| 1,000,000,000 bits per second. A measure of transmission speed. |
| Gilbert |
| A unit of magnetomotive force in the CGS system. |
| GPRS |
| general packet radio service |
| Graded Cores |
| MPP and HF cores are graded into increments of permeability within their normal ±8% tolerance. It is expressed as a percent deviation from the nominal value. |
| Grain Oriented |
| Silicon steel or other granular magnetic material that has a preferred direction of magnetization. |
| Ground |
| Electrical connection that is made to earth (or to some conductor that is connected to earth). |
| Ground Loop |
| Condition caused when two or more system components share a common electrical ground line. A feedback loop is unintentionally induced, causing unwanted voltage levels. |
| GSM |
| global system for mobile communications |
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| Half Bridge |
| A dual, forward converter, using two power switches can also be called a half bridge. Power, which does not exceed the supply voltage, is delivered to the load only during half the input cycle. This design permits the use of a smaller transformer. |
| Half Bridge Converter |
| Converter topology that typically operates as a forward converter but uses a bridge circuit, consisting of two switching transistors, to drive the transformer. Also see Bridge Converter. |
| Half-Wave Rectifier |
| See Rectification. |
| Hall Effect Transducer |
| A device that produces a voltage output dependent upon an applied DC voltage and an incident magnetic field. The magnitude of the output is a function of the field strength and the angle of incidence with the Hall device. |
| Hard Magnetic Material |
| A ÒpermanentÓ magnet material that has an intrinsic coercivity generally greater than or equal to about 300 Oersteds. |
| HDSL |
| High-bit-rate Digital Subscriber Line- Designed to be a cost-effective method of delivering T1/E1 line speeds over unconditioned copper cable, without the use of repeaters. |
| Headend |
| The source end of a coaxial cable TV system. Often, the site for signal processing equipment essential to proper functioning of a cable system. |
| Heat Flux |
| Flow rate of heat across or through a material, typically given in W/cm2 |
| Heat Sink |
| Metal plate, extrusion, case, etc. used to transfer heat away from sensitive components and/or circuits. Also see Base Plate. |
| Henry |
| The unit for inductance. |
| Hiccup Mode |
| Operating mode triggered by an output fault condition (short-circuit)in which the converter cycles on and off the duty cycle of on time to off time maintains the interenal power dissipation at a safe level until the fault condition is corrected. |
| High Line |
| Maximum value of input line voltage specified for normal converter operaton. Also see Low Line and Input Voltage Range. |
| High Potential Test (Hi-Pot Test) |
| Test used to determine whether a converter passes its miminum breakdown voltage specification. Also see Breakdown Voltage. |
| High Q Filters |
| A filter circuit that exhibits a high Q factor. It is very frequency sensitive and filters out or allows to pass, only those frequencies within a narrow band. |
| Hold Current |
| The largest steady state current that, under specified ambient conditions, can be passed through a PolySwitch device without causing the device to trip. For SiBar devices, the current at which the device resets to a high-impedance state once the surge current dissipates. See also Hold Current. |
| Synonyms: IH,IHOLD |
| Hold Current Minimum |
| The minimum current required to maintain the device in the on-state. For SiBar thyristors, the current at which the device resets to a high-impedance state once the surge current dissipates. |
| Hold-Up Time |
| Period of time that a converter output remains operating within specification following the loss of input power. This is a more common specificatioin for AC/DC supplies. |
| Host |
| The root of the USB architecture which provides signal/data and power (for bus-powered peripherals). In a USB application, the Host is typically within the main CPU. |
| Hot Plug-In |
| A common requriement in distributed power systems wherein the power board must be capable of being connected/disconnected from the power bus without damage. Power board components must be protected against the resultant high inrush currents. |
| Hot-Plug |
| The act of making a connection to the output port of a functioning peripheral or host. USB architecture is designed to recognize the connected function and ÒenableÓ it by providing necessary power and loading all necessary drivers. |
| Hub |
| Class of USB equipment that attaches to the Host and provides additional USB output connections for other hubs or functions. May be classified as self-powered hubs or bus-and self-powered hubs. |
| Humidity Aging Test |
| A test described in RaychemÕs PS300 publication in which the resistance of a PolySwitch device at room temperature is measured before and after aging at an elevated temperature (e.g., 40¡C) and high humidity (e.g., 95% RH) for an extended time (e.g., 1000 hours). |
| Hysteresis and Hysteresis Loss |
| Hysteresis means to lag behind. This is the tendency of a magnetic material to retain its magnetization. Hysteresis causes the graph of magnetic flux density versus magnetizing force (B-H curve) to form a loop rather than a line. The area of the loop represents the difference between energy stored and energy released per unit of volume of material per cycle. This difference is called the hysteresis loss. |
| Hysteresis Loop |
| A closed curve obtained for a material by plotting corresponding values of flux density for the ordinate and magnetizing force for the abscissa when the material is passing through a complete cycle between definite limits of either magnetizing force or flux density. If the material is not driven into saturation it is said to be on a minor loop. |
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| IAD |
| integrated access devices |
| ICP |
| integrated communication provider |
| ID |
| Abbreviation for inside diameter. |
| IDSL |
| ISDN digital subscriber line |
| IH |
| The largest steady state current that, under specified ambient conditions, can be passed through a PolySwitch device without causing the device to trip. For SiBar devices, the current at which the device resets to a high-impedance state once the surge current dissipates. See also Hold Current. |
| Synonyms: IHOLD |
| IHOLD |
| The largest steady state current that, under specified ambient conditions, can be passed through a PolySwitch device without causing the device to trip. For SiBar devices, the current at which the device resets to a high-impedance state once the surge current dissipates. See also Hold Current. |
| Synonyms: IH |
| ILEC |
| incumbent local exchange carriers (formerly RBOC) |
| Imax |
| The highest fault current that can safely be used to trip a PolySwitch device under specified conditions. Typically the lower the voltage dropped across the PolySwitch device in its tripped state, the higher the maximum interrupt current. Maximum interrupt currents are usually shown in this Databook at the maximum voltage. It may be possible to use a PolySwitch device at a higher interrupt current, but each such use must be individually qualified. |
| Impedance(CoEv) |
| The total resistance to flow of current, including both the AC and DC component. The DC component is simply the DC resistance of the winding. The AC component of the impedance includes the inductor reactance, which is written XL = 2ÄL. |
| Impedance(Raychem) |
| The impedance of an inductor is the total resistance to the flow of current, including the AC and DC component. The DC component of the impedance is simply the DC resistance of the winding. The AC component of the impedence includes the inductor reactance. The following formula calculates the inductive reactance of an ideal inductor (i.e. one with no losses) to a sinusoidal AC signal. (Z |
| Incremental Current(CoEv) |
| The DC bias current flowing through an inductor which causes an inductance drop of 5% from the initial zero DC bias inductance value. This current level indicates where the inductance can be expected to drop significantly if the DC bias current is increased further. This applies mostly to ferrite cores in lieu of iron powder. These core materials exhibit ÒsoftÓ saturation characteristics, which means their inductance drop from higher DC levels is much more gradual than ferrite cores. The rate at which the inductance will drop is also a function of the core shape. |
| Incremental Current(Raychem) |
| The DC bias current flowing through the inductor which causes an inductance drop of 5% from the initial zero DC bias inductance value. This current level indiciates where the inductance can be expected to drop significantly if the DC bias current is increased further. This applies mostly to ferrite cores in lieu of powdered iron. Powdered iron cores exhibit "soft" saturation characteristics. this means their inductance drop from higher DC levels is much more gradual than ferrite cores. The rate at which the inductance will drop is also a function of the core shape, i.e. air gap (Also see Saturation Current). |
| Incremental Permeability (µinc) |
| The permeability of a magnetic material about a specified operating point and applied magnetic field strength, especially under DC bias conditions. The incremental permeability is expressed as the slope of the B-H characteristic about the given operating point (dB/dH). |
| Individual Port Protection |
| Protection method where each output is protected by one circuit protection device (or output). For devices with multiple outputs per device, isolation is provided so that a port can respond to a fault condition without impacting the performance of the other port(s). |
| Inductance Factor (AL) |
| The inductance rating of a core in nanoHenries per turn squared (nH/N2) based on a peak flux density of 10 gauss (1 milliTesla) at a frequency of 10 kHz. An AL value of 40 would produce 400µH of inductance for 100 turns and 40mH for 1000 turns. |
| Inductance(CoEv) |
| That property of a circuit element which tends to oppose any change in the current flowing through it. The inductance for a given inductor is influenced by the core material, core shape and size, the turns count of the coil, and the shape of the coil. Inductors most often have their inductance values expressed in microHenries (µH) or milliHenries (mH). |
| Inductance(Raychem) |
| That property of a circuit element which tends to oppose any change in the current flowing through it. The inductance for a given inductor is influenced by the core material, core shape and size, the turns count of the coil and the shape of the coil. Inductors most oftern have their inductances expressed in microhenries (uH) |
| Inductor(CoEv) |
| A passive component designed to resist changes in current. Inductors are often referred to as AC resistors. The ability to resist changes in current and the ability to store energy in its magnetic field account for the bulk of the useful properties of inductors. Current passing through an inductor will produce a magnetic field, which induces a voltage, which opposes the field-producing current. This property of impeding changes in current is known as inductance. |
| Inductor(Raychem) |
| A passive component designed to resist changes in current. Inductors arc often referred to as AC Resistors. The ability to resist changes in current and the ability to store energy in its magnetic field account for the bulk of the useful properties of inductors. Current passing through an inductor will produce a magnetic field. A changing magnetic field induces a voltage which opposes the field-producing current. This property of impeding changes in current is known as inductance. The voltage induced across an inductor by a change of current is defined as: V |
| Initial Permeability (NO) |
| Permeability=u=B/H Initial permeability is that value of permeability when Bac=10gs. |
| Initial Permeability (µI) |
| The value of permeability at a peak AC flux density of 10 Gauss (1 milliTesla). |
| Initial Resistance |
| The resistance of a PolySwitch device under specified conditions (e.g., 20¡C), before connection into a circuit. Devices of a particular type will be delivered with a range of resistances; therefore, a minimum value, Rmin, and/or a maximum value, Rmax, are often given. |
| Synonyms: Resistance,Base Resistance,Rmin,or Rmax |
| Input Current |
| Current drawn from the input power bus by a converter when operating under nominal conditions |
| Input Line Filter(CoEv) |
| A power filter placed on the input to a circuit or assembly that attenuates noise introduced from the power bus. The filter designed to reject noise within a frequency band. Typically these are low pass filters, meaning they pass low frequency signals, such as the DC power, and attenuate the higher frequency signal, which consists of mainly noise. |
| Input Line Filter(Raychem) |
| A power filter placed on the input to a circuit or assembly that attenuates noise introduced from the power bus. The filter is designed to reject lise within a frequency band. Typically these filters arc low-pass filters meaning they pass low frequency signals such as the DC power and attenuate higher frequency signal which consist of mainly noise. Band pass or low pass filters are commonly made up of inductor and capacitor combinations. (Also see Noise, Attenuation, EMI and Pi-Filter). |
| Input Reflected Ripple Current |
| AC component (typically generated by the switching circuit) measured at the input of a converter. Given as a peak-to-peak or RMS value. |
| Input Surge Current |
| See Inrush Current. |
| Input Transient |
| Spike or step change in the input to a converter. Input transient protection circuits arc used to shield sensitive components (such as the semiconductor switch) from possible damage due to transients. |
| Input Voltage Range |
| Minimum and maximum input voltage limits within which a converter operates to specifications. Often given as a ratio of high line to low line (i.e. a range of 9VDC to 18VDC is 2:1) |
| Inrush Current |
| Maximum, instantaneous input current drawn by a converter at turn on. Also called Input Surge Current. |
| Inrush Current Limiting |
| Protection circuit that limits the current a converter draws at turn on. |
| Institute of Electrical and Electronic Engineers (IEEE) |
| Professional organization that defines network standards. IEEE LAN standards are the predominant LAN standards today, including protocols similar or virtually equivalent to Ethernet and Token Ring. |
| Insulated Gate Bipolar Transistor (IGBT) |
| Power semiconductor device available for use in power conversion circuits. |
| Insulation Resistance(CoEv) |
| The insulation properties of the insulating material measured in Ohms (_). |
| Insulation Resistance(Raychem) |
| Resistance offered by an insulating material to current flow. |
| Insulation(CoEv) |
| Properly insulated transformers can withstand severe environmental conditions and remain in service for many years. The temperature of operation and the dielectric withstanding voltage (hipot) will determine the type and amount of insulation needed. |
| Insulation(Raychem) |
| Non-conductive material used to protect and separate electronic components or circuits. |
| Interface |
| (1)The point at which two systems or pieces of equipment are connected. (2) A connection between two systems or devices. A shared boundary defined by common physical interconnection charasteristics, signal characteristics, and meanings of interchanged signals. |
| Internal Power Dissipation |
| Power dissipated (as heat) within the converter during normal operation. Primarily a function of the power handling capability and efficiency of the converter. Internal power dissipation is normally given as a maximum specification that cannot be exceeded without risking damage to the converter. |
| International Electrotechnical Commission (IEC) |
| Organization based in Switzerland that sets standards for electronic products and components. IEC does not conduct any testing; however, their standards have been adopted by many of the national safety/standards agencies. |
| Intranet |
| A private network that uses Internet software and standards. |
| Inverter |
| Power conversion circuit that converts DC to AC power |
| Inverter Transformer |
| A transformer driven in such a manner that an applied DC power is converted to AC power (square waveform). Quite often the core is driven into saturation to accomplish this function. |
| Iron-Core Coil/Transformer |
| Coil/transformer wound around an iron core to increase its inductance. At audio frequencies the iron core consists of laminations of silicon steel insulated from each other by varnish or shellac. At radio frequencies the core consists of powdered iron mixed in a binder which insulates the particles from each other. |
| Isc Max |
| The maximum short circuit a PolySwitch device is tested at the maximum operating voltage as specified. |
| ISDN |
| Integrated Services Digital Network- A CCITT networking standard devised to provide end-to-end, simultaneous handling of digitized voice and data traffic on the same link |
| Isolated Output |
| See Floating Output |
| Isolation |
| Electrical separation between the input and output of a converter; Normally determined by transformer characteristics and component spacing. Referring to isolation is specified in values of resistance (RISO, typically megohms) and capacitance (CISO, typically pF). |
| Isolation Capacitance |
| See Isolation. |
| Isolation Resistance |
| See Isolation. |
| Isolation Transformer |
| Transformer with a one-to-one turns ratio. connected between the a.c. power input to a piece of equipment and the a.c. line, to minimize shock hazard. |
| Isolation Voltage |
| Maximum voltage (AC or DC) that can be continuously applied between isolated circuits without a breakdown occuring. On converters, this is normally specified as input-output or input-case isolation. Minimum isolation voltage levels be maintained to meet most safety regulations. Also see Breakdown Voltage, High Potential and Isolation. |
| Isotropic |
| Having magnetic properties that are independent of the magnet orientation. Most magnetic materials are anisotropic as cast or powdered: each crystallite has a preferred direction of magnetic orientation. If the particles are not physically oriented during manufacture of the magnet, this results in random arrangement of the particles and magnetic domains, and produces isotropic magnetic properties. Conversely, orienting the material during the manufacture results in an anisotropic magnet. |
| ISP |
| Internet Service Provider |
| IT |
| The smallest steady state current that, if passed through a PolySwitch device, will cause the device to trip, under specified conditions. |
| ITU |
| International Telecommunications Union |
| IXC |
| Interexchange Carrier- (1)A long-distance telephone company offering circuit-switched, leased-line or packet-switched service or some combination. (2) Any individual, partnership, association, joint-stock company, trust, governmental entity or corporation engaged for hire in interstate or foreign communication by wire or radio, between two or more exchanges. |
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| Kilobits per second (kbps) |
| 1,000 bits per second. A measure of transmission speed. |
| Knee (of the demagnetization curve) |
| In the second and fourth quadrants of the hysteresis loop, some materials such as ferrite and rare earth exhibit a distinct ÒkneeÓ, or rapid change in slope of the intrinsic curve. The location of the knee is of interest to designers. |
| Kool Mu (r)(Raychem) |
| Kool Mu (r) is a magnetic material that has an inherent distributed air gap. The distributed air gap allowes the core to store higher levels of magnetic~ when compared to other magnetic materials such as ferrites. This characteristic allows a higher DC current level to flow through the inductor before the inductor saturates.%0aKool Mu (r) material is an alloy that is made up of basically nickel and iron powder (approx. 50% of each) and is available in several permeabilities. It has a higher permeability than powdered iron and also lower core losses. Kool Mu (r) is require to be pressed at much higher pressure than powdered iron material. The manufacturing process includes an annealing step that relieves the pressure put onto the powdered metals which restores their desirable magnetic properties. Thus, the powdered particles require a high temperature insulation as compared to powdered iron. Kool Mu (r) performs well in switching power applications. The relative cost is significantly higher than powdered iron. |
| Kool Mu¨(CoEv) |
| A magnetic material that has an inherent distributed air gap. The distributed air gap allows the core to store higher levels of magnetic energy when compared to other magnetic materials such as ferrite. This characteristic allows a higher DC current level to flow through the inductor before saturation occurs. Kool Mu¨ material is an alloy that is made up of basically nickel and iron powder (approximately 50% of each) and is available in several permeabilities. It has a higher permeability than iron powder and lower core losses. It must be pressed at a much higher pressure than iron powder material. Kool Mu¨ performs well in switching power applications. The relative cost is significantly higher than iron powder. |
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| Laminated Cores(CoEv) |
| Cores constructed by stacking multiple laminations on top of each other. The laminations are offered in a variety of materials and thicknesses. Some laminations are made to have the grains oriented to minimize the core losses and give higher permeabilities. Each lamination has an insulated surface that is commonly an oxide finish. Laminated cores are used in some inductor designs, but are more common in a wide variety of transformer applications. |
| Laminated Cores(Raychem) |
| Cores constructed by stacking multiple laminations on top of each other. The laminations are offered in a variety of materials and thicknesses. Some laminations are made to have the grains oriented to minimize the core losses and give higher permeabilities. Each lamination has an insulated surface which is commonly an oxide finish. Laminated cores are used in some inductor designs but are more common in a wide variety of transformer applications. |
| Laminations |
| Supplied in stamped letter shapes such as ÒEIÓ, ÒELÓ, ÒEEÓ, ÒFÓ, or ÒUIÓ, they are composed of silicon iron and nickel alloys. Audio and telecommunication transformers use nickel alloys, while silicon iron is generally used for line frequency power transformers. |
| LAN |
| Local Area Network- The means by which a local community of users and workgroups can share information and resources electronically. Many communications protocols are used to accomplish this, the most prevalent of which are Ethernet and Token Ring. |
| Last mile |
| A reference to the local loop, the distance between a local telco office and the subscriber, a distance actually about 0 to 3 miles (0 to 4 kilometers). |
| Leakage Current |
| Current flowing from input to output or input to case of an isolated converter at a specified voltage level. |
| Leakage Flux |
| The small fraction of the total magnetic flux in a transformer or common mode choke that does not contribute to the magnetic coupling of the windings. In a transformer with a single set of primary and secondary windings, the leakage flux is that portion of flux that is produced by the primary that does not link the secondary. The presence of leakage flux in a transformer or common mode choke is modeled as a small leakage inductance in series with each winding. It is measured at one winding with all other windings shorted. |
| Leakage Inductance |
| The inductance that does not link the primary in a coil. It is due to the leakage flux. |
| Leased Line |
| A transmission line reserved by a communication carrier for the private use of a customer. |
| LEC |
| local exchange carrier |
| LFM |
| Linear feet per minute, which is a measure of air velocity used to cool a power converter. |
| Life test |
| Reliability test in which a converter is operated (typically under accelerated conditions) over some period of time in order to approximate its life expectancy. |
| Lifeline POTS |
| A minimal telephone service designed to extend a "lifeline" to the telephone system in case of emergency, particularly when electric power is lost. |
| Line |
| Bus used to deliver power to the input terminals of a converter. Also see Bus, High Line and Low Line. |
| Line Code |
| Any method of converting digital information to analog form for transmission on a telephone line. 2B1Q, DMT, and CAP are all line codes. |
| Line Effect |
| See Line Regulation. |
| Line Regulation |
| Power supply regulation technique in which the regulating device (typically a transistor) is placed in series or parallel with the load. Voltage variations across the load are controlled by changing the effective resistance of the regulating device to dissipate unused power. Also see Series Regulator, Shunt Regulator and Post Regulation. |
| Line transient |
| See Input Transient. |
| Linear Material |
| Magnetic material that exhibits fairly constant permeability over a wide range of MMF. |
| Linear Power Transformer |
| Transformers that generally operate between 47Hz and 400Hz in power conversion, which alter the input voltage needed for the load. Linear power transformers are very inefficient. |
| Linear regulation |
| Power supply regulation technique in which the regulating device (typically a transistor) is placed in series or parallel with the load. Voltage variations across the load are controlled by changing the effective resistance of the regulating device to dissipate unused power. Also see Series Regulator, Shunt Regulator and Post Regulation. |
| Link |
| Physical connection between two nodes in a network. It can consist of a data communication circuit or a direct channel (cable) connection. Also an LED signal that indicates connection has been established. |
| Litz Wire |
| From the German word ÒlitzendraghtÓ, meaning to consist of a number of separate strands that are woven or bunched together such that each strand tends to take all possible positions in the cross section of the wire as a whole. The current through each individually insulated strand is divided equally since this wire design equalizes the flux linkages and reactance of the individual strands. In other words, a litz conductor has lower AC losses than compared to solid wire conductors, which becomes important as operation frequency increases. |
| Litz Wire |
| Wire consisting of a number of separately insulated strands that are woven or bunched together such that each strand tends to take all possible positions in the cross section of the wire as a whole. The current through each individual strand is divided equally since this wire design equalizes the flux linkages and reactance of the individual strands. In other words, a litz conductor has lower AC losses than comparable solid wire conductors which becomes important as the oeprating frequency increases (Also see Skin Effect). |
| LMDS |
| local multipoint distribution service |
| Load |
| Electronic components/circuits connected to the output pins of a converter. The characteristics (resistance, reactance, etc.) of the load determine the amount of power drawn from the converter |
| Load Decoupling |
| Placement of filter components (typically mF capacitors) at the power terminals of the load in order to reduce noise. |
| Load Loss |
| These losses are caused by the resistance of the windings under loaded conditions. |
| Load Regulation |
| Percentage change in output voltage caused by varying the output load over a specified range (with input line, temperature, etc. remaining constant). |
| Local Area Transport Area (LATA) |
| (1)A geographic area established for the provision and administration of communications service. It encompasses one or more designated exchanges, which are grouped to serve common social, economic and other purposes. (2) Contiguous local exchange areas that include every point served by a LEC within an existing community of interest and that serve as the dividing line for the allocation of assets and liabilities betweenthe IXC and the LEC. (3) A telephone company term that defines a geographic area", sometimes corresponds to an area code. |
| Local Loop |
| Refers to the physical copper pair or loop of wire from Central Office to the subscriber. |
| Local sensing |
| Using the output terminals of the converter to provide feedback to voltage regulation circuits. Also see Remote Sensing. |
| Logic Inhibit/Enable |
| Signal (typically TTL/CMOS compatible) used to turn a power supply output on/off. Also called Remote On/Off. |
| Long Term Stability |
| Change in output voltage of a converter over time with all other factors (line, load, temp. etc.) remaining constant. Expressed as a percent, the output change is primarily due to component aging. |
| Low Line |
| Minimum value of input line voltage speified for normal converter operation. |
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| Magnet Wire |
| Copper or aluminum wire with electrical insulating material applied to the surface to prevent continuity between adjacent turns in a winding. |
| Magnetic Energy |
| The product of the flux density (B) and the (de)magnetizing force (H) in a magnetic circuit required to reach that flux density. |
| Magnetic Flux |
| A contrived but not measurable concept that has evolved in an attempt to describe the ÒflowÓ of a magnetic field. Unlike electric current where there is an actual flow of electrons, a magnetic field is the result of the energy state of a series of magnetic domains. Conceptually, one could imagine that the sequential change of energy state as the result of an applied field represents ÒflowÓ. |
| Magnetic Lines Of Force |
| An imaginary line representing a magnetic field, which at every point has the direction of the magnetic flux at that point. |
| Magnetic Path |
| The route the magnetic flux ÒflowsÓ in a magnetic circuit. |
| Magnetic Path Length |
| The length of the closed path that magnetic flux follows around a magnetic circuit. AmpereÕs Law determines it. |
| Magnetic Wire |
| Wire used to create a magnetic field such as those in magnetic components (inductors and transformers). Magnet wire is nearly 100% copper and must be made from virgin copper. It is covered with a number of difference organic polymer film coatings. |
| Master/Slave Operation |
| Wire used to create a magnetic field such as those in magnetic components (inductors and transformers). Magnet wire is nearly 100% copper and must be made from virgin copper. It is covered with a number of difference organic polymer film coatings. |
| Maximum Ambient Operating Temperature |
| The highest ambient temperature at which a circuit is expected to operate. |
| Maximum Device Voltage |
| The highest voltage that can safely be dropped across a PolySwitch device in its tripped state under specified fault conditions. |
| Synonyms: Maximum Interrupt Voltage,Maximum Voltage,Vmax |
| Maximum Fault Current |
| The rated maximum value of peak pulse current of specified amplitude and wave shape that may be applied without damage. |
| Maximum Interrupt Current |
| The highest fault current that can safely be used to trip a PolySwitch device under specified conditions. Typically the lower the voltage dropped across the PolySwitch device in its tripped state, the higher the maximum interrupt current. Maximum interrupt currents are usually shown in this Databook at the maximum voltage. It may be possible to use a PolySwitch device at a higher interrupt current, but each such use must be individually qualified. |
| Synonyms: Imax |
| Maximum Interrupt Voltage |
| The highest voltage that can safely be dropped across a PolySwitch device in its tripped state under specified fault conditions. |
| Synonyms: Maximum Device Voltage,Maximum Voltage,Vmax |
| Maximum Load |
| Highest amount of output load allowable under the continuous operating specifications of a converter. |
| Maximum Operating Voltage |
| The maximum voltage across a PolySwitch device under a typical fault condition. In many circuits, this is the voltage of the power source in the circuit. It may be possible to use a PolySwitch device at a higher voltage, but each such use must be individually qualified. |
| Maximum Output Resistance |
| The resistance of a device at a specified voltage. |
| Maximum Power Dissipation |
| An inductor's ability to handle the heat generated by operating at maximum current at an ambient temperature, expressed in Watts (W) or milliwatts (mW). This is a function of the body area of the inductor, core material used, and varies for shielded vs. unshielded. |
| Maximum Resistance |
| The maximum resistance of a PolySwitch device at room temperature one hour after being tripped or after reflow soldering. |
| Synonyms: R1max |
| Maximum Switching Current |
| The maximum current that a device switches at safely without damage. |
| Maximum Voltage |
| The highest voltage that can safely be dropped across a PolySwitch device in its tripped state under specified fault conditions. |
| Synonyms: Maximum Device Voltage,Maximum Interrupt Voltage,Vmax |
| Maxwell |
| The unit of magnetic flux in the CGS system. One Maxwell = 10-8 webers. |
| MCNS |
| multimedia cable network system |
| Mean Time Between Failure (MTBF) |
| Unit of measure, expressed in hours, that gives the relative reliability of a converter. MTBF data is based upson actual operating data (demonstrated) or derived per the conditions of MIL-HDBK-217F (calculated). |
| Metropolitan Area Network (MAN) |
| A data communication network covering the geographic area of a city. Often used by a CAP to carry backbone traffic in their serving area. |
| Minimum Load |
| Minimum amount of output load required on a converter in order to maintain normal continuous operating specifications. Usually associated with PWM (Pulse Width Modulation) controlled converters. |
| Minimum Operating Temperature |
| Minimum ambient temperature at which a converter will start and operate within specifications. |
| MLT |
| The mean-length-turn of wire for a core. |
| MMDS |
| multi-channel, multipoint distribution service |
| Modulation |
| Process by which signal characteristics are transformed to represent information. Types of modulation include frequency modulation(FM), where signals of different frequencies represent different data values. |
| Module |
| Encapsulated DC-DC converter. |
| MOM |
| message-oriented middleware |
| MPEG |
| moving pictures experts group |
| MPLS |
| multi-protocol label switching |
| MPP Core(CoEv) |
| MPP is an acronym for molypermalloy powder. It is a magnetic material that has an inherent distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials such as ferrite. This characteristic allows a higher DC current level to flow through the inductor before is saturates. The basic raw materials are nickel, iron, and molybdenum. The ratios are approximately 80% nickel, 2-3% molybdenum, and 17-18% iron. The manufacturing process includes an annealing step as discussed in the Kool Mu¨ definition. MPP stores higher amounts of energy and has a higher permeability than Kool Mu¨. Cores are offered in 10 or more permeability selections. The core characteristics allow inductors to perform very well in switching power applications. Since the core can store higher energy, more DC current can be passed through the inductor before the core reaches saturation. However, the cost of MPP is significantly higher than Kool Mu¨, iron powder, and most ferrite. |
| MPP Core(Raychem) |
| MPP is an acronym for molypermalloy powder. It is a magnetic material that has an inherent distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials such as ferrites. This characeristic allows a higher DC current level to flow through the inductor before the inductor saturates.%0aThe basic raw materials are nickel, iron and molybdenum. The ratios are: approximately 80% nickel, 2% -3% molybdenum, and the remaining is iron. The manufacturing process includes an annealing step as discussed in the Kool Mu (r) definition. MPP stores higher amounts of energy and has a higher permeability than Kool Mu (r)%0aCores are offered in 10 or more permeability selections. The core characteristics allow inductors to perform very well in switching power applications. Since higher energy can be stored by the core, more DC current can be passed thorugh the inductor before the core saturates. The cost of MPP is significantly higher than Kool Mu (r) , powdered irons and most ferrite cores with similar sizes (See saturation current and Kool Mu (r)) |
| Multifilar Winding |
| A winding technique in which a single turn consists of two or more strands of magnetwire operating in parallel. This reduces some of the second order effects associated with a single strand of wire, including skin effect downfalls and winding ease. |
| Multiplexer(MUX) |
| A technique that enables several data streams to be sent over a single physical line. It is also a function by which one connection from a layer is used to support more than one connection to the next higher layer. (2) A device for combining several channels to be carried by one line or fiber. |
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| NAT |
| network address translation |
| NCC |
| network control center |
| NDIS |
| network drive interface specification |
| Network Interface Card (NIC) |
| The circuit board installed in a PC that provides the interface between a communicating PC and the network. |
| Network Management System (NMS) |
| A system responsible for managing at least part of a network. NMSs communicate with agents to help keep track of network statistics and resources. |
| No Load Loss (Core Losses) |
| These losses are caused by the magnetizing of the core and are always present. The way they are measured is by running full voltage with no load on the transformer |
| No Load Voltage |
| Voltage level present at the output pins of a converter when 0% load is applied. |
| NOC |
| network operations center |
| Noise |
| Unwanted electrical energy in a circuit that is unrelated t the desired signal. Sources of noise are most often generated by some type of switching circuit. Common sources include switching voltage regulators and clocked signals such as digital circuits. |
| Noise |
| Unwanted electrical energy in a circuit that is unrelated to the desired signal. Sources of noise are most often generated by some type of switching circuit such as switching voltage regulators and digital circuits. |
| Nominal Value |
| Ideal value that is used as a reference point. Typically, it is not the same as the value actually measured. |
| Nonlinear Material |
| Magnetic material that exhibits a permeability which changes dramatically when MMF is varied. |
| Normal Operating Current |
| The highest steady state current that is expected to flow in a circuit under normal operating conditions. At the maximum ambient operating temperature of the circuit, the hold current of a PolySwitch device used to protect the circuit is typically greater than the normal operating current. |
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| OEM |
| original equipment manufacturer |
| Oersted |
| The unit of magnetic field strength (H) in the CGS system. One Oersted equals the magnetomotive force of one Gilbert per centimeter of flux path. |
| Off-Line Power Supply |
| Power supply (linear or switching) that operates directly off the AC line. The input voltage is rectified and filtered prior to any isolation transformer. |
| Off-State Capacitance |
| Capacitance in the off-state measured at a specified frequency, amplitude, and DC bias. |
| Off-State Current |
| DC value of the current through a SiBar device that results from the application of the off-state voltage, VD. IDM designates the maximum off-state current. |
| Off-State Voltage |
| DC voltage when a SiBar device is in the off-state. VDM designates the maximum off-state voltage. |
| On-State Current |
| Current through a SiBar device in the on-state condition IT. |
| On-State Voltage |
| Voltage across a SiBar device in the on-state condition at a specified current, IT. |
| Open Circuit Inductance (LO) |
| The inductance measured at the winding of a transformer at a low flux density level. |
| Open Systems Interconnection(OSI) |
| A 7-layer architecture model for communications systems developed by ISO and used as a reference model for most network architectures. |
| Open-Circuit Voltage |
| See No Load Voltage. |
| Operating Range Current |
| The range of normal operating currents in a circuit containing a PolySwitch device. Typically the hold current of the PolySwitch device should be greater than the top of the operating current range. |
| Operating Temperature Range(CoEv) |
| Range of ambient temperatures over which a component can be operated safely. The operating temperature is different from the storage temperature in that it accounts for the componentÕs self-temperature rise caused by the winding loss. |
| Operating Temperature Range(Raychem) |
| Range of ambient temperatures over which a component can be operated safely. The operating temperature is different from the storage temperature in that it accounts for the component's self temperature rise caused by the winding loss from a given DC bias current. This power loss is referred to as the copper loss and is equal to: %0aPower Loss=(DCR)(1^2)dc%0aThis power loss results in an increase to the component temperature above the given ambient temperature. Thus, the maximum operating temperature will be less than the maximum storage temperature:%0aMaximum Operating Temperature = Storage Temperature - Self Temperature Rise |
| OSS |
| operational support system |
| Output Current Limiting |
| See Current Limiting and Foldback Current Limiting. |
| Output Filter |
| A low pass filter placed in the output of the rectified power converter to minimize (or smooth) the square wave or sine wave output of the converter. This filter has an LC,RC or Pi configuration. |
| Output Impedance |
| Ratio of change in output voltage to a change in output load current. Sometimes referred to as Dynamic Response. |
| Output Ripple and Noise |
| See Noise and Periodic and Random Distribution. |
| Output Voltage |
| Value of DC voltage measured at the output terminal of a converter. |
| Output Voltage Accuracy |
| Maximum allowable deviation of the DC output of a converter from its ideal or nominal value. Expressed as a percentage of output voltage. Often called output voltage tolerance |
| Output Voltage Range |
| Minimum and maximum output voltage limits within which a converter meets its operating specifications. |
| Overcurrent Protection |
| Output monitoring circuit activated if the converter exceeds a preset current level. |
| Overload Protection |
| See Current Limiting and Foldback Current Limiting. |
| Overshoot |
| Transient change in output voltage that exceeds specified accuracy limits. Typically occurs on converter turn on/off or with a step change in output load or input line. |
| Overtemperature Protection |
| Design feature that protects the silicon die from exceeding its designed operating temperature range. The device will thermally cycle until the abnormal condition is corrected. |
| Overvoltage Lockout |
| Design feature that protects the silicon die and downstream peripherals from supply voltage conditions that exceed its operating voltage limits. Raychem power switches have a nominal OVLO threshold of 6.4V. |
| Synonyms: OVLO |
| Overvoltage Protection (OVP) |
| Output monitoring circuit activated if a preset voltage level is exceeded. Depending on the type of circuit used, the OVP shuts the converter down, "crowbars" the faulty output or switches the converter to a different operating mode. |
| OVLO |
| Design feature that protects the silicon die and downstream peripherals from supply voltage conditions that exceed its operating voltage limits. Raychem power switches have a nominal OVLO threshold of 6.4V. |
| OXC |
| optical cross-connect |
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| Packet |
| (1)A logical grouping of information that includes a header and (usually) user data. (2) Continuous sequence of binary digits of information is switched through the network and an integral unit. |
| Packet Switched Network |
| A network in which data is transmitted in units called packets. The packets can be routed individually over the best available network connection and reassembled to form a complete message at the destination. |
| Pair Gain |
| The multiplexing of x phone conversations over a lesser number of physical capabilities. "Pair gain" is the number of conversations obtained, divided by the number of wire pairs used by the systems. |
| PAN |
| personal area network |
| Parallel Operation |
| Operating Mode in which two or more power supplies are connected in parallel. The output currents are summed together into a single load, providing a higher level of output power than that available from a single DC-DC. Parallel operation requires DC-DCs speed specifically designed to share loads. Also see Master-Slave Operation. |
| Passive Aging Test |
| A test described in RaychemÕs PS300 publication in which the resistance of a PolySwitch device at room temperature is measured before and after aging at an elevated temperature (e.g., 70¡C or 85¡C) for an extended time (e.g., 1000 hours). |
| Pd |
| The power (in watts) dissipated by a PolySwitch device in its tripped state. The power dissipation is the product of the current flowing through the device and the voltage across the device, in the tripped state. |
| Peak On-state Surge Current |
| Current through the device in the on-state condition. |
| Peak Pulse Current |
| Rated maximum value of peak pulse current of specified amplitude and waveshape. |
| Percent Ripple |
| The percentage of ripple or AC flux to total flux, or in an inductor, the percentage of alternating current to average current. |
| Percent Saturation |
| The 100% permeability minus the percent of initial permeability. ie 20% saturation = 80% of initial permeability. |
| Periodic and Random Deviation (PARD) |
| Noise and ripple voltage superimposed on a converter's DC output. Typically specified at full load, it is expressed in peak-to-peak or RMS volts over a given bandwidth. |
| Permanent Virtual Circuit (PVC) |
| A defined virtual link with fixed end-points that are set-up by the network manager. A single virtual path may support multiple PVCs. |
| Permeability |
| The ratio of the changes in flux density to changes in the magnetizing force. The permeability of a magnetic material is the characteristic that gives the core the ability to concentrate lines of magnetic flux. The core material, as well as the core geometry, affects the coreÕs effective permeability. For a given core shape, size, and winding, higher permeability materials result in higher inductance values as opposed to lower permeability materials. |
| Permeability (Core) |
| The permeability of a magnetic core is the characteristic that gives the core the ability to concentrate lines of magnetic flux. The core material, as well as the core geometry, affect the core's effective permeability. For a given core shape, size and material, and a given winding, higher permeability magnetic materials result in a higher inductance values as opposed to lower permeability materials. |
| Pi-Filter |
| A filter consisting of two capacitors connected in parallel with a series inductor. These fileters arc commoonly found near DC-DC converters to filter ripple curent and voltage. |
| Polarity |
| Ability of a converter to produce an output that is positive or negative referenced to ground. Also see Floating Output. |
| Positive Temperature Coefficient |
| A term used to describe a material whose resistivity increases as temperature increases. PolySwitch devices make use of conductive polymers that show nonlinear PTC behavior. |
| Synonyms: PTC |
| Post Regulation |
| Output circuit that uses a linear regulator to prove line/load regulation and reduce ripple and noise. In PWM controlled converters, post regulation adds expense and degrades converter supply efficiency. |
| Post-Reflow Resistance |
| The resistance of a PolySwitch device at room temperature one hour after it has been connected to a circuit board by reflow soldering under specified conditions. |
| Post-Trip Resistance |
| The resistance of a PolySwitch device at room temperature one hour after the device has been tripped for the first time, under specified conditions. |
| Postal, Telegraph and Telephone Company (PTT)" |
| Generic term for a provider of these services. A governmental agency in many countries. |
| POTS |
| Plain Old Telephone Service |
| Powdered Iron Core |
| Powdered iron is a magnetic material that has an inherent distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials such as ferrites. This characteristic allows a higher DC current level to flow through the inductor before the inductor saturates.%0aPowdered iron cores are made of nearly 100% iron. The iron particles are insulated form each other, mixed with a binder (such as phenolic or epoxy) and pressed into the final core shape. The cores are cured via a baking process. Other characteristics of powerdered iron cores include: they are typically the lowest cost alternative and their permeabilities typically have a more stable temperature coefficient than ferrites (Also see Saturation Current) |
| Power Density |
| Ratio of converter output power to converter volume. |
| Power Dissipation |
| The power (in watts) dissipated by a PolySwitch device in its tripped state. The power dissipation is the product of the current flowing through the device and the voltage across the device, in the tripped state. |
| Synonyms: Pd |
| Power Factor Correction |
| Design technique usually applied ot the input of off-line converters that improves the converter;s power factor and minimizes harmonics generated by the converter onto the AC power line. |
| Power Good |
| Signal (typically a visible LED) that indicates the DC output of the primary channel of a converter is still present. |
| Power Loss Density (mW/cm3) |
| The power absorbed by a body of ferromagnetic material and dissipated as heat. |
| Power MOSFET |
| Semiconductor device used as a power switch in converters. |
| Power Rating |
| Specified power available at the converter output pins. |
| Power Switch |
| MOSFET-based switch that controls the flow of power through its output using an enable (EN) signal from a system controller. Advanced designs will include integrated pull-up resistors and capacitors to minimize board space and cost. |
| Power Transformer |
| Magnetic-core transformer for operation at 60 hertz, with nearly zero source impedance, to transfer power from line voltage to some required voltage. |
| Primary Circuits |
| Input side of an isolated. |
| Primary Current |
| Input side of an isolated DC-DC converter. See Secondary Circuit. |
| Primary Winding(CoEv) |
| The winding in a transformer that supplies the exciting MMF to the core. |
| Primary Winding(Raychem) |
| The winding connected to the source of energy. |
| PTC |
| A term used to describe a material whose resistivity increases as temperature increases. PolySwitch devices make use of conductive polymers that show nonlinear PTC behavior. |
| Pulse Transformers |
| Transformers designed for excitation that consists of short duration pulses repeated at a specific rate. |
| Pulse Width Modulation (PWM) |
| Circuit used in converters to regulate output voltage. Regulation is achived by varying the conduction time of the transistor switches. |
| Pure Inductors |
| Used at all frequencies to provide an electronic circuit with inductive reactance. |
| Push-Pull |
| A switching power supply topology where power is delivered to the load during the whole input cycle. These can achieve power levels in excess of 1000VA. Push-pull transformers are practical at low input voltages and higher output power. They are not advisable for off line converters because the power switches operate at collector stress voltages of twice the supply voltage. |
| Push-Pull Converter |
| Converter topology usually configured as a forward converter, but uses two transistor switches and a center tapped transformer. The transistor switches turn on and off alternately. Also see Boost Regulator, Buck Regulator, Bridge Converter, Flyback Converter and Resonant Converter. |
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| Q |
| The Q value of an inductor is a measure of the reative losses in a inductor. The Q is also known as the quality factor and is techncially defined as the ratio of inductive reactance to effective resistance and is represented by:%0aQ |
| Q (Q Factor) |
| A measure of the relative losses in an inductor. It is also known as the quality factor, defined as the ratio of inductive reactance to effective resistance. Q is zero at the SRF of an inductor. |
| QAM |
| Quadrature Amplitude Modulation. A two-dimensional modulation used for ADSL, cable modems and proposed for VDSL. CAP is a special case of QAM. In QAM, a single carrier frequency is modulated in both sine and cosine components. |
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| R1max |
| The maximum resistance of a PolySwitch device at room temperature one hour after being tripped or after reflow soldering. |
| Synonyms: Maximum Resistance |
| Ra max |
| Maximum functional resistance of device before and after defined stress tests. |
| Ra min |
| Minimum functional resistance of device before and after defined stress tests. |
| RADSL |
| Rate-Adaptive Digital Subscriber Line. A simple extension of ADSL to encompass a wide variety of data rates depending on the line's transmission capability. RADSL can either CAP or DMT ADSL. |
| Rated Current |
| The level of continuous DC current that can be passed through the inductor. This DC current level is based on a maximum temperature rise of the inductor at the maximum rated ambient temperature. The rated current is related to the inductor's ability to minimize the power losses in the winding by having a low DC resistance. It is also related to the inductor's ability to dissipate this power loss in the windings. Thus, the rated current can be increased by reducing the DC resistance or increasing the inductor size.%0aFor low frequency current waveforms the RMS current can be substituted for the DC rated current. The rated current is not related to the magnetic properties of the inductor (Also see Incremental Current and Saturation Current) |
| Reactance |
| The imaginary part of the impedance (Also see Impedance) |
| Rectification |
| The process of using a diode to convert and AC voltage into DC. There are two general types of retificitaion processes, half-wave and full-wave. |
| Rectifier |
| Device that allows current to flow in only one direction, such as a diode. |
| Reduntant Operation |
| Parallel configuration of converters used in distributed power system to increase system reliabiltiy. Converters may be used in a "N+1" architucture. |
| Reflected Ripple Current |
| See Input Reflected Ripple Current. |
| Regional Bell Operating Companies (RBOC) |
| Seven LEC telephone companies created after AT&T divestiture. |
| Regulation |
| Ability of a converter to maintain an output voltge to within specified limits under varying conditions of input line and output load. Also see Linear Regulation. |
| Remote LAN Access |
| A data communications such as a corporate or campus environment in which the computer networks can be accessed remotely via public telecommunications networks. |
| Remote Sensing |
| Using sense leads connected at the output load provides feedback to voltage regulation circuits of a converter. This arrangement is used to compenate for voltage losses from long leads to a load. Also see Local Sensing. |
| Remote Shutdown |
| See Logic Inhibit/Enable. |
| Repeater |
| An electronic device used to regenerate digital signals and restore signal and restore signal quality across a certain distance of cable. |
| Residual Flux |
| The flux that remains in a core when the applied MMF is returned to zero. |
| Resistance |
| The resistance of a PolySwitch device under specified conditions (e.g., 20¡C), before connection into a circuit. Devices of a particular type will be delivered with a range of resistances; therefore, a minimum value, Rmin, and/or a maximum value, Rmax, are often given. |
| Synonyms: Initial Resistance,Base Resistance,Rmin,or Rmax |
| Resistance Binned Devices |
| Resistance binned devices are supplied such that all parts in one package are within 0.5 ? of each other. Individual binned packages are supplied from the full resistance limits of the specified product. |
| Resistance Sorted Devices |
| Resistance sorted devices (part number suffix ÒRxÓ) are supplied with resistance values that are within specified limits of the productÕs full range of resistance. |
| Resistance, Maximum |
| The maximum resistance of a PolySwitch device at room temperature one hour after being tripped or after reflow soldering. |
| Synonyms: R1max |
| Resistance, Post-Reflow |
| The resistance of a PolySwitch device at room temperature one hour after it has been connected to a circuit board by reflow soldering under specified conditions. |
| Resistance, Post-Trip |
| The resistance of a PolySwitch device at room temperature one hour after the device has been tripped for the first time, under specified conditions. |
| Resonant Converter |
| Switching converter technology in which a resonant tank circuit operating at very high frequencies is used to transfer energy to the output. |
| Return |
| Common terminal on the output of a DC-DC converter. It is the return current path for the output. Also see Common. |
| Reverse Current |
| See Leakage Current. |
| Reverse Voltage Protection |
| Converter feature that prevents damage to internal components if a reverse voltage is inadvertently applied to the input or ouput terminals. |
| Reversible Temperature Coefficient |
| Changes in flux which occurs with temperature change. They are spontaneously regained when the temperature is returned to its original point. There are two values reported: reversible temperature coefficients of inductance (Br) and Coercivity (Hci). The temperature range over which they have been measured and specified should be stated. Most materials exhibit a non-linear response with temperature. |
| RFI(CoEv) |
| An acronym for radio frequency interference. It is an older and more restrictive term that is used interchangeably with EMI. |
| RFI(Raychem) |
| RFI is an acronym for Radio-Frequency Interference. It is an older and more restrictive term that is used interchangeably with EMI (Also see EMI.) |
| Ripple and Noise |
| See Periodic and Random Deviation (PARD) |
| Ripple Voltage |
| The periodic alternating voltage imposed on the voltage output of a switching voltage converter. The ripple voltage is normally specified as a peak-to-peak value. |
| Rmax |
| The resistance of a PolySwitch device under specified conditions (e.g., 20¡C), before connection into a circuit. Devices of a particular type will be delivered with a range of resistances; therefore, a minimum value, Rmin, and/or a maximum value, Rmax, are often given. |
| Synonyms: Initial Resistance,Base Resistance,Rmin,or Resistance |
| Rmin |
| The resistance of a PolySwitch device under specified conditions (e.g., 20¡C), before connection into a circuit. Devices of a particular type will be delivered with a range of resistances; therefore, a minimum value, Rmin, and/or a maximum value, Rmax, are often given. |
| Synonyms: Initial Resistance,Base Resistance,Resistance,or Rmax |
| Royer Converter |
| Self-oscillating, push-pull switching circuit configuration commonly used in low cost, low power DC-DC converters. Also called the classical converter. |
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| S-HDSL |
| Single pair transmission using HDSL technology, normally 2B1Q. |
| Saturable Reactor |
| Describes the main element of a magnetic amplifier used to control electrical power such as for electrical resistance element heating of furnaces. |
| Saturation Current(CoEv) |
| The DC bias current flowing through an inductor which causes the inductance to drop by a specified amount from the initial zero DC bias inductance value. Common specified inductance drop percentages include 10% for ferrite cores and 20% for iron powder cores in energy storage applications. |
| Saturation Current(Raychem) |
| The DC bias current flowing through tile inductor which causes the inductance to drop by a specified amount form the initial zero DC bias inductance value. Common specified inductance drop percentages include 1-% and 20%. IT is useful to use the 10% inductance drop value for ferrite cores and 20% for powdered iron cores in energy storage applications.%0aThe cause of the inductance to drop due to the DC bias current is related to the magnetic properties of the core. The core, and some of the space around the core, can only store a given amount of magnetic ~ density. Beyond the maximum flux density point, the permeabilty of the core is reduced. Thus, the inductance is caused to drop. Core saturation does not apply to air-core inductors (Also see Incremental Current and Permeability) |
| Saturation Flux Density |
| The flux density value at which a given material saturates. |
| Saturation(CoEv) |
| Exists when an increase in magnetizing force (H) does not cause a corresponding increase in the flux density (B) of the material. The cause of saturation is relative to the magnetic properties of the core. Each material can store only a given amount of magnetic flux density. Beyond this the permeability of the core is reduced dramatically causing inductance to fall. |
| Saturation(Raychem) |
| Maximum density of magnetic flux that can be present in a magnetic material |
| SDH |
| synchronous digital hierarchy |
| SDSL |
| Symmetric Digital Subscriber Line. |
| Secondary Circuit |
| Output side of an isolated DC-DC converter. Also see Primary Circuit. |
| Secondary Winding(CoEv) |
| The winding in a transformer that supplies the load with electrical energy which has been converted from the induced magnetic energy in the core. |
| Secondary Winding(Raychem) |
| The winding is the coil where energy is induced from the primary. |
| Self Resonant Frequency (SRF) |
| The frequency at which an inductorÕs distributed capacitance resonates with the inductance. The inductive reactance and the capacitive reactance are equal. The inductor acts as a pure resistance. The Q of an inductor is equal to zero at the SRF. |
| Self-Inductance |
| Another way of saying inductance. |
| Self-Powered Hub |
| Class of devices that derive power from its own source. Examples include monitors and self-powered USB hubs. |
| Sendust |
| A 9% silicon, 6% aluminum, and 85% iron alloy in particulate form. The particles are coated with a dielectric film, compacted, and cured to form magnetic parts such as inductor cores. |
| Sense Line |
| Output line used in a remote sensing connection to route the output voltage (at the load) back to the control feedback loop. Also see Remote Sensing. |
| Series Operation |
| Master-slave configuration in which two or more isolated converters are connected to obtain a hgher output voltage level (converter inputs connected in parallel) or wider input voltage range (converter inputs connected in series) than that obtainable from one module. Also see Master-Slave Operation. |
| Series Regulator |
| Linear regultor (internal or external to the converter)placed in a series with the load to ahcieve a constant voltage across the load. This is the most popular method of linear regulation. Also see Linear Regulation, Post Regulation and Shunt Regulator. |
| Set Up Transformer |
| When the secondary is at a higher voltage than |
| Shielded Inductor |
| An inductor designed for its core to contain a majority of its magnetic field. Some inductor designs are self shielding. Examples of these are magnetic core shapes which include toroids, pot cores and B-Cores. Magnetic core shapes such as slug cores and bobbins require the application of a magnetic sleeve or similar method to yield a shielded inductor.%0aIt should be noted that magnetic shielding is a matter of degree. A certian percentage of the magnetic field will escape the core material. This is even applicable to toroidal cores as lower core permeabilities will have higher fringing field than will high permeability toroidal cores (Also see Closed Magnetic Path.) |
| Shielded Inductor |
| An inductor designed for its core to contain a majority of its magnetic field. Some inductor designs are self-shielding, such as toroids and pot cores. |
| Shielding |
| A method of blocking electromagnetic interference to protect sensitive devices. In an inductor this is placed in the form of a thin metal sheet, a winding, or the core itself can act as a shield. |
| Short Circuit Protection |
| See Current Limit and Foldback Current Limit. |
| Shunt Regulator |
| Linear regulator (internal or external to the converter) placed in parallel with the load to achieve a constant voltage across the load. Also see Linear Regulation, Post Regulation and Series Regulator. |
| Simple Network Management Protocol (SNMP) |
| A network management standard initially established to allow multi-vendor networking devices to be managed more easily with common management tools. |
| Simple Winding |
| A winding for a toroidal core which results in 78% of the cores inside diameter remaining. Often times this will produce a single layer winding. |
| Single Layer Winding |
| A winding for a toroidal core which will result in the full utilization of the inside circumference of the core without overlapping of turns. The thickness of the wire and tightness of the winding will affect results. |
| Sintered Iron |
| Powdered iron that has been pressed and sintered into a structural form. This type of material occasionally is used in a magnetic application, but they normally exhibit excessive core losses. |
| Six-Sided Shielding |
| Converter packaging technique in which the unit is placed into a metal case. Theis metal shielding minimized any noise radiation from the converter components. A continous shielded case has the base (or header) welded on, further reducing potential noise leakage. |
| Skewing Of The Loop |
| When an air gap is added to a magnetic path, the hysteresis loop is made to lean over (permeability is reduced). It is said to be skewed or sheared. |
| Skin Effect(CoEv) |
| The tendency of an alternating current to flow near the surface of a conductor rather than utilizing the entire cross-sectional area. The phenomenon causes the resistance of the conductor to increase with an increase in frequency. The magnetic field associated with the current in the conductor causes eddy currents near the center of the conductor, which opposes the flow of the main current near the center of the conductor. The main current is forced further to the surface as the frequency is increased. |
| Skin Effect(Raychem) |
| Skin effect is the tendency for alternating current to flow near the surface of the conductor in lieu of flowing in a manner as to utilzie the entire cross-sectional area of tile conductor. Ths phenomenon causes the resistance of the conductor to increase. The magnetic field associated with the current in teh conductor causes eddy currents near the center of the conductor which opposes the flow of the main current flow near the center of the conductor. The main current flow is forced further to the surface as the frequency of the alternating current increasing (Also see Litz Wire.) |
| Slug Core |
| A core shaped like a rod, with the winding(s) placed around the diameter. |
| Soft Magnetic Material |
| A ferromagnetic material that is easily magnetized and demagnetized. |
| Soft Start |
| Converter input circuit that limits the inrush of current at turn on. |
| SOHO |
| small office/home office |
| Solvent Resistance Test |
| A test described in RaychemÕs PS300 publication to test the durability of the markings on PolySwitch devices when exposed to various solvents. |
| SONET |
| Synchronous Optical Network- A recently emerging networking standard that utilizes fiber optics to create backbone networks, capable of transmitting at extremely high speeds and accommodating gigabit-level bandwidth. |
| Sorted |
| Binned refers to resistance-matched devices, which are supplied such that all parts in one particular package (or reel) are within 0.5 ohms of each other (1.0 ohms for TR250-080T devices). Individual matched packages are supplied from the full resistance range of the specified device. The benefit is that resistance-matched devices reduce the tip-ring resistance differential, reducing the possibility of line imbalance. Sorted devices are those that are supplied with resistance values that are within specified segments of the device's full range of resistance, giving greater design flexibility. |
| Synonyms: Binned |
| Source |
| Power bus that drives the DC-DC converter. Also see Bus. |
| Spanning Tree |
| An algorithm, the original version of which was invented by Digital Equipment Corporation used to prevent bridging loops by creating a spanning tree. The algorithm is now documented in the IEEE 802.1d specification, although the Digital algorithm and the IEEE 802.1d algorithm are not the same, nor are they compatible. |
| Square Wave |
| An excitation that consists of an abrupt on/off cycling of the voltage. This typically goes in both the positive and negative direction. A positive-only square wave would be typical of pulse excitation. |
| Squareness Ratio |
| The ratio of residual flux density to the maximum (saturation) flux density. |
| SRF (Self Resonant Frequency) |
| The frequency at which tile inductor;s distributed capacitance resonates with the inductance. It is at this frequency that the inductance is equal to the capacitance and they cancel each other. The inductor will act purely resistive with a high impedance at the SRF point. The distributed capacitance is caused by the turns of ~re layered on top of each other and around the core. This capacitance is in parallel to the inductance. At frequencies above the SRF, the capacitive reactance of the parallel combination will become the dominant component.%0aAlso, tile Q of the inductor is equal to zero at the SRF point since the inductive reactance is zero. The SRF is specified in Mhz and is listed as a minimum value on product data sheets (Also see Distributed Capacitance) |
| Stability |
| See Long Term Stability. |
| Standby Current |
| Current drawn by a converter when it has no load and has been shut down by a logical inhibit signal. |
| Step Change |
| Sudden change in a converter parameter. Typically used in referring to changes in output load or input line during converter testing. |
| Step Down Transformer |
| When the secondary has a lower voltage than the primary. |
| Storage Temperature Range(CoEv) |
| Range of ambient temperatures over which a component can be stored safely. See operating temperature range. |
| Storage Temperature Range(Raychem) |
| Range of ambient temperatures over which a component can be stored safely (Also see Operating Temperature Range) |
| Supply Current |
| Rated output current of a given device. Power switch devices have been designed to support a continuous load (supply) current of 0.6A at ambient temperature. |
| Supply Voltage |
| Voltage level of the power switch input. Raychem power switch devices have been designed to operate using supply voltage levels from 3.0V to 5.5V. |
| Surface Area |
| The effective surface area of a typical wound core available to dissipate heat. |
| Swing |
| A term used to describe how inductance responds to changes in current, ie a 2:1 swing corresponds to an inductor which exhibits two times more inductance at very low current than it does at its maximum rated current. This would also correspond to the core operating at 50% of initial permeability (50% saturation). |
| Swinging Inductors |
| A special type of inductor that exhibits high inductance at low MMF and moderate inductance at high MMF. There are two popular techniques for accomplishing this: placing a common winding on a high permeability core and a low permeability core, and placing a staggered gap into a high permeability core. |
| Switch Mode Power Supply |
| A power conversion technique that involves breaking the input power into pulses at a high frequency by switching it on and off and re-combining these pulses at the output stage. Using this technique, an unregulated input voltage can be converted to one or more regulated output voltages at relatively high efficiencies. |
| Switched Virtual Circuit (SVC) |
| A virtual link, with variable end-points, established through an ATM network. With an SVC, the user defines the end-points when the call is initiated that are subsequently terminated at the end of the call. With a Permanent Virtual Circuit(PVC), the end-points are predefined by the network manager. A single virtual path may support multiple. |
| Switching Frequency |
| The rate at which the DC input to a switching regulator is switched on and off. |
| Switching Regulator(CoEv) |
| A circuit that is designed to regulate the output voltage from a given unregulated input voltage by using a closed control loop design. The most common switching regulator types involve a magnetic component, such as an inductor or transformer, that is used to store and transfer energy to the output by having the current switched on and off. |
| Switching Regulator(Raychem) |
| A circuit that is designed to regulate the output voltage, from a given input voltage, by using a closed control loop design. The most common switching regulator types involve a magnetic component, such as an inductor or transformer, that is used to store and transfer energy to the output by having the current switched on and off (Also see Boost Regulator and Buck Regulator) |
| Symmetrical Transmission |
| Transmission in which a channel sends and receives data with the same signaling rate. |
| System Damage Voltage |
| Maximum voltage across a SiBar device at breakdown measured under a specified voltage rate of rise and current rate of rise. |
| Synonyms: Breakover Voltage |
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| T1 |
| Digital transmission facility operating with a nominal bandwidth of 1.544 Mbps. Also known as Digital Signal Level 1 (D1). Composed of 24 DS-0 channels in many cases. The T1 digital transmission system if the primary digital communication system in North America. |
| T3 |
| Digital transmision facility operating at 45 Mbps bandwidth. Composed of 28 DS-1 channels in many cases. Also known as DS-3. |
| Tape Wound Core(Raychem) |
| Cores made by rolling strips of alloy iron into a toroidal shape. The metal strips have a precisely controlled thickness which are coted with a very thin insulation material to prevent the metal in the layers to make contact with each other. The finished cores have an outside coating to protect the metal layers and they are offered in a variety of material mixes. Tape wound cores are capable of storing high amounts of energy and contain a high permeability. Their major disadvantage is that they are relatively expensive when compared to other core types (Also see Toroidal Inductor) |
| Tape Wound Cores(CoEv) |
| Cores made by rolling strips of alloy iron into a toroidal shape. The metal strips have a precisely controlled thickness, which are coated with a very thin insulating material to prevent the metal in the layers to make contact with each other. The finished cores have an outside coating to protect the metal layers and they are offered in a variety of material mixes. Tape wound cores are capable of storing high amounts of energy and contain a high permeability. Their major disadvantage is that they are relatively expensive when compared to other core types. |
| TDM |
| time division multiplexing |
| TDMA |
| time division multiple access |
| Technischer Uberwachungs-Verin (TUV) |
| Organization approved for testing products to VDE standards. US-based companies often use TUV in place of VDE because they hae established facilities in the US. |
| Telecommunications Transformers |
| Also referred to as broadband transformers, these are transformers specialized for connecting a piece of equipment to the phone line or telephone network. Its function is to isolate the equipment from the phone line, improve common mode noise rejection, and match different impedances. |
| Telecommuter |
| Person who performs work at home while linked to the office by means of a telecommunications-equipped computer system. |
| Temperature Coefficient (TC) |
| The relative change of the quantity considered divided by the temperatures producing it. |
| Temperature Coefficient Of Inductance |
| (Tc of L)Is the value of inductance change as a function of temperature exposure, normally expressed in parts per million per degrees Celsius. This is a calculation comparing inductance at a reference temperature (25 degrees C, room ambient) to the extremes and other temperatures within operating range. Can be called Percent Delta L. or Temperature Stability: the lower the change the better for most applications. |
| Temperature Factor (TF) |
| The fractional change in initial permeability over a temperature range divided by the initial permeability. |
| Temperature Range |
| The ambient temperature range of the air (or other medium) surrounding a PolySwitch device under normal operating conditions. |
| Temperature Rise |
| The increase in surface temperature of a component in air due to the power dissipation in the component. The power dissipation for an inductor includes both copper and core losses. |
| Temperature, Maximum Ambient Operating |
| The highest ambient temperature at which a circuit is expected to operate. |
| Termal Conductivity |
| Given materials ability to conduct heat, which is the time rate for heat transfer (via conduction) across a unit material thickness of 1 meter and when the temperature differential of the two opposite faces is 1 degree K. |
| Tesla |
| The MKSA (SI) unit for magnetic flux density, defined by FaradayÕs Law. A Tesla represents a volt-second per square meter per turn. One Tesla is equal to 10,000 Gauss. |
| Test Frequency |
| Is the industry/military standard for testing a range of inductances. It is not intended as the application frequency. Expressed in megahertz (MHz) or kilohertz (KHz) |
| Test, Humidity Aging |
| A test described in RaychemÕs PS300 publication in which the resistance of a PolySwitch device at room temperature is measured before and after aging at an elevated temperature (e.g., 40¡C) and high humidity (e.g., 95% RH) for an extended time (e.g., 1000 hours). |
| Test, Passive Aging |
| A test described in RaychemÕs PS300 publication in which the resistance of a PolySwitch device at room temperature is measured before and after aging at an elevated temperature (e.g., 70¡C or 85¡C) for an extended time (e.g., 1000 hours). |
| Test, Solvent Resistance |
| A test described in RaychemÕs PS300 publication to test the durability of the markings on PolySwitch devices when exposed to various solvents. |
| Test, Thermal Shock |
| A test in which the resistance of a PolySwitch device at room temperature is measured before and after a temperature cycling treatment (e.g., cycled 10 times between Ð55¡C and +125¡C). |
| Thermal Conductivity |
| Given materials ability to conduct heat, which is the time rate for heat transfer (via conduction) across a unit material thickness of 1 meter and when the temperature differential of the two opposite faces is 1 degree K. |
| Thermal Derating |
| The change in the hold current and trip current of a PolySwitch device that takes place as there is a change in the ambient temperature of the air (or other medium) surrounding the device. An increase in ambient temperature decreases the hold current (and the trip current). A decrease in ambient temperature increases the trip current (and the hold current). |
| Thermal Gasket |
| Flexible pad or wafer with a very low thermal resistance that is put between a power module baseplate and heat sink to ensure high thermal conductivity across the junction |
| Thermal Joint Compound |
| A fluid or paste spread between the mating surfaces of a power device baseplate and a heat sink or system chassis. |
| Thermal Protection |
| Feature that shuts the converter down if the internal tempurature exceeds preset limits. Also called thermal shutdown. |
| Thermal Resistance |
| Measure of a given material;s opposition to the flow of heat. Units are in degrees C/W. |
| Thermal Resistivity |
| Measure of a material;s ability to impede the flow of heat. Typically given in degrees C T/W, where T is the material thickness and W is the power flowing through the material in watts. |
| Thermal Shock Test |
| A test in which the resistance of a PolySwitch device at room temperature is measured before and after a temperature cycling treatment (e.g., cycled 10 times between Ð55¡C and +125¡C). |
| Three-Terminal Regulator |
| Regulator packaged in a standard 3-terminal transistor package. These devices can be a switching type or a linear shunt or series regulator. |
| Time-to-Trip |
| The time needed, from the onset of a fault current, to trip a PolySwitch device. For any particular type of PolySwitch device, trip time depends upon the size of the fault current and the ambient temperature. The higher the fault current and/or the higher the temperature, the shorter the trip time. |
| Synonyms: Trip Time,TtT |
| Toroid |
| A core that has a donut shaped surface. Toroidal cores are available in many magnetic core materials. Characteristics of toroidal inductors include self-shielding due to a closed magnetic path, efficient energy transfer, high coupling between windings, and early saturation. |
| Toroidal Inductor |
| An inductor constructed by placing a winding(s) on a core that has a donut shaped surface. Toroidal cores are available in many magnetic core materials within the four basic types: Ferrite, Powdered iron, Alloy and High Flux, and Tape Wound. Characteristics of toroidal inductors include: self shielding (closed magnetic path), efficient energy transfer, high coupling between windings and early saturation. |
| Tracking |
| For a multiple output converter the parameter that gives the change in one output voltage caused by a change in the voltage level or load on another output. |
| Transformer |
| A passive device that changes voltage, current, or impedance to the required parameters. This is usually done by placing two or more windings around a soft magnetic core. Applying a voltage to the primary winding will produce a magnetic field in the core, and in turn induce a voltage in the secondary winding(s). |
| Transient |
| Spike or step change in a converter paramenter. Commonly used in describing input line and output load characteristics. |
| Transient Recovery Time |
| Time required for a converter output to return to within specified limits following a step change in output load current. Expressed as a percentage of rated value. |
| Transient Suppression |
| The use of special devices to minimize the effects of transients in electronic circuits. Transient suppression devices include the metal oxide varistor (MOV), semiconductor transient voltage suppressor (TVS) and gas tube. |
| Transmission Controal Protocol/Internet Protocol (TCP/IP) |
| A reliable, full duplex, connection-oriented end to end transport protocol running on top of IP. |
| Transparent LAN Service |
| Service offered by a provider that is used to connect LANs at geographically separated sites. "Transparent" means the connection is invisible to the user and typically runs at the same speed as the LANs. |
| TRI |
| telephony return interface |
| Trip |
| Switching of a PolySwitch device from a low resistance to a high resistance. In its low-resistance state, the device permits normal currents to flow in a circuit. Occurrence of a fault drives the device to its high-resistance (or ÒtrippedÓ) state, and this reduces the current in the circuit to a low level. |
| Trip Current |
| The smallest steady state current that, if passed through a PolySwitch device, will cause the device to trip, under specified conditions. |
| Synonyms: IT |
| Trip Cycle |
| The tripping and resetting of a PolySwitch device under specified conditions. |
| Trip Cycle Life |
| The number of trip cycles that a PolySwitch device will undergo without failure, with failure being defined in a specified way. |
| Trip Time |
| The time needed, from the onset of a fault current, to trip a PolySwitch device. For any particular type of PolySwitch device, trip time depends upon the size of the fault current and the ambient temperature. The higher the fault current and/or the higher the temperature, the shorter the trip time. |
| Synonyms: Time-to-Trip,TtT |
| TtT |
| The time needed, from the onset of a fault current, to trip a PolySwitch device. For any particular type of PolySwitch device, trip time depends upon the size of the fault current and the ambient temperature. The higher the fault current and/or the higher the temperature, the shorter the trip time. |
| Synonyms: Time-to-Trip,Trip Time |
| Turn Ratio |
| The ratio of the primary voltage (or turns) to the secondary voltage (or turns) |
| Twisted Pair |
| Cable consisting of two 18 to 24 AWG (American Wire Gauge) solid copper strands twisted around each other. The twisting provides a measure of protection from electromagnetic and radio-frequency interference. |
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| UDP |
| user datagram protocol |
| UMTS |
| universal mobile telecommunications service |
| Undershoot |
| Transient change in a converter output voltage that does not meet the lower limit of the voltage accuracy specificiation. Typically occurs at converter turn on/off or with some step change in output load or input line. Also see Voltage Accuracy. |
| Undervoltage lockout |
| Design feature that helps regulate the quality of the output voltage by turning the device OFF in response to supply voltages that fall below its UVLO level. Raychem power switches have a nominal UVLO threshold of 2.5V. |
| Synonyms: UVLO |
| Underwriters Laboratory (UL) |
| Independent organization that conducts safety testing of products to established standards. |
| Uninterruptible Power Supply (UPS) |
| Power supply that will continue to operate after the loss of AC input power. |
| USB |
| Universal Serial Bus interoperability standard that defines the electrical power and signal transfer requirements in computing and multi-media applications. USB power requirements define a supply and output voltage of 5V, with output currents rated at 0.5A for self-powered equipment and 0.1A output for bus-powered equipment. |
| UVLO |
| Design feature that helps regulate the quality of the output voltage by turning the device OFF in response to supply voltages that fall below its UVLO level. Raychem power switches have a nominal UVLO threshold of 2.5V. |
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| VDSL |
| very high bit-rate subscriber line |
| Verband Deutscher Elektrontechniker (VDE) |
| German organization that sets standards for product safety and noise emissions and test and certifies products to those standards. |
| Vmax |
| The highest voltage that can safely be dropped across a PolySwitch device in its tripped state under specified fault conditions. |
| Synonyms: Maximum Device Voltage,Maximum Interrupt Voltage,Maximum Voltage |
| VoDSL |
| voice over digital subscriber line |
| VoIP |
| Voice over Internet protocol |
| Volt Microsecond Constant |
| The product of the voltage applied across the winding and the time for the magnetizing current to reach 1.5 times the linear extrapolation of the current waveform. This constant is a measure of the entergy handling capability of a transformer or inductor. It is dependent upon the core area, core material (including the saturation flux density of the core), the number of turns of the winding and tile duty cycle of the applied pulse. |
| Volt-Ampere (VA) |
| In an a.c. circuit, a measure of apparent power, given by: VA-EI, where E is the potential in volts; I is the curernt in amperes; and VA is apparent power in volt-amperes |
| Volt-Microsecond Constant |
| The product of the voltage applied across the winding and the time for the magnetizing current to reach 1.5 times the linear extrapolation of the current waveform. This constant is a measure of the energy handling capability of a transformer or inductor. It is dependent upon the core area, core material, number of turns, and the duty cycle of the applied pulse. |
| Voltage Balance |
| For a multiple output converter, the percentage difference in voltage level of two outputs with opposite polarities and equal nominal values. |
| Voltage, Maximum |
| The highest voltage that can safely be dropped across a PolySwitch device in its tripped state under specified fault conditions. |
| Synonyms: Maximum Device Voltage,Maximum Interrupt Voltage,Vmax |
| Voltage, Maximum Operating |
| The maximum voltage across a PolySwitch device under a typical fault condition. In many circuits, this is the voltage of the power source in the circuit. It may be possible to use a PolySwitch device at a higher voltage, but each such use must be individually qualified. |
| Volume Resistivilty (Core) |
| The ability of a core to resist the flow of electrical current either through the bulk of the material or on its surface. The unit of the volume resistivity is Ohm-cm. Core volume resistivity becomes an issue in inductor designs where the leads/terminals come in contact with the core material. This type includes axial and radial inductors that have leads epoxied into the core. As for core materials, high permeability ferrites present the most concern as their volume resistivity is typically the lowest.%0aUnder certian conditions, a low resistive path can be realized between two inductor terminals if theyare in contact with a low resistivity core. The inductor, under these condidtions, will lose its higher impedance characteristics. |
| VPN |
| virtual private network |
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| WAN |
| Wide Area Network- A network which encompasses interconnectivity between devices over a wide geographic area. |
| Warmup Time |
| Time required for a converter to operate within specifications after turn-on. This time normally precedes a long-term drift specification. |
| Weber |
| The practical unit of magnetic flux. It is the amount of magnetic flux, which, when linked at a uniform rate with a single turn electric circuit during an interval of one second, will induce an electromotive force of one volt. |
| Winding Factor (K) |
| The ratio of the total area of copper wire inside the center hole of a toroid to the window area of the toroid. |
| Window Area (Wa) |
| The area in and around a magnetic core which can be used for the placement of windings. |
| Withstand Voltage |
| Maximum voltage level that can be applied between circuits or components without causing a breakdown. Also see Breakdown Voltage and Isolation. |
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| xDSL |
| Refers to the various flavors of DSL (Digital Subscriber Loop). All encompassing term. |
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| XML |
| extensible markup language |
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| Zener Diode |
| A diode that maintains a relatively constant voltage when the reverse voltage across it is increased passed a specific point, called the zener voltage. |
| Zero Voltage Switching |
| Technique in which the power switch in a converter turns on and off when there is a zero voltage across it. This minimized switching transient noise output from the converter. |
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