数字集成技术的高速双斜率A D转换
Byusinglow-costmicroprocessorsandaprogram-controlled
numerical-integrationtechnique,youcanachievegoodnoise
rejectionandtakefulladvantageofthehigherspeedsofferedby
recentlydevelopeddual-slopeA/DconverterssuchastheTC7109.
Thisandsimilarconvertersovercomethespeedlimitations
imposedbylogic-gateandanalogcomparatordelaysinearlier
dual-slopedevices,andthemodernunitscanoperateatratesas
highas30to100samples/sec.Nevertheless,operatingthemat
theirmaximumconversionratesoftenmakesitdifficultorimpos-
sibletoachievethehighnormal-modeline-frequencyrejectionthat
dual-slopeA/Dconvertersinherentlyofferatslowerconversion
rates.Thus,noiseconsiderationshaveoftenprecludeduseof
theseconvertersattheirratedspeeds—especiallyinindustrial
environments,whereline-frequencyandotherlow-frequencynoise
componentscanbeaparticularproblem.AN788Numerical-IntegrationTechniquesSpeedDual-SlopeA/DConversionTheintegratingA/DconverterintegratesthesignalonlyinacertainAuthor:GaryGrandboisandWesFreeman,timewindow,asFigure1bshows.ThislimitedintegrationperiodMicrochipTechnology,Inc.resultsinnormal-modenoiserejectiononlywhentheintegration
