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Glossar der elektronischen Begriffe

1-Wire

A single-wire communications protocol. For example, data and addressing can be sent by different timings of the pulses on the wire. Return path is via a common ground connection.

2-Wire

Two wire communication protocol, e.g. I²C or 4-20mA Loop. Data and addressing can be sent by two wires (Clock + Data) with a common ground return or by modulating the current in an isolated 2-wire loop.

3-Phase

In a three-phase power supply system, three live conductors each carry an alternating current of the same frequency and voltage but with a phase difference of one third the period (120°). The common reference can be earth because if the load is the same on all three phases, the net result is zero. Therefore a Neutral wire is not required.

60950-1

The main safety standard that covers power supplies in general. The international version (IEC60950-1), the North American version (UL60950-1, CSA C22.2 No. 60950) and the European version (EN60950-1) are all very similar, but separate certificates.

62368-1

The replacement for the 60950 standard after July 2018. The new standard is Hazard Based (HB) which means that in addition to the electrical and fire safety tests carried out by 60950, an extra risk assessment must be made to analyse any possible faults and their consequences.

60601-1

The main safety standard that covers medical grade power supplies. The international (IEC60601-1), North American (AAMI/ANSI 60601-1) and the European versions (EN60601-1) are all very similar, but separate certificates. The current version is the third edition (3rd Ed.)

60601-1-2

The main EMC standard that covers medical grade power supplies. The current version is the fourth edition (4th Ed.)

61010-1

The main safety standard that covers Test and Measurement Equipment.

60355-1

The main safety standard that covers Household Equipment (often also required by building automation applications)

8750

UL8750 is the UL safety standard covering LED lighting power supplies.

61347-1/

61347-2-13

The main international safety and EMC standard that covers LED lighting power supplies. The international (IEC61347-1) and the European versions (EN61347-1) are very different from the UL8750. IEC/EN 61347-2-13 covers EMC and harmonics interference.

50155

EN50155 is the European standard for Railways (rolling stock), commonly accepted worldwide.

AC

Alternating current. Single phase mains (115V in USA, 230V in Europe) alternates its polarity 60 times a second (USA) or 50 times a second (EU).

Access

Safety certification defines various levels of accessibility. Anything that is easily accessible must be safer than something that is with restricted access (behind a locked door, at an unreachable height or requiring tools to gain entry, for example)

The definitions include:

  • Operator Accessible – access can be gained without the use of a tool.
  • Restricted Access – access is through a tool or lock and key and the service person has been instructed about the necessary precautions.
  • Service Access – same as restricted access, but it is necessary that the equipment must be kept switched on to adjust or calibrate the system.
 

A/D Converter

Analog to digital. Specifically: A/D converter, a circuit that converts analog signals into digital data (not to be confused with an AC/DC converter)

AEC-Q100

An automotive-grade qualification test sequence for integrated circuits developed by the AIAG automotive organization. AEC-Q100 covers ICs, AEC-Q200 covers passive components. There is no standard for modules.

Air Discharge

A method for testing ESD-protection in which the ESD generator creates a spark which arcs over to the device under test (DUT).

Ambient Temperature

Temperature of the air surrounding a power supply. The operating temperature given in datasheets of RECOM parts is always the ambient temperature. The maximum case temperature can also be specified (temperature of the case or baseplate). Ambient is measured close to, but not directly above the converter

Ampere

Ampere(s), the unit of electrical current. Current is defined as the amount of charge that flows per unit of time. The symbol “I” is used for current in equations and “A” or “amp” is the abbreviation for ampere.

Ampere-hour

Commonly used to define battery capacity. One ampere-hour (1Ah) is a current of one ampere flowing for one hour. The amount of charge transferred in that hour is 3,600 coulombs (ampere-seconds).

Amplifier Class

Amplifier circuit types are divided into "classes" which describe whether the amplifier operates in a linear or switching mode, and any techniques used to restore linearity of output. Most common classes are Class A (analog high quality audio amplifiers) and Class D (digital switching amplifier)

ANSI

American National Standards Institute.

ASIC

Application-specific integrated circuit. Typically, a full custom or a semi-custom IC made up from pre-defined functional blocks.

ATE

Automated Test Equipment. Commonly used in a production line to check the correct functionality of each product manufactured (100% test)

Auto-transformer

An autotransformer is a transformer that uses a common winding for both the primary and secondary windings (no isolation). An autotransformer is often used to convert from 115V to 230V or vice-versa.

AWG

American Wire Gauge: A measure of wire thickness (which also dictates cross-sectional area, and for a given material, ampacity). Example: 24 AWG wire has a nominal diameter of 0.02in or 0.511mm.

Bandwidth

Bandwidth (BW) is a range of frequencies, or information, that a circuit can handle or the range of frequencies that a signal contains or occupies.

When measuring low-frequency ripple and noise, high frequency interference can give false readings, so the input of the oscilloscope is restricted to a bandwidth of 20MHz using a special filter: “20 MHz B/W Restricted”

BMS

Battery Monitoring System. A system that monitors the voltage on the individual cells of a battery and ensures that they are equally charged and discharged. Often requires an isolated DC/DC to interface with the controller.

BGA

Ball Grid Array: A packaging technology where the IC connections are made by a grid of solder balls underneath the chip.

Bidirectional

A device that accommodates signals traveling either direction though a single channel. A bidirectional DC/DC converter can transfer power in either direction.

Bipolar Transistor

A Bipolar Junction Transistor, or BJT, is a solid-state device in which the current flow between two terminals (the collector and the emitter) is controlled by the amount of current that flows through a third terminal (the base).

BJTs come in two flavors: NPN (symbol arrow faces outwards) and PNP (symbol arrow faces inwards). NPN transistors are commonly used to switch a signal to ground. PNP transistors are commonly used to switch a signal to +V.

Bluetooth/ Bluetooth LE

A technology that allows voice and data connections between a wide range of mobile and stationary devices through short-range digital two-way radio. A Bluetooth LE (Low Energy) module is an essential part of most IoT products. It requires either unregulated 4-6Vdc or regulated 3.3V supply. The current varies from 1µA or less in sleep mode up to 10-15mA peak when active.

Boost Converter

A power supply that steps an input voltage up (boosts it) to a higher, regulated voltage. The input voltage must always be lower than the output voltage.

Brownout

A condition where the voltage supplied to the system falls below the specified operating range, but above 0V.

Buck Converter

A "buck" or "step-down" switch-mode voltage regulator is one in which the output voltage is always lower than its input voltage.

Buck-Boost

A switch-mode voltage regulator in which output voltage can be above or below the input voltage.

Burst Mode

If an AC/DC converter is operated without a load, it may have a burst mode function where the main oscillator is switched on only for a short burst and then switched off. This reduces the no-load power consumption considerably.

Bus

Data or power path that connects to a number of devices.

CAD/CAM

Computer-aided design/ Computer-aided manufacture.

CAN bus

Controller Area Network bus. The CAN protocol is an international data communications standard defined by ISO 11898.

Crosstalk

A phenomenon where a signal on one conductor is inductively or capacitively coupled to an adjacent conductor.  In transformers, leakage capacitance between the windings allows interference generated on the input to appear on the output. A low isolation capacitance reduces this effect.

Capacitor

A capacitor is a passive electronic component that consists of two conductive plates or foils separated by an insulating dielectric. A voltage applied to the plates develops an electric field across the dielectric and causes the plates to accumulate a charge. When the voltage source is removed, the field and the charge remain until discharged, storing energy. Capacitance is measured in Farads, but typical values are microfarads (µF), or nanofarads (nF).

CAT5/7

Category 5: Refers to Ethernet cabling that satisfies the criteria for the EIA/TIA-568 standard's Category 5, which allows data transfers up to 100Mbps. The next generation is CAT7 cable which allows up to 1Gbps.

CC/CV

Constant current/constant voltage.

CCD

Charge Coupled Device: One of the two main types of image sensors used in digital cameras. When a picture is taken, the CCD is struck by light coming through the camera's lens. Each of the thousands or millions of tiny pixels that make up the CCD convert this light into electrons. The accumulated charge at each pixel is measured, then converted to a digital value.

CCFL

Cold Cathode Fluorescent Lighting: Often used as a backlight for LCD displays.

CCM

Continuous-conduction mode; a topology used in power converters.

CCTV

Closed circuit television: often used in building security systems

Charge Pump

Using switched capacitors to double the voltage. A low cost, low power DC/DC boost converter.

Class A EMC

Class A EMC limits define the maximum interference (conducted and radiated emissions) and immunity to interference (conducted and radiated susceptibility) for industrial applications.

Class B EMC

Class B EMC limits define the maximum interference (conducted and radiated emissions) and immunity to interference (conducted and radiated susceptibility) for domestic and commercial applications. Class B limits are harsher than Class A.

Clock Jitter

When a wanted phenomenon: Fluctuating or jittering the frequency of a clock to reduce EMI by spreading the main clock frequency over a wider range which makes it easier to filter out (also called spread spectrum).

When an unwanted phenomenon: the inaccuracy of a timing clock pulse.

CMOS

Complementary metal-oxide semiconductor (MOS) technology in which p- and n-channel transistors are used in tandem.

CMRR

Common Mode Rejection Ratio: The ability of a regulator to ignore rapid changes of the input voltage and not pass them on to the output.

Common-Mode Interference

Common-mode interference is identical signal components on both the positive and negative inputs and outputs of a power supply.  It cannot be filtered out with a simple capacitor-based filter, so a special inductor-based filter called a common-mode choke is needed instead.

Contact Bounce

When a mechanical switch or relay closes, the switch elements will often bounce before making final contact. This is of consequence if downstream power converters are sensitive to the switching transients. A contact de-bouncing circuit (also called a snubber) is often used to reduce the effect.

Contact Discharge

An ESD test method where the ESD generator makes direct contact with the device under test (DUT).

Crowbar

A crowbar circuit is a power supply protection circuit that rapidly short-circuits ("crowbars") the supply line if the voltage and/or current exceed defined limits. In practice, the resulting short blows a fuse or triggers other protection, effectively shutting down the supply. It is usually implemented by an SCR (a latching device that can only be reset by powering off)

Current-Mode Controller

A DC-DC switching regulator which regulates its output voltage by varying the peak inductor current on a cycle-by-cycle basis to output a regulated voltage despite variations in load-current and input-voltage.

Current-Sense Amplifier

An amplifier that measures current by measuring the voltage drop across a shunt resistor. The current sense amp outputs either a voltage or a current that is proportional to the current through the shunt.

D/A Converter

Digital-to-Analog Converter (DAC): A data converter that receives digital data and outputs a voltage or current proportional to the value of the data.

DALI

Digitally Addressable Lighting Interface. A 2-wire communication protocol that can control up to 64 devices (lights, switches, relays, sensors, etc.). DALI’s main advantages are that the data wires can be laid next to power wires (or in the same 5-wire cable), the system addresses itself and it is an international IEC Standard.

DC

Direct Current. A supply where the output voltage remains positive over time, e.g, from a battery or voltage regulator.

DCM

Discontinuous-conduction mode (a converter which allows the output current to fall to zero on each cycle, so that it becomes discontinuous)

Diode

A diode is a device that passes current in one direction only.

DFMEA

Design Failure Mode and Effects Analysis (DFMEA) is a method for evaluating a design for robustness against potential failures.

DIP24

DIP24 (Dual Inline Package) is a package design with two rows of 12 pin positions. Other common packages are DIP14 or DIP16 (2x7 or 2x8pins)

DPST

Double-pole/single-throw. A switch with two sets of contacts which can be opened or closed together.

DPDT

Double-pole/double-throw. A switch with two sets of contacts which can be switched together between two terminals with a center common connection.

Drain

One of the three terminals that comprise a FET. A voltage on the gate controls the current flow between the source and drain.

Drypack

Drypack is a method for packing integrated circuits in a moisture-free environment. The device is baked and immediately sealed in a vacuum-sealed bag. This process is reserved for package types which are especially susceptible to moisture intrusion. Maxim devices with MSL (Moisture Sensitivity Level) of 2 or higher usually require drypack.

Dual Phase Converter

Switching regulator that employs a two channel output which each output is 180° phase shifted to reduce output noise and boost output current capability.

ECO

(PCN)

Engineering Change Order: An instruction/permission given to production to change a part. Can be followed by a Product Change Notice (PCN) if the specification is altered as a result.

EIA

Electronic Industries Alliance: Among other things, the EIA sponsors electrical and electronic standards.

EIA-JEDEC

Electronic Industries Association/Joint Electron Device Engineering Council.

Efficiency

The ratio of output power to input power, the standard symbol is the Greek letter ƞ. With no load, the efficiency is always zero (the input side is active, but the load draws no power)

Embedded System

A system in which the computer (generally a microcontroller or micro-processor) is included as an integral part of the system.

EMC

Electromagnetic Compatibility: The ability of electronic equipment to be a "good electromagnetic neighbor": It neither causes, nor is susceptible to, electromagnetic interference within the limits of applicable standards.

EMI

Electromagnetic Interference: Unwanted noise from electromagnetic radiation.

Energy Harvesting

Energy harvesting (also known as power harvesting or energy scavenging) is the process in which energy is captured from a system's environment and converted into usable power. Energy harvesting allows electronics to operate where there's no conventional power source, eliminating the need to run wires or to replace batteries.

An energy harvesting system generally includes circuitry to charge a storage capacitor or battery.

Energy source examples include light (captured by photovoltaic cells), vibration or pressure (captured by a piezoelectric element or an oscillating mass with a pick-up coil), temperature differentials (captured by a thermo-electric generator or TEG) or radio energy (captured by an antenna).

EOL

End of Life. Issued when a part will no longer be manufactured.

EPROM/

EEPROM

Erasable Programmable Read-Only Memory. Electrically Erasable Programmable Read-Only Memory.

ESD

Electrostatic Discharge: Release of stored static electricity. ESD

is generated when two surfaces rub together to build up charges of thousands of voltage which  then suddenly sparks over.

ESD Protection

Devices added to input and output pins on an IC to protect the internal circuitry from the damaging effect of electrostatic discharge.

ESR

Effective Series Resistance (or Equivalent Series Resistance or ESR) is the resistive component of a capacitor's equivalent circuit.

A capacitor can be modeled as an ideal capacitor in series with a resistor and an inductor. The resistor's value is the ESR.

EV

Electric Vehicle. A plug-in EV (PEV) is a pure EV. A hybrid EV (HEV) has both an internal combustion engine and an electric motor. If the internal battery can also be recharged from the mains, it is a plug-in HEV (PHEV).

In China, EVs are called New Energy Vehicles (NEV).

Evaluation Kit

Evaluation Kit (EV Kit, Development Kit): A printed circuit board with an integrated circuit and support components to produce a working circuit for evaluation and development.

Exposed Pad

Offered in some IC packages to improve thermal dissipation or lower the impedance of the ground connection. Normally not electrically isolated, the pad typically needs to be connected to a ground or power plane, depending on the device.

Fail-Safe

A design that does not generate a hazardous condition under fault conditions. Fail-safes include fuses, over-voltage clamps or over-temperature trips.

FET

Field-Effect Transistor: A transistor in which the voltage on one terminal (the gate) creates a field that allows or disallows conduction between the other two terminals (the source and drain).  The most common FET is the MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) which comes in two flavors: N-type (most common) and P-type.

FFT

The Fast Fourier Transform (FFT) is a common algorithm for translating a signal from the time domain (signal strength as a function of time) to the frequency domain (signal strength as a function of frequency). It shows the signal's spectral content, divided into discrete frequency bands.

Filter

A filter blocks a certain range of frequencies. It can be low-pass (only low frequency signals get through, e.g. a bass filter), high-pass (only high frequency signals get through. e.g. a treble filter) or band-pass (only a certain frequency range of signals get through, e.g, an equalisation filter).

Low-pass filters are commonly used to block EM interference.

FIT

Failures in time (number per million hours). The inverse of MTBF (Mean Time between Failures).

Floating

An output is said to be "floating" if it is not connected to any input voltage supply, ground, or ground-referenced signal source.

Fold-back Current Limit

A circuit which reduces the current limit to a lower value once the set current limit has been exceeded. Usually the converter must be disconnected to reset the original current limit.

Forward Converter

A power-supply switching topology that transfers energy to the transformer secondary only when the switching transistor is on.

FPGA

Field Programmable Gate Array: A family of general-purpose logic devices that can be configured by the end user to perform many, different, complex logic functions.

GaAs

Gallium arsenide: A semiconductor material used for optoelectronic products such as LEDs, and for high-speed electronic devices.

Gain

The amount of amplification accomplished by an amplifier circuit or transistor. For instance, a gain of 200 would mean the output current is scaled to 200x the amplitude of the input current.

Galvanic Isolation

A galvanically isolated converter has no direct electrical connection between input and output.  

Gate

1. The controlling terminal of a FET. A voltage on the gate controls the current flow between the source and drain.

2. A basic logic element (e.g. AND, OR, NOT, NAND, NOR, XOR, etc.).

GPIB

General Purpose Interface Bus: A standard bus for controlling electronic instruments with a computer. Also called IEEE-488 bus because it is defined by ANSI/IEEE Standards 488-1978, and 488.2-1987. Also called HP-IB, a trademarked term of Hewlett-Packard, which invented the protocol.

GPIO

General Purpose I/O: A flexible parallel interface that allows a variety of test equipment (bench power supplies, meters, etc.)  to be controlled by a central computer.

GPS

Global Positioning System: A satellite- based navigation system in which two or more signals, received from satellites, are used to determine the receiver's position on the globe.

GUI

Graphical user interface

H

Henry: The unit of inductance. Most EMC filters require inductors or “chokes” in the range of µH (microhenries) up to a few mH (millihenries).

Half-Bridge

A power drive topology where one side of the inductor or transformer is alternately switched from V- to V+.

Half-Duplex

Data transmission over a circuit capable of transmitting in either direction, but not simultaneously.

Harmonic Distortion

The presence of frequencies in the output of a device that are not present in the input signal, and are multiples of components of the input signal. Clipping is a common cause but other nonlinearities can also introduce harmonics.

HART

Highway Addressable Remote Transducer (HART) communication is a commonly used mode of transmission for digital signals that are superimposed on the analog signal of a 4–20mA current loop. This allows both instantaneous analog readings with supplementary digital data on the same wiring system.

HALT/HASS

Highly Accelerated Lifetime Testing/ Highly Accelerated Stress Screening.   A way to calculate the expected lifetime or reliability of a product by combining several stress factors such as high temperature, high humidity and shock/vibration. Used to work out the warranty period for a brand-new product, for example.

Hi-Pot test

Abbreviation for High Potential test: the standard test for insulation breakdown voltage. A high voltage is applied across the isolation barrier for 1s or 1min and no arc-over should occur. All RECOM products are Hi-Pot tested.

HB LED

High-Brightness Light Emitting Diode

HDTV

High-definition television: an all-digital system for transmitting a TV signal with far greater resolution than the analog standards (PAL, NTSC, etc.)

Heat Sink

A metal block thermally connected to a heat producing component, designed to conduct heat away from the device. Most heat sinks are aluminum with fins to increase surface area and encourage the transfer of heat to the surroundings.

HEMT

High-electron-mobility transistor (also galled GaN)

HF/VHF/

UHF

High frequency is anything above 2MHz. VHF (Very High Frequency) is in the range 30-300MHz and UHF (Ultra High Frequency) is 300MHz to 3GHz.

Hi-Z

Hi-Z (or High-Z or high impedance) refers to an output signal state in which the signal is not being driven. The signal is left open, so that another output pin (e.g. elsewhere on a bus) can drive the signal or the signal level can be determined by a passive device (typically, a pull-up resistor).

High-Side

An element connected between the supply and the load. High-side current sensing applications measure current by looking at the voltage drop across a resistor placed between the supply and the load.

HomePlug

HomePlug (Powerline) is an industry-standard method for transmitting data via the house power lines. It can transmit audio, video, control signals, etc. HomePlug is a trademark of the HomePlug Powerline Alliance; Powerline is the generic term for the method. 

Hot-Swap

A power supply consisting of two or more power units wired in parallel which can be removed and replaced while the system remains powered up.

Human Body Model

An ESD test method where the ESD generator consists of a 100pF capacitor and a 1.5kohm series resistor which matches the real-life values of a charged human being.

HVAC

Heating, Ventilation, and Air Conditioning: Industry term for the systems and technology responsible for the heating, ventilation, and air conditioning in buildings.

Hysteresis

A threshold point can be shifted downwards when triggered by a rising signal or shifted upwards when triggered by a falling signal to eliminate multiple triggering caused by slowly moving inputs.  The amount of shift is called the hysteresis. Examples include enable pins (trigger point shifts from 1.2V to 1V on a rising signal and stays there until the input falls below 1V, when it jumps back to 1.2V) or over-temperature protection (OTP is set to 130°C, but the temperature has to fall below 110°C before the converter restarts)

Hz

Hertz: A measure of frequency. An older term is cycles per second, or cps.

I²C

I²C (pronounced "I-squared-C" and typeset as I²C but often typed as I2C) is short for "inter-IC bus." I²C is a two-wire, low-speed, serial data connection IC bus used to interconnect integrated circuits, generally on the same board.

IQ

Quiescent current. IQ (Q should be subscripted but sometimes printed as "IQ" without subscripting is the no-load input current consumed whenever a converter is idle.

IC

Integrated circuit: A semiconductor device that combines multiple transistors and other components and interconnects on a single piece of semiconductor material.

IEC

The International Electrotechnical Commission (IEC) prepares and publishes international standards for all electrical, electronic and related technologies. IEC standards are accepted in 34 countries (including Europe, Australia, Canada, USA, India, Israel, Korea and USSR) and also known as “CB Reports”, where CB means IECEE Certification Board approved.

IEEE

The Institute of Electrical and Electronics Engineers,  IEEE (Eye-triple-E) is a non-profit, professional association of more than 360,000 individual members in approximately 175 countries. IEEE also sponsors many electrical and electronic standards.

Impedance

Impedance, represented by the symbol Z, is a measure of the opposition to electrical flow. It is measured in ohms. For DC systems, impedance and resistance are the same (R=V/I). In AC systems, "reactance" enters the equation due to the frequency-dependent contributions of capacitance and inductance. Impedance in an AC system is still measured in ohms and represented by the equation Z = V/I, but V and I are frequency-dependent.

Inductive Kickback

The very rapid change in voltage across an inductor when current flow is interrupted. Snubber diodes are often used to channel this energy in relays, and other inductive loads. Kickback can be a problem (causing EMI and component failure); or it can be used in power supply circuits to develop higher or opposite-polarity voltages from a single supply.

Ingress Protection

An Ingress Protection (IP) rating indicates how well an enclosure is protected from penetration by foreign objects (first number) and by contaminants such as dust or fluids (second number). Common IP ratings are:

IP20 = protected against fingers touching live parts, but not against moisture.

IP44 = protected against 1mm particle ingress and splashing water.

IP67 = Dust tight and protected against water ingress up to 1m immersion

Inrush Current/

Soft-start

A momentary input current surge, measured during the initial turn-on of the power supply. This current reduces to a lower steady-state current once the input capacitors charge. The inrush current can be very high (10x steady-state input current) but usually lasts only a few milliseconds. If a converter has a soft-start circuit, the inrush current peak can be substantially reduced.

Intellectual Property

Intellectual Property, IP, are creations of the intellect such as trade knowledge, technical information, and literary or artistic work, including patents, copyrights, and trademarks. The “Know-how” in our business.

Internet Protocol

Standard method for data transfer used on the Internet. Also known as IP or TCP/IP.

Inverting Switching Regulator

A switch-mode voltage regulator in which output voltage is negative with respect to its input voltage. All of our R-78 and R-5/6/7xxx switching regulators can be configured to generate a negative output voltage from a positive input voltage.

IR

Infrared: Light that has a frequency below the visible light spectrum, used for remote controls and night vision applications, for example.

ISM

Industrial, Scientific and Medical: Radio frequency bands made available for use by communication equipment without license, within certain maximum emitted power limits. Equipment which uses the ISM band must tolerate interference from other such equipment.

Common uses include WiFi (802.11a, b, and g) and cordless phones.

ISO

International Standards Organization. ISO9001 is the main quality control standard for companies and organisations.

JEDEC

Joint Electron Device Engineering Council. JEDEC J-STD-020D is the main standard for SMD soldering

JFET

A JFET, or junction field-effect transistor, or JUGFET, is a FET in which the gate is created by reverse-biased junction (as opposed to the MOSFET which creates a junction via a field generated by conductive gate, separated from the gate region by a thin insulator).

Joule

Joule (abbreviated J): A measurement of energy or work. One joule is one watt of power, applied for one second (a watt-second). The energy absorption capability of transient protection components (diodes, Varistors, etc.)  is measured in Joules.

JPEG

Joint Photography Experts Group; more commonly, files that are compressed using the JPEG standard.

K, k

Kelvin: Temperature scale. Zero K is defined as absolute zero. +273.15K is 0°C. The K symbol is uppercase and used without a degree symbol.

Kilo: Metric unit representing 1000. E.g.: 1kHz is a 1 kilohertz (1000 Hertz). Note that the k is always lowercase.

Keep-Out Zone

The area under a converter on the circuit board that the layout design cannot use, due to the danger of short circuiting to the case or to high voltage pins.

LDO

Low Drop Out: A linear voltage regulator that will operate even when the input voltage barely exceeds the desired output voltage.

Leakage Inductance

Leakage inductance in a transformer is an inductive component that results from the imperfect magnetic linking of one winding to another.

In an ideal transformer, 100% of the energy is magnetically coupled from the primary to the secondary windings. Imperfect coupling reduces the signal induced in the secondary windings. The electrical equivalent is some self-inductance in series with the primary windings that are properly coupled. This series inductance is the "leakage inductance."

LED

Light-Emitting Diode. A diode which emits electroluminescence with a frequency (color) determined by the band-gap energy of the p-n junction.

White light LEDs are made by either combining three red, green, blue LEDs in one package or by using a phosphor coating to converter UV to visible light

Line Regulation

The ability of a power-supply voltage regulator to maintain its output voltage despite variations in its input voltage.

Linear Regulator

A voltage regulator that is placed between a supply and the load and provides a constant voltage by varying its effective resistance. Excess power is dumped as heat, so typical linear regulators are only 60% efficient or less.

Lithium batteries

Lithium batteries for low-power, high-reliability, long-life applications such as non-volatile memory and timekeeping (typically in coin-shaped cells) use a variety of lithium-based chemistries (as differentiated from lithium-ion). 

Lithium-ion batteries

Lithium-ion (Li+, Li-Ion, Lion) cells are generally used as power sources for portable equipment. They are usually rechargeable. Lithium-ion and nickel-metal-hydride (NiMH) have displaced nickel-cadmium (NiCd or nicad) as the dominant rechargeable chemistry for portable applications.

Load Regulation

The ability of a power-supply voltage regulator to maintain its output voltage despite variations in the load current.

Low Line

The minimum allowable input voltage. At full load, this is the highest input current condition.

Low-Side

In a switching circuit (especially IGBT or SiC), the transistor that switches between the load and ground.

M2M

Machine-to-machine communications, where smart nodes talk to each other via wireless technologies such as cell phone network technologies, WLAN, Bluetooth or Zigbee without human interaction.  Applications include automatic meter reading, fleet management, vending, monitoring and control, security and alarms, and telemedicine.

mA

Milliampere, or milliamp: 1/1000 of an Ampere. Ampere is the basic unit for measuring electrical current. The “m” is always lower case.

Manchester Data Encoding

Manchester encoding is a form of binary phase-shift keying (BPSK) used for low-cost radio-frequency (RF) transmission of digital data. Its main characteristic is that it encodes data in a way that insures there will never be long strings of continuous zeros or ones. The guaranteed transitions means that the clock can be recovered from the transmitted data, allowing the link to function with variable signal strengths from transmitters with imprecise, low-cost, data-rate clocks.

Margining

Margining is a test procedure that determines the "safety margin." A parameter is varied to determine the device's sensitivity or ability to perform given a range of inputs. A large number of parts can be characterized to determine a safe range for the specification, to guarantee performance and yield.

MEMS

Micro-electromechanical systems: systems that combine mechanical and electrical components on the same die and are fabricated using semiconductor fabrication techniques. Common examples are pressure and acceleration sensors which combine the sensor and amplification or conditioning circuitry.

Metal Oxide Varistor

A Metal Oxide Varistor (MOV, or surge-suppressor) is a discrete electronic component that diverts excessive voltage to the ground and/or neutral lines. It is commonly used on the inputs of AC/DC modules to suppress input voltage surges. A MOV can divert a lot of energy, but reacts slowly, so it is often used in combination with a transient suppressor diode that reacts quickly, but has limited power absorption characteristics.

MIMO

A Multiple Input, Multiple Output (MIMO) system has multiple antennas and multiple radios. MIMO is used in the implementation of the 802.11n wireless LAN standard.

MOSFET

Metal-oxide semiconductor field-effect transistor;

In a MOSFET, the conductive channel between the drain and source contacts is controlled by a metal gate separated from the channel by a very thin insulating layer of oxide. The gate voltage establishes a field that allows or blocks current flow, in effect a voltage-controlled switch.

MPU

Micro-Processing Unit (Nowadays, a Microprocessor)

Multipath

In radio transmission, multipath refers to the simultaneous reception of two copies of the signal that arrive via separate paths with different delays.

A common example is when a signal bounces off a building or other object and is received along with the direct (unbounced) signal. In television reception, this causes "ghosting" -- one sees a faded echo on the screen horizontally displaced from the main image. One of the main reasons why GPS does not work well in NYC is the multipath signals bouncing off all the tall buildings.

Murphy's Law

If anything can go wrong, it will.

mW

Milliwatt(s) is 1/1000 of a Watt

MW

Megawatt(s) is 1 million watts

(see: big “M” or little “m” make a BIG difference!)

nA

Nanoampere(s): Unit of measure. A billionth of an amp

NC

Not Connected. Used to denote a pin that is present only for mechanical stability. It is not normally electrically connected internally, but this is not a hard and fast rule. If it says “NC”, the pin should be soldered onto its own isolated pad and not connected to any other pin.

NPI

New Product Introduction — an info pack released with all new products.

NRE

Non-Recurring Engineering cost — one-time engineering costs associated with a project (usually for the design effort or for tooling or certifications)

NTC

Negative Temperature Coefficient thermistor. A resistor whose resistance decreases with increasing temperature. The nominal resistance value is always given at 25°C (room temperature).

Nyquist

In A/D conversion, the Nyquist principle (derived from the Nyquist-Shannon sampling theorem) states that the sampling rate must be at least twice the maximum bandwidth of the analog signal in order to allow the signal to be reproduced. The maximum bandwidth of the signal (half the sampling rate) is commonly called the Nyquist frequency.

OCP

Overcurrent Protection. A converter than can protect itself from being damaged by an overload condition. Typical techniques are either by power limiting the output (the output voltage is allowed to fall with increasing current) or by hiccup protection (the output is turned off and then back on again after a delay, if the overcurrent condition still exists, the cycle repeats).

OEM

Original Equipment Manufacturer. A manufacturer who makes products for other companies to brand-label as their own.

OLED

Organic Light-Emitting Diode: An LED made with organic materials. Useful for flat film displays, but still rather weak compared with standard LEDs

Op amp

Operational amplifier: An amplifier has positive and negative inputs which allow circuits that use feedback to achieve a wide range of functions.

Using op amps, it's easy to make amplifiers, comparators, logarithmic functions, filters, oscillators, data converters, level translators, voltage references and more. Analog mathematical functions like addition, subtraction, multiplication, and integration can also be easily accomplished.

A rail-to-rail op amp can work with input signals up to its own supply voltage.

Open-drain

An open-drain or open-collector output is driven by a single transistor, which pulls the output only down to ground. The output must be pulled up to +V by the load or by an external pull-up resistor.

OR-ing Diode

OR-ing diodes are used to connect the outputs of two separate power supplies to a single load. Thus, if either PSU1 or PSU2 is active, then the load has power. Used to add supply redundancy to a critical circuit to make it fail-safe.

Overvoltage Protection, OVP

Overvoltage Protector (OVP) refers to a circuit that protects downstream circuitry from damage due to excessive output voltage. At its simplest, it is a clamping Zener diode across the output. A more fail-safe technique is to add a separate opto-coupler which is triggered by an output overvoltage condition to shut-down the power supply on the input side because regulation has failed.

p-p

Peak-to-peak. Often used as a measure of the output voltage ripple.

Partial Discharge

A non-destructive way of testing for isolation strength. A Hi-Pot test is very destructive because if an insulator fails, the arc-over destroys the part. PD testing measures the charge migration through the insulation layers and will stop the test before any permanent damage occurs.

pC

pC: Picocoulomb(s), a unit of electrical charge (10-12 coulombs). Used as a measure of partial discharge in insulation testing.

PCM

Pulse-Code Modulation (PCM) is the conversion of an analog signal into binary (0 or 1) coded pulses. Not to be confused with PWM.

Pcs

Abbreviation for pieces.

Peak Inverse Voltage

Peak Inverse Voltage (PIV) or Peak Reverse Voltage (PRV) refer to the maximum voltage a diode or other device can withstand in the reverse-biased direction before breakdown. Also may be called Reverse Breakdown Voltage.

PFM

Pulse-Frequency Modulation: A pulse modulation technique in which the frequency is varied with the input signal amplitude. The duty cycle of the modulated signal does not change. Commonly used to reduce the quiescent input current in a converter by reducing the switching frequency at low loads.

PFMEA

Process Failure Mode and Effects Analysis (PFMEA): A methodology for assessing the weaknesses of production processes and the potential effects of process failures on the product being produced.

PG

Power-good: a pin that is only active when the output voltage is within range.

PHY

Physical Layer. An interface circuit or SoC used to connect to the internet

PLC

A Programmable Logic Controller (PLC, or Programmable Controller) is a ruggedized, DIN-Rail mounted, microprocessor-based control system for plant automation by monitoring sensors and controlling actuators (relays/pneumatic /hydraulic valves) in real time. Commonly used with 24V DIN-Rail supplies.

PLCC

Plastic Leaded Chip Carrier: A square surface mount chip package in plastic with leads (pins) on all four sides.

PLL

A phase-locked loop (PLL, or phase lock loop) is a control system that generates a signal that has a fixed relation to the phase of a "reference" signal. A phase-locked loop circuit responds to both the frequency and the phase of the input signals, automatically raising or lowering the frequency of a controlled oscillator until it is matched in both frequency and phase.

p-MOS

A p-channel metal-oxide semiconductor (p-MOS) transistor is one in which p-type dopants are used in the gate region (the "channel"). A negative voltage on the gate turns the device on.

PoE

Power-over-Ethernet: A means for delivering power to a remote device using the same cable lines used to deliver Ethernet data. Can be used to power remote devices (cameras, LED-lighting, door entry systems) over a single combined power and bi-directional data cable.

The nominal PoE voltage supply is 44-57VDC, so a DC/DC converter is required at the end device. This DC/DC must negotiate with the primary power supply to release enough current for its needs (available power is restricted between 4W and 100W depending on a complex sequence of signature resistances offered by the DC/DC negotiation IC). The relevant standard defining this interface is called IEEE 802.3af /at/bt.

Many think that PoE is the future for indoor LED lighting.

Point-of-Load

Point-of-load (POL) power supplies deliver high peak currents and low noise margins, as required by high-performance ASICs and µcontrollers, by placing individual power supply DC regulators close to their point of use.

POK

Power-OK

Potentio-meter

Variable resistor in which a wiper sweeps from one end of the resistive element to the other, resulting in resistance that is proportional to the wiper's position. Commonly abbreviated to “pot”.

Power Fail

A feature in a microprocessor supervisory circuit that provides early warning to the microprocessor of imminent power failure.

PPAP

Production Part Approval Process. Used by automotive industry for acceptance of new products for release and use on automobiles.

PCB

Printed circuit board. The most common PCB material is FR4: a glass fibre  reinforced laminate which is flame resistant in compliance with UL94V-0

PROFIBUS

Vendor-independent open fieldbus standard used in manufacturing, building automation, and process control. Utilizes a non-powered two-wire (RS-485) network.

PTC

Positive Temperature Coefficient (PTC): When the resistance of a component rises with temperature, it is said to have a positive temperature coefficient.

Example: Hewlett-Packard's first commercial product, an audio oscillator, used a common light bulb as a PTC element in the feedback circuit to maintain constant output amplitude regardless of frequency.

Push-Pull

An output driver which uses one active device to source current and a second device to sink current. Commonly used in DC/DC converter as a power oscillator to drive the transformer primary winding.

PWM

A fixed frequency square wave signal with variable on time. In DC-DC switching regulators, the pulse width oscillator driving the main power switch (and hence, the duty cycle) is varied to maintain the desired output voltage.

Q Factor

A measure of the quality of a resonant (tank) circuit. A "high-Q" circuit has mostly reactive components (inductive and capacitive), with low resistance. It resonates strongly, with little damping, and will have low bandwidth relative to its center frequency (that is, it will have a narrow bandwidth vs frequency curve). Q = 2 π * (Energy stored / Energy dissipated per cycle)

QFN

"Quad, flat, no-lead" package.

Quiescent current

The current consumed by a converter when it in a no-load state, but still enabled.

RAID

Redundant Array of Independent Disks: A redundant array of inexpensive disks. RAID is a performance-enhancing method of storing the same data in different places on multiple hard disks to achieve speed and/or data redundancy.

Rail-to-Rail

The allowable input and output voltage ranges include the power-supply rails.

Commonly used to describe Op-amps that can be operated from single power rails (no negative supply).

RAM

Random access memory

RC

Resistance-capacitance. An RC network is a network composed of resistors and capacitors in a series-parallel combination to filter or delay a signal.

Reflected Ripple Current

DC/DC converters contain power oscillators that draw current peaks every cycle. The difference between the steady-state input current and the current peaks is the ripple current. As the input current is load-dependent, the input current “reflects” the output load current.

Resonant Circuit

A resonant, or tuned, circuit combines an inductor and capacitor to make a circuit that resonates at a particular frequency. Depending on the configuration, the circuit can have a high or low impedance at the resonant frequency and operate as bandpass or band stop filter, or an oscillator.

It may be called an LC, LLC or LRC circuit because of the inductive (L), resistive (R), and capacitive (C) components used.

Reverse Recovery Time

When switching from the conducting to the blocking state, the diode junction has stored charge that must first be discharged. This discharge takes a finite amount of time known as the Reverse Recovery Time, during which the diode does not block the reverse current. When dealing with high frequency oscillators or very steeply rising signals, the reverse recovery time can lead to significant losses in a circuit.

RFI

Radio Frequency Interference: Unwanted noise from RF sources.

RFID

Radio Frequency Identification: A method for remotely identifying an object using a tag or module that carries a unique ID code, which can be activated by an external RF field which both powers the tag and reads the code back.

rH

Relative humidity. Normal room humidity is between 40-60% rH.

RMS

Root mean square. Vrms is the effective constant voltage that would deliver the same power as the varying AC input (the average value of a 50/60Hz sine wave is zero as positive and negative half-cycles cancel out, so RMS must be used instead). For example, 115Vac is the RMS value of the mains supply. The peak voltage is actually ≈163V.

RS-232

The term "serial" interface is often used for an RS-232 interface, consisting of Tx, Rx and ground wires, plus optionally RTS and DSR handshaking lines. The usage is not quite accurate—while RS-232 is a serial interface, there are other serial interfaces in addition to RS-232 (e.g. RS-422)

RS-422/RS-485

RS-485 and RS-422 are serial interface standards in which data is sent in a differential pair (two wires, or twisted pair cable), which allows greater distances and higher data rates than RS-232.

RTC

Real-time clock: Integrated circuit that contains a timer that supplies the time/date – usually contains a long-life battery to allow it to keep track of the time even when there is no power applied.

S, s

Siemen(s), standard unit for conductance (the opposite of resistance).

Lower case s is the standard abbreviation for seconds.

SAW

Surface Acoustic Wave: A sound wave that propagates along a hard surface. Used to make touchscreens by timing when and where a finger stops the wave.

SCART

Also known as Euro-connector, a 21-pin connector commonly used in Europe to interconnect satellite receivers, television sets, and other AV equipment. Sometimes needs a DC/DC to supply a 10-12V “Device present” signal.

Schottky Diode

A "Schottky-barrier junction" is a metal-semiconductor junction, rather than the P-N junction used by conventional semiconductor diodes. Schottky diodes are often chosen for their high switching speed and low forward voltage drop (around 0.3V, compared to a diode’s typical 0.7V)

SCR

Silicon-controlled rectifier. A device that once activated stays on until the input voltage turns off or reverses, therefore can be used as a latch. Typical uses include fault protection (OVP, OTP) which forces the user to turn off the device to reset the SCR.

SD

Secure Digital, a media format for non-volatile external memory cards. SD memories typically operate from 3.3V supplies and are best known as storage for digital cameras, smart phones, and other consumer electronic devices.

Sense or Shunt Resistor

A resistor placed in a current path to allow the current to be measured. The voltage across the sense resistor is proportional to the current that is being measured. Typical value is in  milliohms.

SEPIC

Single Ended Primary Inductor Converter: A DC-DC converter topology that acts both as a boost and a buck converter (that is, will step up or down, depending on the input voltage).

Serial Interface

A serial interface (as distinguished from a parallel interface) is one in which data is sent in a single stream of bits, usually on a single wire-plus-ground, wire-pair, or single wireless channel (or two sets, one for each direction). Examples include USB, RS-232 and  I2C

Shoot-Through

In a push-pull oscillator stage, one transistor pushes current to the output to drive it toward a positive voltage; a second device pulls down. The drivers are designed so both devices are never on at the same time, which would effectively short the power supply, however timing delays can sometimes cause both to be on simultaneously. The rush of current that occurs while both devices are on is called the shoot-through current.

Signal-to-Noise Ratio

Signal-to-Noise Ratio, the ratio of the amplitude of the desired signal to the amplitude of noise signals. Usually expressed in decibels, dB. The larger the number, the better

SIM

Subscriber identity module. The SIM card identifies your cellphone so the system knows which phone should ring when someone dials your number.

“Smart”

Prefix that is used with many inanimate things (homes, offices, phones, cities) to mean some sort of embedded intelligence and interconnectability.

Smart Sensor

A sensor that processes the raw measurement data and only sends relevant updates to reduce the amount of data traffic. Important for the concept of  IoT if billions of devices are to be on the network.

SMBus

System Management Bus: A 2-wire serial-interface standard similar to I²C, but with a faster clock speed,

SMD

Surface Mount Device (SMD): An electronic component that mounts on the surface of a printed circuit board (as opposed to "through-hole" or THT components which have pins that are inserted into holes).

SMPS

Switch-Mode Power Supply. Much more efficient than linear power supplies, so almost exclusively used for anything above a few watts (with the exception of broadband RF amplifiers where the switching harmonics would interfere).

Snubber

A device which suppresses voltage transients and spikes. Usually a capacitor and resistor in series.

Soft Start

A feature in some switching power supplies that limits the startup inrush current at initial switch-on.

SoC

System on Chip. A complete computer, RF interface or system on a single IC.

SOIC

Small outline integrated circuit. If an SMD IC has 8 pins, it is often an SOIC-8

SPI

Serial Peripheral Interface. A 3-wire serial interface.

SPICE

Simulation Program with IC Emphasis. Software which allows a circuit to be simulated to predict its real-life behaviour.

Spread Spectrum

Spread-spectrum techniques can also be used to reduce electromagnetic interference by dithering the clock frequency so emissions are no longer concentrated at one frequency.

SPST

Single-pole/single-throw switch

SRAM

Static RAM: RAM that does not require a clock to retain its contents.

SS

Soft-start. Typically a pin on an IC which can be used to set the start-up timing to reduce the inrush current by adding an external capacitor.

SSOP

Shrink small-outline package

Star Ground

A layout or wiring technique in which all components connect to ground at a single point.

STB

set top box – typically a cable or satellite receiver.

Step-Up   DC-DC

A switch-mode voltage regulator in which output voltage is higher than its input voltage.

Switch Mode

Topology with a switching transistor and inductor to regulate the voltage/current.

Switching Regulator

A voltage regulator that uses a switching element to transform the supply into an alternating current, which is then converted to a different voltage using capacitors, inductors, and other elements, then converted back to DC. 

Synchronous Rectification

In switch-mode power supplies, the output rectifier diode is replaced with a FET switch to reduce losses and thereby increase efficiency. The FET is turned synchronously on and off to reproduce the effect of a diode.

System on a Chip

A System on a Chip (SoC) integrates most of a system's elements on a single integrated circuit (chip). It typically combines a microprocessor core along with interface elements and analog and mixed signal functions.

Tc

Abbreviated for case temperature. The hottest point and the maximum allowable temperature must be marked on all LED lighting AC/DC drivers.

TCP/IP

Transmission Control Protocol/Internet Protocol: The protocols or conventions that computers use to communicate over the Internet.

TEC

A thermoelectric cooler (TEC) is a small cooling device that relies on a semiconductor Peltier junction. Composed of two semiconductors made of different materials, a Peltier junction acts as a heat pump which can cool or warm when current is passed through it.

Tempco

Temperature coefficient, the amount a value drifts with temperature in %/°C

Tesla

Tesla (abbreviated T) is a measure of magnetic flux density (B-field), named for engineer and inventor Nikola Tesla.

TFT

Thin-film transistor

THD

Total Harmonic Distortion (THD): A measure of signal distortion which assesses the energy that occurs on harmonics of the original signal.

Thermal Management

The use of various temperature cooling methods, such as heatsinks, thermal interface materials (TIM) or fans to control the overall temperature.

Thermal Shutdown

Deactivating a circuit when a measured temperature is beyond a predetermined value. Can be latch-off or auto-reset upon cooling down.

Thermistor

A temperature-dependent resistor with a high temperature coefficient. Can also be used as a series inrush current limiter (high resistance when cold, low resistance when hot).

Thermo-couple

A temperature sensor formed by the junction of two dissimilar metals. A thermocouple produces a voltage proportional to the difference in temperature between the hot junction and the lead wire (cold) junction.

Three-State or Tri-State

A three-state output has three electrical states: One, zero, and "Hi-Z," or "open."  “Tri-State” is a registered trade mark.

Through-Hole

A method for mounting components on a printed circuit board (PCB) in which pins on the component are inserted into holes in the board and soldered in place.

Tin Whiskers

Tin whiskers (also called Sn whiskers or metal whiskers) are microscopic, conductive, hair-like crystals that emanate spontaneously from pure tin surfaces. There are various whisker mitigation processes that can be done to reduce this effect, such as matt finishes, under-plating or over-plating.

Totem Pole

A standard CMOS output structure where a P-channel MOSFET is connected in series with an N-Channel MOSFET and the connection point between the two is the output. The P-FET sits on top of the N-FET like a "totem pole." This creates a push-pull output using just two transistors.

TQFN

Thin version of the QFN package (the JEDEC "W" option) 0.8mm thick.

TQFP

Thin quad flat pack

Trans- conductance Amplifier

An amplifier that converts a voltage to a current. Also known by several other terms, such as OTA, or operational transconductance amplifier.
The term derives from "transfer conductance" and is measured in siemens (S), where 1 siemens = 1 ampere per volt. It is represented with the symbol gm. The basic gain of vacuum tubes and FETs is expressed as transconductance.

Transformer

An inductive electrical device for changing the voltage of alternating current, consisting of two magnetically coupled coils. Alternating current in one (called the "primary") creates a changing magnetic field which induces a current in the second coil (the "secondary").  Multiple secondary coils can be powered from a single primary winding.

There is no such thing as a DC transformer, so an isolated DC/DC converter has to convert the DC input to an AC signal and then rectify the resulting AC transformer output back to a DC output.

Transistor

A basic solid-state control device which allows or disallows current flow between two terminals, based on the voltage or current delivered to a third terminal.

TS 16949

TS 16949 is an ISO Technical Specification that aligns various automotive quality systems standards within the global automotive industry.

Together with ISO 9001:2000, ISO/TS 16949:2002 specifies the quality system requirements for the design/development, production, installation and servicing of automotive related products. RECOM’s factories in Taiwan are ISO/TS 16949 certified.

TSOP

Thin small-outline package

TTL

Transistor-to-transistor logic. Requires a 5V±0.25V supply.

TVS

Transient Voltage Suppressor: Semiconductor device designed to protect a circuit from voltage and current transients. Typically implemented as a large silicon diode operating in avalanche mode to absorb large currents quickly.

Tx

Transmit

uA

Microampere, or microamp: A millionth of an Ampere. Ampere is the basic unit for measuring electrical current.

Often written as uA, but the u is a plain-text substitute for the Greek letter mu.

UART

Universal Asynchronous Receiver-Transmitter: An IC that converts parallel data to serial and converts received serial data to parallel data.

Un-interruptible Power Supply

An uninterruptible power supply (UPS) is a device that maintains AC power in the event of a mains failure. A UPS commonly includes a battery that is kept charged and ready. When power fails, the battery powers an AC inverter to keep the mains voltage stable. This allows an orderly power-down of the system or to bridge short power outages.

URL

Universal resource locator —a web address

USB

Universal Serial Bus (USB): A standard port that enables the connection of external devices to computers.

The USB standard supports both data and power transfer. The new USB 3.1 standard allows up to 5V @ 3A (15W) plus 20V @ 5A (100W), as well as faster data transfer rates.

UV

Ultraviolet. The blue light that we cannot see.

UVLO

Undervoltage lockout

VA

Volt ampere(s). If the voltage and current are not is phase because the load is inductive or capacitive, then the power is measured in VA and not Watts.

Vcc, Vss

The supply voltage for a circuit is often given as V plus a double-letter suffix. The double letter is usually related to the lead of the transistors that are commonly connected to that supply, e.g. VCC is a positive-voltage supply and connects to the Collector terminal of bipolar transistors. VSS connects to the Source terminal of a FET, etc. V+ and V- are also used.

VCO

Voltage-Controlled Oscillator: An oscillator device in which output frequency is proportional to a control voltage.

VoIP

Voice over Internet Protocol: Method for transmission of telephone calls over the Internet, e.g. Skype.

Volt

Volt (or Volts): Unit of measure for electromotive force (EMF), the electrical potential between two points. An electrical potential of 1 volt will push 1 ampere of current through a 1-ohm resistive load.

Voltage Doubler

A capacitor charge pump circuit which produces an output voltage which is twice the input voltage. A low cost, low power DC/DC converter.

Voltage Regulator

A circuit which is connected between the power source and a load, which provides a constant voltage despite variations in input voltage or output load.

V p-p

Peak-to-peak voltage

VRM

Voltage Regulator Module. Another name for a switching regulator.

W

Watt (W) is the unit for measuring power. In physics terms, one watt is one Joule of energy transferred or dissipated in one second. Electrical power is calculated as: Watts = Volts x Amps x Power Factor

The power factor can be disregarded for DC circuits or for AC circuits with a resistive load (it is 1 in those situations).

Wafer

Semiconductor manufacturing begins with a thin disk of semiconductor material, called a "wafer." A series of processes defines transistors and other structures, interconnected by conductors to build the desired circuit.

The wafer is then sliced into "dice" which are mounted in packages, creating the IC.

WAN

Wide Area Network: Any Internet or network that covers an area larger than a single building.

WiMax

WiMax (Worldwide Interoperability for Microwave Access) is a broadband, wireless access defined by the IEEE 802.16 standards. Wi-Fi (802.11) covers a small area with a radius of a few hundred meters, but WiMax (802.16) can cover up to 6 miles with only one base station.

WLAN

Wireless Local Area Network

X Cap,

Y Cap

X-Capacitors are certified to be used across mains inputs. Y-capacitors are certified to be used between mains and ground or across an isolation barrier.

They are designed to self-repair after an over-voltage condition (self-healing).

Y-caps have extra insulation (double or reinforced) so are more expensive.

Zener Diode

A zener diode is a diode manufactured to have a specific reverse-breakdown voltage. Its most common use is as a voltage reference.

ZIF

Zero Insertion Force: A class of IC sockets which clamp the IC pins (via a small lever on the side of the socket) after insertion, and thus require no downward force on the IC or its pins to insert it into the socket.

ZIGBEE

A standard for short-distance, low-data-rate, mesh (not point-to-point) communications. Created and maintained by the ZIGBEE Alliance Group.

ZVS

Zero voltage switching: a switch that operates only when the AC input passes through 0V (Zero voltage crossing: ZVC)