ADC术语表(AD-English)

HighSpeedAnalog-to-DigitalConvertersGlossaryABCDEFGHIJKLMNOPQRSTUVWXYZAAcquisitionTimeThistermrelatestosamplingA/Ds,whichuseatrack/holdamplifierontheinputtoacquireandhold(toaspecifictolerance)theanaloginputsignal.AcquisitiontimeisthetimerequiredbytheT/Hamplifiertosettletoitsfinalvalueafteritisplacedinthetrackmode.AnalogBandwidthTheanaloginputfrequencyatwhichthespectralpowerofthefundamentalfrequency(asdeterminedbytheFFTanalysis)isreducedby3dB.ApertureDelayThedelaybetweenthe50%pointoftherisingedgeoftheENCODEcommandandtheinstantatwhichtheanaloginputissampled.AnalogtoDigitalConverter(ADC,A/DConverter)Thisdeviceconvertsrealworldanalogsignalsintoadigitalformatthatcanbeprocessedbyacomputer.ApertureUncertainty(Jitter)Thesample-to-samplevariationinaperturedelay.CConversionSpeed(Rate)Thenumberofrepetitiveconversionspersecondforafull-scalechangetospecifiedresolutionandlinearity.CrosstalkCouplingontoonechannelbeingdrivenbyalowlevel(-40dBFS)signalwhentheadjacentinterferingchannelisdrivenbyafull-scalesignal.DDifferentialAnalogInputResistance,DifferentialAnalogInputCapacitance,andDifferentialAnalogInputImpedanceTherealandcompleximpedancesmeasuredateachanaloginputport.TheresistanceismeasuredPage1of7AnalogDevices:DataConverters:HighSpeedAnalog-to-DigitalConvertersGlossarystaticallyandthecapacitanceanddifferentialinputimpedancesaremeasuredwithanetworkanalyzer.DifferentialAnalogInputVoltageRangeThepeaktopeakdifferentialvoltagethatmustbeappliedtotheconvertertogenerateafullscaleresponse.Peakdifferentialvoltageiscomputedbyobservingthevoltageonasinglepinandsubtractingthevoltagefromtheotherpin,whichis180degreesoutofphase.Peaktopeakdifferentialiscomputedbyrotatingtheinputsphase180degreesandtakingthepeakmeasurementagain.Thenthedifferenceiscomputedbetweenbothpeakmeasurements.DifferentialNonlinearity(DNL)Thedeviationofanycodewidthfromanideal1LSBstep.DynamicRangeTheratioofthemaximumoutputsignaltothesmallestoutputsignalthatcanbeprocessedinasystem.UsuallyexpressedlogarithmicallyindB.Dynamicrangecanbespecifiedintermsofharmonicdistortion,signal-to-noiseratio,spurious-freedynamicrange,orotherACinput-basedperformancecriteria.EEffectiveNumberofBits(ENOB)Theeffectivenumberofbits(ENOB)iscalculatedfromthemeasuredSNRbasedontheequation:EncodePulseWidth(DutyCycle)PulsewidthhighistheminimumamountoftimethattheENCODEpulseshouldbeleftinlogic1statetoachieveratedperformance;pulsewidthlowistheminimumtimeENCODEpulseshouldbeleftinlowstate.Atagiveclockrate,thesespecsdefineanacceptableEncodedutycycle.FFastFourierTransform(FFT)Acomputationallyefficientmathematicaltechniquethatconvertsdigitalinformationfromthetimedomaintothefrequencydomainforrapidspectralanalysis.FFTsgenerallyuseatimeweightingfunctiontocompensatefordatarecordswithanon-integernumberofsamples;somepopularweightingfunctionsareHanningWindowand4-termBlackman-Harris.FlashConverterFlashADCsarethefastesttypeofADCanduselargenumbersofcomparators.AnN-bitflashADCconsistsof2Nresistorsand2N-1comparators.Page2of7AnalogDevices:DataConverters:HighSpeedAnalog-to-DigitalConvertersGlossaryFullScaleInputPowerExpressedindBm.Computedusingthefollowingequation:GGainErrorGainerroristhedifferencebetweenthemeasuredandidealfullscaleinputvoltagerangeoftheworstADC.GainMatchingExpressedin%FSR.Computedusingthefollowingequation:HHarmonicAfrequencythatisamultipleofthefundamental.HarmonicDistortion,SecondTheratioofthermssignalamplitudetothermsvalueofthesecondharmoniccomponent,reportedindBc.HarmonicDistortion,ThirdTheratioofthermssignalamplitudetothermsvalueofthethirdharmoniccomponent,reportedindBc.IIntegralNonlinearity(INL)Thedeviationofthetransferfunctionfromareferencelinemeasuredinfractionsof1LSBusingabeststraightlinedeterminedbyaleastsquarecurvefit.Page3of7AnalogDevices:DataConverters:HighSpeedAnalog-to-DigitalConvertersGlossaryLLeastSignificantBit(LSB)Theright-mostbitinadataconvertercode.LSBsizeisrelatedtoconverterresolution.LowVoltageDifferentialSignaling(LVDS)StandarddefinedinANSI/TIA/EIA-644andIEEE1596.3MMaximumConversionRateTheencoderateatwhichparametrictestingisperformed.MinimumConversionRateTheencoderateatwhichtheSNRofthelowestanalogsignalfrequencydropsbynomorethan3dBbelowtheguaranteedlimit.MonotonicityAconverterismonotoniciftheoutputeitherincreasesorremainsconstantastheinputincreases.MostSignificantBit(MSB)Theleft-mostbitinadataconvertercode.NNoiseWhereZistheinputimpedance,FSisthefullscaleofthedeviceforthefrequencyinquestion,SNRisthevaluefortheparticularinputlevelandSignalisthesignallevelwithintheADCreportedindBbelowfullscale.Thisvalueincludesboththermalandquantizationnoise.NyquistTheoryThistheorysaysthatifacontinuousbandwidth-limitedsignalcontainsnofrequencycomponentshigherthanfC,thentheoriginalsignalcanberecoveredwithoutdistortionifitissampledatarateofatleast2*fC.OPage4of7AnalogDevices:DataConverters:HighSpeedAnalog-to-DigitalConvertersGlossaryOffsetBinaryNaturalbinarycodeinwhichthecoderepresentsanalogvaluesbetween-FSand+FS.Thecode0000…0000correspondsto-FS.OffsetErrorOffseterroristhedifferencebetweenthemeasuredandidea