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Circuit Protection Terminology

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.

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 �Rx�) are supplied with resistance values that are within specified limits of the product�s 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.

radio frequency

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.)

RFP

request for proposal

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

Synonyms: Initial Resistance,Base Resistance,Rmin,or Resistance

Rmin

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.

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 inductor�s 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 Raychem�s 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