HT45F4M datasheet(32/138 Pages) HOLTEK

32 / 138 page

Rev. 1.10

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HT45F4M

Lithium Battery Backup Power ASSP MCU

HT45F4M

Lithium Battery Backup Power ASSP MCU

Internal RC Oscillator – HIRC

TheinternalRCoscillatorisafullyintegratedsystemoscillatorrequiringnoexternalcomponents.

TheinternalRCoscillatorhasseveralfrequenciesofeither30MHzbyoption.Devicetrimming

duringthemanufacturingprocessandtheinclusionofinternalfrequencycompensationcircuitsare

usedtoensurethattheinfluenceofthepowersupplyvoltage,temperatureandprocessvariationson

theoscillationfrequencyareminimised.Notethatifthisinternalsystemclockoptionisselected,as

itrequiresnoexternalpinsforitsoperation.

Internal 32kHz Oscillator – LIRC

TheInternal32kHzSystemOscillatoristhelowfrequencyoscillator.Itisafullyintegrated

RCoscillatorwithatypicalfrequencyof32kHzat5V,requiringnoexternalcomponentsforits

implementation.Devicetrimmingduringthemanufacturingprocessandtheinclusionofinternal

frequencycompensationcircuitsareusedtoensurethattheinfluenceofthepowersupplyvoltage,

temperatureandprocessvariationsontheoscillationfrequencyareminimised.

Operating Modes and System Clocks

Presentdayapplicationsrequirethattheirmicrocontrollershavehighperformancebutoftenstill

demandthattheyconsumeaslittlepoweraspossible,conflictingrequirementsthatareespecially

trueinbatterypoweredportableapplications.Thefastclocksrequiredforhighperformancewill

bytheirnatureincreasecurrentconsumptionandofcoursevice-versa,lowerspeedclocksreduce

currentconsumption.AsHoltekhasprovidedthisdevicewithbothhighandlowspeedclock

sourcesandthemeanstoswitchbetweenthemdynamically,theusercanoptimisetheoperationof

theirmicrocontrollertoachievethebestperformance/powerratio.

System Clocks

ThedevicehasmanydifferentclocksourcesforboththeCPUandperipheralfunctionoperation.

Byprovidingtheuserwithawiderangeofclockoptionsusingconfigurationoptionsandregister

programming,aclocksystemcanbeconfiguredtoobtainmaximumapplicationperformance.

Themainsystemclock,cancomefromeitherahighfrequency,fH,orlowfrequency,fSUB,source,

andisselectedusingtheHLCLKbitandCKS2~CKS0bitsintheSMODregister.Thehighspeed

systemclockcanbesourcedfromtheHIRCoscillator.Thelowspeedsystemclocksourcecanbe

sourcedfromtheLIRCoscillator.Theotherchoice,whichisadividedversionofthehighspeed

systemoscillatorhasarangeoffH/2~fH/64.

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