ADC的各项参数定义

ADC的各项参数定义：ParameterDefinitionsIntegralNonlinearity(INL)Integralnonlinearityisthedeviationofthevaluesonanactualtransferfunctionfromastraightline.FortheMAX1209,thisstraightlineisbetweentheendpointsofthetransferfunction,onceoffsetandgainerrorshavebeennullified.INLdeviationsaremeasuredateverystepofthetransferfunctionandtheworst-casedeviationisreportedintheElectricalCharacteristicstable.DifferentialNonlinearity(DNL)Differentialnonlinearityisthedifferencebetweenanactualstepwidthandtheidealvalueof1LSB.ADNLerrorspecificationoflessthan1LSBguaranteesnomissingcodesandamonotonictransferfunction.FortheMAX1209,DNLdeviationsaremeasuredateverystepofthetransferfunctionandtheworst-casedeviationisreportedintheElectricalCharacteristicstable.OffsetErrorOffseterrorisafigureofmeritthatindicateshowwelltheactualtransferfunctionmatchestheidealtransferfunctionatasinglepoint.IdeallythemidscaleMAX1209transitionoccursat0.5LSBabovemidscale.Theoffseterroristheamountofdeviationbetweenthemeasuredmidscaletransitionpointandtheidealmidscaletransitionpoint.GainErrorGainerrorisafigureofmeritthatindicateshowwelltheslopeoftheactualtransferfunctionmatchestheslopeoftheidealtransferfunction.Theslopeoftheactualtransferfunctionismeasuredbetweentwodatapoints:positivefullscaleandnegativefullscale.Ideally,thepositivefull-scaleMAX1209transitionoccursat1.5LSBsbelowpositivefullscale,andthenegativefullscaletransitionoccursat0.5LSBabovenegativefullscale.Thegainerroristhedifferenceofthemeasuredtransitionpointsminusthedifferenceoftheidealtransitionpoints.Small-SignalNoiseFloor(SSNF)Small-signalnoiseflooristheintegratednoiseanddistortionpowerintheNyquistbandforsmall-signalinputs.TheDCoffsetisexcludedfromthisnoisecalculation.Forthisconverter,asmallsignalisdefinedasasingletonewithanamplitudelessthan-35dBFS.Thisparametercapturesthethermalandquantizationnoisecharacteristicsoftheconverterandcanbeusedtohelpcalculatetheoverallnoisefigureofareceivechannel.Goto(SNR)Forawaveform.perfectlyreconstructedfromdigitalsamples,thetheoreticalmaximumSNRistheratioofthefull-scaleanaloginput(RMSvalue)totheRMSquantizationerror(residualerror).Theideal,theoreticalminimumanalog-to-digitalnoiseiscausedbyquantizationerroronlyandresultsdirectlyfromtheADC’sresolution(Nbits):SNR[max]=6.02×N+1.76Inreality,thereareothernoisesourcesbesidesquantizationnoise:thermalnoise,referencenoise,clockjitter,etc.SNRiscomputedbytakingtheratiooftheRMSsignaltotheRMSnoise.RMSnoiseincludesallspectralcomponentstotheNyquistfrequencyexcludingthefundamental,thefirstsixharmonics(HD2–HD7),andtheDCoffset.Signal-to-NoisePlusDistortion(SINAD)SINADiscomputedbytakingtheratiooftheRMSsignaltotheRMSnoiseplusdistortion.RMSnoiseplusdistortionincludesallspectralcomponentstotheNyquistfrequencyexcludingthefundamentalandtheDCoffset.EffectiveNumberofBits(ENOB)ENOBspecifiesthedynamicperformanceofanADCataspecificinputfrequencyandsamplingrate.AnidealADC’serrorconsistsofquantizationnoiseonly.ENOBforafull-scalesinusoidalinputwaveform.iscomputedfrom:（SINAD-1.76）/6.02Single-ToneSpurious-FreeDynamicRange(SFDR)SFDRistheratioexpressedindecibelsoftheRMSamplitudeofthefundamental(maximumsignalcomponent)totheRMSamplitudeofthenext-largestspuriouscomponent,excludingDCoffset.TotalHarmonicDistortion(THD)THDistheratiooftheRMSsumofthefirstsixharmonicsoftheinputsignaltothefundamentalitself.Thisisexpressedas:whereV1isthefundamentalamplitude,andV2throughV7aretheamplitudesofthe2nd-through7th-orderharmonics(HD2-HD7).IntermodulationDistortion(IMD)IMDistheratiooftheRMSsumoftheintermodulationproductstotheRMSsumofthetwofundamentalinputtones.Thisisexpressedas:Thefundamentalinputtoneamplitudes(V1andV2)areat-7dBFS.Fourteenintermodulationproducts(VIM_)areusedintheMAX1209IMDcalculation.Theintermodulationproductsaretheamplitudesoftheoutputspectrumatthefollowingfrequencies,wherefIN1andfIN2arethefundamentalinputtonefrequencies:?Second-orderintermodulationproducts:fIN1+fIN2,fIN2-fIN1?Third-orderintermodulationproducts:2xfIN1-fIN2,2xfIN2-fIN1,2xfIN1+fIN2,2xfIN2+fIN1?Fourth-orderintermodulationproducts:3xfIN1-fIN2,3xfIN2-fIN1,3xfIN1+fIN2,3xfIN2+fIN1?Fifth-orderintermodulationproducts:3xfIN1-2xfIN2,3xfIN2-2xfIN1,3xfIN1+2xfIN2,3xfIN2+2xfIN1Third-OrderIntermodulation(IM3)IM3isthetotalpowerofthethird-orderintermodulationproductstotheNyquistfrequencyrelativetothetotalinputpowerofthetwoinputtonesfIN1andfIN2.Theindividualinputtonelevelsareat-7dBFS.Thethirdorderintermodulationproductsare2xfIN1-fIN2,2xfIN2-fIN1,2xfIN1+fIN2,2xfIN2+fIN1.Two-ToneSpurious-FreeDynamicRange(SFDRTT)SFDRTTrepresentstheratio,expressedindecibels,oftheRMSamplitudeofeitherinputtonetotheRMSamplitudeofthenext-largestspuriouscomponentinthespectrum,excludingDCoffset.ThisspuriouscomponentcanoccuranywhereinthespectrumuptoNyquistandisusuallyanintermodulationproductoraharmonic.Full-PowerBandwidthAlarge-0.5dBFSanaloginputsignalisappliedtoanADC,andtheinputfrequencyissweptuptothepointwheretheamplitudeofthedigitizedconversionresulthasde