Holtek HT66F0175 - Internal 3�Khz Oscillator - LIRC; S�Pplementary Oscillators

Rev. 1.50 44 August 28, 2017 Rev. 1.50 45 August 28, 2017
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
LXT Oscillator C1 and C2 Values
Crystal Frequency C1 C2
32.768kHz 10pF 10pF
Note
: 1. C1 and C2 values are for guidance only.
2. R
P
=5M
Ω
~10M
Ω
is recommended.
32.768kHz Crystal Recommended Capacitor Values
LXT Oscillator Low Power Function
TheLXToscillatorcanfunctioninoneoftwomodes,theQuickStartModeandtheLowPower
Mode.ThemodeselectionisexecutedusingtheLXTLPbitintheTBCregister.
LXTLP LXT Operating Mode
0 Quick Start
1 Low-Power
Afterpoweron,theLXTLPbitwillbeautomaticallyclearedtozeroensuringthattheLXToscillator
isintheQuickStartoperatingmode.IntheQuickStartModetheLXToscillatorwillpowerup
andstabilisequickly.However,aftertheLXToscillatorhasfullypoweredupitcanbeplaced
intotheLow-powermodebysettingtheLXTLPbithigh.Theoscillatorwillcontinuetorunbut
withreducedcurrentconsumption,asthehighercurrentconsumptionisonlyrequiredduringthe
LXToscillatorstart-up.Inpowersensitiveapplications,suchasbatteryapplications,wherepower
consumptionmustbekepttoaminimum,itisthereforerecommendedthattheapplicationprogram
setstheLXTLPbithighabout2secondsafterpower-on.Itshouldbenotedthat,nomatterwhat
conditiontheLXTLPbitissetto,theLXToscillatorwillalwaysfunctionnormallyandtheonly
differenceisthatitwilltakemoretimetostartupifintheLow-powermode.
Internal 32kHz Oscillator – LIRC
TheInternal32kHzSystemOscillatorisoneofthelowfrequencyoscillatorchoices,whichis
selectedviacongurationoption.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.Asaresult,atapowersupplyof5Vandatatemperatureof
25°Cdegrees,thexedoscillationfrequencyof32kHzwillhaveatolerancewithin10%.
Supplementary Oscillators
Thelowspeedoscillators,inadditiontoprovidingasystemclocksourcearealsousedtoprovide
aclocksourcetotwootherdevicefunctions.ThesearetheWatchdogTimerandtheTimeBase
Interrupts.