HT69F240 datasheet(35/172 Pages) HOLTEK

35 / 172 page

Rev. 1.20

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Rev. 1.20

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HT69F240

I/O 8-Bit Flash MCU with LED/LCD Driver

HT69F240

I/O 8-Bit Flash MCU with LED/LCD Driver

LXT Oscillator Low Power Function

TheLXToscillatorcanfunctioninoneoftwomodes,theQuickStartModeandtheLowPower

Mode.ThemodeselectionisexecutedusingtheLXTLPbitintheTBCregister.

LXTLP Bit

LXT Mode

Qui�k Sta�t

Low-powe�

AfterpowerontheLXTLPbitwillbeautomaticallyclearedtozeroensuringthattheLXToscillator

isintheQuickStartoperatingmode.IntheQuickStartModetheLXToscillatorwillpowerup

andstabilisequickly.However,aftertheLXToscillatorhasfullypoweredupitcanbeplaced

intotheLow-powermodebysettingtheLXTLPbithigh.Theoscillatorwillcontinuetorunbut

withreducedcurrentconsumption,asthehighercurrentconsumptionisonlyrequiredduringthe

LXToscillatorstart-up.Inpowersensitiveapplications,suchasbatteryapplications,wherepower

consumptionmustbekepttoaminimum,itisthereforerecommendedthattheapplicationprogram

setstheLXTLPbithighabout2secondsafterpower-on.

Itshouldbenotedthat,nomatterwhatconditiontheLXTLPbitissetto,theLXToscillatorwill

alwaysfunctionnormally,theonlydifferenceisthatitwilltakemoretimetostartupifinthe

Low-powermode.

Internal 32kHz Oscillator – LIRC

TheInternal32kHzSystemOscillatorisoneofthelowfrequencyoscillatorchoices,whichis

selectedviaconfigurationoption.ItisafullyintegratedRCoscillatorwithatypicalfrequencyof

32kHzat5V,requiringnoexternalcomponentsforitsimplementation.Devicetrimmingduring

themanufacturingprocessandtheinclusionofinternalfrequencycompensationcircuitsareused

toensurethattheinfluenceofthepowersupplyvoltage,temperatureandprocessvariationsonthe

oscillationfrequencyareminimised.Asaresult,atapowersupplyof5Vandatatemperatureof

25°Cdegrees,thefixedoscillationfrequencyof32kHzwillhaveatolerancewithin10%.

Supplementary Oscillators

Thelowspeedoscillators,inadditiontoprovidingasystemclocksourcearealsousedtoprovide

aclocksourcetotwootherdevicefunctions.ThesearetheWatchdogTimerandtheTimeBase

Interrupts.

HT69F240 Datasheet(PDF) 35 Page - Holtek Semiconductor Inc