HT45F3W datasheet(49/167 Pages) HOLTEK

49 / 167 page

Rev. 1.50

De�e��e� 01� �01�

Rev. 1.50

De�e��e� 01� �01�

HT45F3W

R-Type Blood Pressure Meter Flash MCU

HT45F3W

R-Type Blood Pressure Meter Flash MCU

LXT Oscillator Low Power Function

TheLXToscillatorcanfunctioninoneoftwomodes,theQuickStartModeandtheLowPower

Mode.ThemodeselectionisexecutedusingtheLXTLPbitintheTBCregister.

LXTLP Bit

LXT Mode

Qui�k Sta�t

Low-powe�

Afterpoweron,theLXTLPbitwillbeautomaticallyclearedtozeroensuringthattheLXToscillator

isintheQuickStartoperatingmode.IntheQuickStartModetheLXToscillatorwillpowerup

andstabilisequickly.However,aftertheLXToscillatorhasfullypoweredupitcanbeplaced

intotheLow-powermodebysettingtheLXTLPbithigh.Theoscillatorwillcontinuetorunbut

withreducedcurrentconsumption,asthehighercurrentconsumptionisonlyrequiredduringthe

LXToscillatorstart-up.Inpowersensitiveapplications,suchasbatteryapplications,wherepower

consumptionmustbekepttoaminimum,itisthereforerecommendedthattheapplicationprogram

setstheLXTLPbithighabout2secondsafterpower-on.

Itshouldbenotedthat,nomatterwhatconditiontheLXTLPbitissetto,theLXToscillatorwill

alwaysfunctionnormally,theonlydifferenceisthatitwilltakemoretimetostartupifintheLow-

powermode.

Internal 32kHz Oscillator – LIRC

TheInternal32kHzSystemOscillatorisoneofthelowfrequencyoscillatorchoices,whichis

selectedviaconfigurationoption.ItisafullyintegratedRCoscillatorwithatypicalfrequencyof

32kHzat5V,requiringnoexternalcomponentsforitsimplementation.Devicetrimmingduring

themanufacturingprocessandtheinclusionofinternalfrequencycompensationcircuitsareused

toensurethattheinfluenceofthepowersupplyvoltage,temperatureandprocessvariationsonthe

oscillationfrequencyareminimised.Asaresult,atapowersupplyof5Vandatatemperatureof

25°Cdegrees,thefixedoscillationfrequencyof32kHzwillhaveatolerancewithin10%.

Supplementary Oscillators

Thelowspeedoscillators,inadditiontoprovidingasystemclocksourcearealsousedtoprovidea

clocksourcetothreeotherdevicefunctions.ThesearetheWatchdogTimer,theLCDdriverandthe

TimeBaseInterrupts.

HT45F3W датащи(PDF) 49 Page - Holtek Semiconductor Inc