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ID:15908763
大小:195.50 KB
页数:16页
时间:2018-08-06
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1、AN606LowPowerDesignUsingPICmicro™MicrocontrollersFIGURE1:USINGANEXTERNALAuthor:RodgerRicheyRESISTORTOLOWERPOWERMicrochipTechnologyInc.INRCMODEVDDINTRODUCTIONPowerconsumptionisanimportantelementinVDDI/OpinRdesigningasystem,particularlyintoday’sbatteryR1poweredworld.ThePICmi
2、crofamilyofdeviceshasMCLROSC1beendesignedtogivetheuseralow-cost,low-power,VSSCandhigh-performancesolutiontothisproblem.Fortheapplicationtooperateatthelowestpossiblepower,thePICmicrodesignermustensurethatthePICmicrodevicesareproperlyconfigured.ThisapplicationnotedescribesExt
3、ernaleventscanbeusedtocontrolthepowertosomedesigntechniquestolowercurrentconsumption,PICmicrodevices.Forthesecases,theWatchdogsomebatterydesignconsiderations,andsuggestionsTimercanbedisabledtofurtherreducecurrenttoassistthedesignerinresolvingpowerconsumptionconsumption.Fig
4、ure2showsanexamplecircuitthatproblems.usesanexternaleventtolatchpoweronforthePICmi-crodevice.OncethedevicehasfinishedexecutingDESIGNTECHNIQUEScode,itdisablespowerbyresettingthelatch.Thelatch-ingcircuitusesalow-power4000seriesCMOSquadManytechniquesareusedtoreducepowerchipwhi
5、chconsumesatypicalof10mAofcurrent.TheconsumptioninthePICmicrodevices.Themostmeasuredvalueofcurrentconsumptionforthecom-commonlyusedmethodsareSLEEPModeandexter-pletecircuitwiththePICmicropowered-downwas1nA.nalevents.ThesemodesarethebestwaytoreduceIPDCurrentconsumptionforaPI
6、CmicroinSLEEPModeisinasystem.ThePICmicrodevicecanperiodicallytypically1mA.wake-upfromSleepusingtheWatchdogTimerorexter-nalinterrupt,executecodeandthengobackintoFIGURE2:EXTERNALEVENTPOWERSLEEPMode.InSLEEPModetheoscillatorisshutoff,CONTROLCIRCUITwhichcausesthePICmicrodevicet
7、oconsumeverylittlecurrent.TypicalIPDcurrentinmostPICmicrodevicesisontheorderofafewmicroamps.IncaseswherethePICmicrousesanRCoscillatorbutV+cannotuseSLEEPMode,anothertechniqueisusedtolowerpowerconsumption.AnI/Opincanremoveapar-1/4CD4011allelresistancefromtheoscillatorresisto
8、rwhilewaitingforaneventtooccur.ThiswouldslowdowntheinternalV+clockfrequency,byincreasingt
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