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Circuit Protection Terminology

10 BASE-T

The Institute of Electrical and Electronic Engineers (IEEE) 802.3 specification for ethernet over thin coaxial cable.

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.

third generation

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 device's 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 device's 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 400�H 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)

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 Ampere's Law.

Amplitude Permeability (�a)

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.

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.

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

See enclosure.

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 �air core� 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 'choke', 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

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-�)

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

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 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 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 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 (�i) 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