Holtek BS82B12A-3 - LVD Ope�Ation

Rev. 1.20 146 January 23, 2015 Rev. 1.20 147 January 23, 2015
BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Key 8-Bit Flash MCU with LED/LCD Driver
BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Key 8-Bit Flash MCU with LED/LCD Driver
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2.7Vand4.0V.
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inSLEEP
modethelowvoltagedetectorwillbeautomaticallydisabledeven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.
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

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LVD Operation
TheLowVoltageDetectoralsohasitsowninterrupt,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.Inthiscase,theLVDF
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LVDFagshouldberstsethigh
beforethedeviceenterstheSLEEPorIDLEMode.