标签: 互补驱动

LightEmittingDiodes,orLED's,arediscretecompo-nentsabletoproducelightwhenacurrentpassesthroughthem.MostmicrocontrollerdesignsuseoneormoreLED's.ThisapplicationhighlightstheutilityofdrivingmultipleLED'swithaminimumnumberofI/Opins.Typically,eachI/OdrivesorsourcesasingleLED.Todrivemorethanone,ahighI/Ocountisrequired.InordertoreduceI/Orequirements,LED'saremulti-plexedinamatrix(asfoundonakeyboard).Thecom-plementaryLEDdrivemethodproposestoimplementevenmoreLEDswhileusingfewerI/O.LEDsarepolarizedandcanonlyoperatewhencurrentflowsfromanodetocathode(unlikeaswitch).Wecanthereforetakeadvantageofthisfact.Table1showsthenumberofpossibleLEDswithrespecttothenumberofI/Opinsrequired.Fifty-sixLEDscanbedrivenusingonly8pins.TheonlydrawbackisthatonlyoneLEDcanbedrivenatatime.MTB029ComplementaryLEDDriveTHEORYOFOPERATIONAuthor:Jean-ClaudeRebicPioneer-StandardSomemicrocontrollersavailabletodaycansinkhighcurrent,whileothersofferalimitednumberofpinstosourcehighcurrent.MicrochipmicrocontrollershaveaINTRODUCTIONveryexiblepinstructure.Whenapinisconguredasaninput,th……