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HT45F5R Datasheet(PDF) 46 Page - Holtek Semiconductor Inc |
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HT45F5R Datasheet(HTML) 46 Page - Holtek Semiconductor Inc |
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46 / 138 page ![]() Rev. 1.10 4� De�e��e� 1�� �01� Rev. 1.10 47 De�e��e� 1�� �01� HT45F5R Charger ASSP Flash MCU HT45F5R Charger ASSP Flash MCU Standby Current Considerations AsthemainreasonforenteringtheSLEEPorIDLEModeistokeepthecurrentconsumptionofthe devicetoaslowavalueaspossible,perhapsonlyintheorderofseveralmicro-ampsexceptinthe IDLE1andIDLE2Mode,thereareotherconsiderationswhichmustalsobetakenintoaccountby thecircuitdesignerifthepowerconsumptionistobeminimised.Specialattentionmustbemade totheI/Opinsonthedevice.Allhigh-impedanceinputpinsmustbeconnectedtoeitherafixed highorlowlevelasanyfloatinginputpinscouldcreateinternaloscillationsandresultinincreased currentconsumption.Thisalsoappliestodeviceswhichhavedifferentpackagetypes,astheremay beunbonbedpins.Thesemusteitherbesetupasoutputsorifsetupasinputsmusthavepull-high resistorsconnected. Caremustalsobetakenwiththeloads,whichareconnectedtoI/Opins,whicharesetupasoutputs. Theseshouldbeplacedinaconditioninwhichminimumcurrentisdrawnorconnectedonlyto externalcircuitsthatdonotdrawcurrent,suchasotherCMOSinputs.Alsonotethatadditional standbycurrentwillalsoberequirediftheLIRCoscillatorhasenabled. IntheIDLE1andIDLE2Modethehighspeedoscillatorison,iftheperipheralfunctionclock sourceisderivedfromthehighspeedoscillator,theadditionalstandbycurrentwillalsobeperhaps intheorderofseveralhundredmicro-amps. Wake-up TominimisepowerconsumptionthedevicecanentertheSLEEPorIDLE0~2Mode,wherethe systemclocksourcetotheCPUwillbestopped.Howeverwhenthedeviceiswokenupagain,it cantakeaconsiderabletimefortheoriginalsystemoscillatortorestart,stabiliseandallownormal operationtoresume. AfterthesystementerstheSLEEPorIDLEMode,itcanbewokenupfromoneofvarioussources listedasfollows: • AnexternalfallingedgeonPortA • Asysteminterrupt • AWDToverflow Whenthedeviceexecutesthe"HALT"instruction,thePDFflagwillbesetto1.ThePDFflagwill beclearedto0ifthedeviceexperiencesasystempower-uporexecutestheclearWatchdogTimer instruction.IfthesystemiswokenupbyaWDToverflow,aWatchdogTimerresetwillbeinitiated andtheTOflagwillbesetto1.TheTOflagissetifaWDTtime-outoccursandcausesawake-up thatonlyresetstheProgramCounterandStackPointer,otherflagsremainintheiroriginalstatus. EachpinonPortAcanbesetupusingthePAWUregistertopermitanegativetransitiononthepin towakeupthesystem.WhenaPortApinwake-upoccurs,theprogramwillresumeexecutionat theinstructionfollowingthe"HALT"instruction.Ifthesystemiswokenupbyaninterrupt,then twopossiblesituationsmayoccur.Thefirstiswheretherelatedinterruptisdisabledortheinterrupt isenabledbutthestackisfull,inwhichcasetheprogramwillresumeexecutionattheinstruction followingthe"HALT"instruction.Inthissituation,theinterruptwhichwokeupthedevicewillnot beimmediatelyserviced,butwillratherbeservicedlaterwhentherelatedinterruptisfinallyenabled orwhenastacklevelbecomesfree.Theothersituationiswheretherelatedinterruptisenabledand thestackisnotfull,inwhichcasetheregularinterruptresponsetakesplace.Ifaninterruptrequest flagissethighbeforeenteringtheSLEEPorIDLEMode,thewake-upfunctionoftherelated interruptwillbedisabled. |
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