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Circuit Protection Terminology

l Redundancy

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.

Outside diameter.

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)

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

OXC

optical cross-connect

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 Raychem�s 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).

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 core�s 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.

POP

point of presence

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

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.

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.