HT69F360 datasheet(62/235 Pages) HOLTEK

62 / 235 page

Rev. 1.30

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Rev. 1.30

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HT69F340/HT69F350/HT69F360

TinyPowerTM I/O Flash MCU with LCD & EEPROM

HT69F340/HT69F350/HT69F360

TinyPowerTM I/O Flash MCU with LCD & EEPROM

External 32.768kHz Crystal Oscillator – LXT

TheExternal32.768kHzCrystalSystemOscillatorisoneofthelowfrequencyoscillatorchoices,

whichisselectedbyFSSbitandenabledbyLXTENbit.Thisclocksourcehasafixedfrequency

of32.768kHzandrequiresa32.768kHzcrystaltobeconnectedbetweenpinsXT1andXT2.The

externalresistorandcapacitorcomponentsconnectedtothe32.768kHzcrystalarenecessaryto

provideoscillation.Forapplicationswhereprecisefrequenciesareessential,thesecomponentsmay

berequiredtoprovidefrequencycompensationduetodifferentcrystalmanufacturingtolerances.

AftertheLXToscillatorisenabledbysettingtheLXTENbitto1,thereisatimedelayassociated

withtheLXToscillatorwaitingforittostart-up.

WhenthemicrocontrollerenterstheSLEEPorIDLEMode,thesystemclockisswitchedofftostop

microcontrolleractivityandtoconservepower.However,inmanymicrocontrollerapplications

itmaybenecessarytokeeptheinternaltimersoperationalevenwhenthemicrocontrollerisin

theSLEEPorIDLEMode.Todothis,anotherclock,independentofthesystemclock,mustbe

provided.

However,forsomecrystals,toensureoscillationandaccuratefrequencygeneration,itisnecessary

toaddtwosmallvalueexternalcapacitors,C1andC2.TheexactvaluesofC1andC2should

beselectedinconsultationwiththecrystalorresonatormanufacturerspecification.Theexternal

parallelfeedbackresistor,Rp,isrequired.

Thepin-sharedsoftwarecontrolbitsdetermineiftheXT1/XT2pinsareusedfortheLXToscillator

orasI/Opins.

• IftheLXToscillatorisnotusedforanyclocksource,theXT1/XT2pinscanbeusedasnormalI/

Opins.

• IftheLXToscillatorisusedforanyclocksource,the32.768kHzcrystalshouldbeconnectedto

theXT1/XT2pins.

Foroscillatorstabilityandtominimisetheeffectsofnoiseandcrosstalk,itisimportanttoensure

thatthecrystalandanyassociatedresistorsandcapacitorsalongwithinterconnectinglinesareall

locatedasclosetotheMCUaspossible.

To i nt er na l

ci rc ui ts

In te rn al

O sc illa to r

Ci rc ui t

No te :1 . Rp , C1 a nd C2 a re r e qui re d.

2. A lt hough n ot s ho wn p in s ha ve a p ar as it ic c apac it anc e o f a ro u nd 7pF .

In te r nal R C

Os c illa to r

32 .7 68 kH z

XT 1

XT 2

External LXT Oscillator

LXT Oscillator C1 and C2 Values

Crystal Frequency

3�.7��kHz

10pF

�ote: 1. C1 and C� values a�e fo� guidance only.

�. RP=5MΩ~10MΩ is recommended.

32.768kHz Crystal Recommended Capacitor Values

HT69F360 データシート(PDF) 62 Page - Holtek Semiconductor Inc

HT69F360 データシート(HTML) 62 Page - Holtek Semiconductor Inc

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