Holtek HT66F20 - Comparators; Comparator Operation

Rev. 2.50 180 June 22, 2017 Rev. 2.50 181 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
Comparators
Twoindependentanalogcomparatorsarecontainedwithinthesedevices.Thesefunctionsoffer
exibilityviatheirregistercontrolledfeaturessuchaspower-down,polarityselect,hysteresisetc.
InsharingtheirpinswithnormalI/OpinsthecomparatorsdonotwastepreciousI/Opinsifthere
functionsareotherwiseunused.

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  


Comparator
Comparator Operation
Thedevicecontainstwocomparatorfunctionswhichareusedtocomparetwoanalogvoltages
andprovideanoutputbasedontheirdifference.Fullcontroloverthetwointernalcomparators
isprovidedviatwocontrolregisters,CP0CandCP1C,oneassignedtoeachcomparator.The
comparatoroutputisrecordedviaabitintheirrespectivecontrolregister,butcanalsobetransferred
outontoasharedI/Opin.Additionalcomparatorfunctionsinclude,outputpolarity,hysteresis
functionsandpowerdowncontrol.
Anypull-highresistorsconnectedtothesharedcomparatorinputpinswillbeautomatically
disconnectedwhenthecomparatorisenabled.Asthecomparatorinputsapproachtheirswitching
level,somespuriousoutputsignalsmaybegeneratedonthecomparatoroutputduetotheslow
risingorfallingnatureoftheinputsignals.Thiscanbeminimisedbyselectingthehysteresis
functionwillapplyasmallamountofpositivefeedbacktothecomparator.Ideallythecomparator
shouldswitchatthepointwherethepositiveandnegativeinputssignalsareatthesamevoltage
level,however,unavoidableinputoffsetsintroducesomeuncertaintieshere.Thehysteresisfunction,
ifenabled,alsoincreasestheswitchingoffsetvalue.