HT67F488 datasheet(145/171 Pages) HOLTEK

145 / 171 page

Rev. 1.60

145

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HT67F488/HT67F489

TinyPowerTM A/D Flash MCU with LCD & EEPROM

LVD Operation

TheLowVoltageDetectorfunctionoperatesbycomparingthepowersupplyvoltage,VDD,witha

pre-specifiedvoltagelevelstoredintheLVDCregister.Thishasarangeofbetween2.0Vand4.0V.

Whenthepowersupplyvoltage,VDD,fallsbelowthispre-determinedvalue,theLVDObitwillbe

sethighindicatingalowpowersupplyvoltagecondition.TheLowVoltageDetectorfunctionis

suppliedbyareferencevoltagewhichwillbeautomaticallyenabled.Whenthedeviceispowered

downthelowvoltagedetectorwillremainactiveiftheLVDENbitishigh.AfterenablingtheLow

VoltageDetector,atimedelaytLVDSshouldbeallowedforthecircuitrytostabilisebeforereadingthe

LVDObit.NotealsothatastheVDDvoltagemayriseandfallratherslowly,atthevoltagenearsthat

ofVLVD,theremaybemultiplebitLVDOtransitions.

VD D

V LV D

LV DE N

LV DO

t LV DS

LVD Operation

TheLowVoltageDetectoralsohasitsowninterruptwhichiscontainedwithinoneoftheMulti-

functioninterrupts,providinganalternativemeansoflowvoltagedetection,inadditiontopolling

theLVDObit.TheinterruptwillonlybegeneratedafteradelayoftLVDaftertheLVDObithasbeen

sethighbyalowvoltagecondition.WhenthedeviceispowereddowntheLowVoltageDetector

willremainactiveiftheLVDENbitishigh.Inthiscase,theLVFinterruptrequestflagwillbeset,

causinganinterrupttobegeneratedifVDDfallsbelowthepresetLVDvoltage.Thiswillcausethe

devicetowake-upfromtheSLEEPorIDLEMode,howeveriftheLowVoltageDetectorwakeup

functionisnotrequiredthentheLVFflagshouldbefirstsethighbeforethedeviceenterstheSLEEP

orIDLEMode.

WhenLVDfunctionisenabled,itisrecommencedtoclearLVDflagfirst,andthenenablesinterrupt

functiontoavoidmistakeaction.

HT67F488 Datasheet(PDF) 145 Page - Holtek Semiconductor Inc