Holtek HT66F30 - External Crystal;Ceramic Oscillator - HXT

Rev. 2.50 52 June 22, 2017 Rev. 2.50 53 June 22, 2017
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
External Crystal/Ceramic Oscillator – HXT
TheExternalCrystal/CeramicSystemOscillatorisoneofthehighfrequencyoscillatorchoices,
whichisselectedviaconfigurationoption.Formostcrystaloscillatorconfigurations,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manufacturers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MCUaspossible.




 
   
   
 



       
      
    
Crystal/Resonator Oscillator – HXT
Crystal Oscillator C1 and C2 Values
Crystal Frequency C1 C2
12MHz 0pF 0pF
8MHz 0pF 0pF
4MHz 0pF 0pF
1MHz 100pF 100pF
Note:
C1 and C2 values are for guidance only.
Crystal Recommended Capacitor Values