Holtek HT66F0175 - External Crystal;Ceramic Oscillator - HXT

Rev. 1.50 42 August 28, 2017 Rev. 1.50 43 August 28, 2017
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HIRC
Prescaler
f
H
LXT
High Speed
Oscillator
Low Speed
Oscillator
f
H
/2
f
H
/16
f
H
/64
f
H
/8
f
H
/4
f
H
/32
HLCLK,
CKS2~CKS0
f
SYS
f
SUB
f
SUB
LIRC
HXT
f
H
High Speed Oscillator
Configuration Option
Low Speed Oscillator
Configuration Option
Fast Wake-up from IDLE
or SLEEP Mode Control
(for HXT only )
System Clock Congurations
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manufacturer’sspecication.
Foroscillatorstabilityandtominimisetheeffectsofnoiseandcrosstalk,itisimportanttoensure
thatthecrystalandanyassociatedresistorsandcapacitorsalongwithinterconnectinglinesareall
locatedasclosetotheMCUaspossible.




 
   
   
 



       
      
    
Crystal/Resonator Oscillator
HXT Oscillator C1 and C2 Values
Crystal Frequency C1 C2
12MHz 0 pF 0 pF
8MHz 0 pF 0 pF
4MHz 0 pF 0 pF
1MHz 100 pF 100 pF
Note: C1 and C2 values are for guidance only.
Crystal Recommended Capacitor Values