ETIC 2230 Guia do Utilizador descarregar pdf (Página 32)

Rev. 1.10 32 November 14, 2014 Rev. 1.10 33 November 14, 2014

HT66FW2230

Wireless Charger A/D Flash 8-Bit MCU

External Crystal/ Ceramic Oscillator – HXT

TheExternalCrystal/CeramicSystemOscillatorisoneofthehighfrequencyoscillatorchoices,

whichisselectedviaregisters.Formostcrystaloscillatorcongurations,thesimpleconnectionof

acrystalacrossOSC1andOSC2willcreatethenecessaryphaseshiftandfeedbackforoscillation,

withoutrequiringexternalcapacitors.However,forsomecrystaltypesandfrequencies,toensure

oscillation,itmaybenecessarytoaddtwosmallvaluecapacitors,C1andC2.Usingaceramic

resonatorwillusuallyrequiretwosmallvaluecapacitors,C1andC2,tobeconnectedasshownfor

oscillationtooccur.ThevaluesofC1andC2shouldbeselectedinconsultationwiththecrystalor

resonatormanufacturer’sspecication.

Foroscillatorstabilityandtominimisetheeffectsofnoiseandcrosstalk,itisimportanttoensure

thatthecrystalandanyassociatedresistorsandcapacitorsalongwithinterconnectinglinesareall

locatedasclosetotheMCUaspossible.

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          

       

    

Crystal/Resonator Oscillator – HXT

Internal RC Oscillator – HIRC

TheinternalRCoscillatorisafullyintegratedsystemoscillatorrequiringnoexternalcomponents.

TheinternalRCoscillatorhasafixedfrequencyof20MHz.Devicetrimmingduringthe

manufacturingprocessandtheinclusionofinternalfrequencycompensationcircuitsareusedto

ensurethattheinuenceofthepowersupplyvoltage,temperatureandprocessvariationsonthe

oscillationfrequencyareminimised.Notethatifthisinternalsystemclockisselected,asitrequires

noexternalpinsforitsoperation.

Internal 32kHz Oscillator – LIRC

TheInternal32kHzSystemOscillatoristhelowfrequencyoscillator.Itisafullyintegrated

RCoscillatorwithatypicalfrequencyof32kHzat5V,requiringnoexternalcomponentsforits

implementation.Devicetrimmingduringthemanufacturingprocessandtheinclusionofinternal

frequencycompensationcircuitsareusedtoensurethattheinuenceofthepowersupplyvoltage,

temperatureandprocessvariationsontheoscillationfrequencyareminimised.

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