Holtek HT66F30 - LVD Operation

Rev. 2.50 226 June 22, 2017 Rev. 2.50 227 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
LVD Operation
TheLowVoltageDetectorfunctionoperatesbycomparingthepowersupplyvoltage,V
DD
,witha
pre-speciedvoltagelevelstoredintheLVDCregister.Thishasarangeofbetween2.0Vand4.4V.
Whenthepowersupplyvoltage,V
DD
,fallsbelowthispre-determinedvalue,theLVDObitwillbe
sethighindicatingalowpowersupplyvoltagecondition.TheLowVoltageDetectorfunctionis
suppliedbyareferencevoltagewhichwillbeautomaticallyenabled.Whenthedeviceispowered
downthelowvoltagedetectorwillremainactiveiftheLVDENbitishigh.AfterenablingtheLow
VoltageDetector,atimedelayt
LVDS
shouldbeallowedforthecircuitrytostabilisebeforereadingthe
LVDObit.NotealsothatastheV
DD
voltagemayriseandfallratherslowly,atthevoltagenearsthat
ofV
LVD
,theremaybemultiplebitLVDOtransitions.







LVD Operation
TheLowVoltageDetectoralsohasitsowninterruptwhichiscontainedwithinoneofthe
Multi-functioninterrupts,providinganalternativemeansoflowvoltagedetection,inadditionto
pollingtheLVDObit.Theinterruptwillonlybegeneratedafteradelayoft
LVD
aftertheLVDObit
hasbeensethighbyalowvoltagecondition.WhenthedeviceispowereddowntheLowVoltage
DetectorwillremainactiveiftheLVDENbitishigh.Inthiscase,theLVFinterruptrequestag
willbeset,causinganinterrupttobegeneratedifV
DD
fallsbelowthepresetLVDvoltage.Thiswill
causethedevicetowake-upfromtheSLEEPorIDLEMode,howeveriftheLowVoltageDetector
wakeupfunctionisnotrequiredthentheLVFagshouldberstsethighbeforethedeviceenters
theSLEEPorIDLEMode.