HT45F4M datasheet(92/138 Pages) HOLTEK

92 / 138 page

Rev. 1.10

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HT45F4M

Lithium Battery Backup Power ASSP MCU

HT45F4M

Lithium Battery Backup Power ASSP MCU

Controllingthepoweron/offfunctionoftheA/Dconvertercircuitryisimplementedusingthe

ADOFFbitintheADCR0register.ThisbitmustbezerotopowerontheA/Dconverter.Whenthe

ADOFFbitisclearedtozerotopowerontheA/Dconverterinternalcircuitryacertaindelay,as

indicatedinthetimingdiagram,mustbeallowedbeforeanA/Dconversionisinitiated.Evenifno

pinsareselectedforuseasA/DinputsbyclearingtheACE7~ACE0bitsintheACERLregisters,if

theADOFFbitiszerothensomepowerwillstillbeconsumed.Inpowerconsciousapplicationsit

isthereforerecommendedthattheADOFFissethightoreducepowerconsumptionwhentheA/D

converterfunctionisnotbeingused.

ThereferencevoltagesupplytotheA/DConvertercanbesuppliedfromeitherthepositivepowersupply

pin,VDD,orfromanexternalreferencesourcessuppliedonpinVREF.Thedesiredselectionismade

usingtheVREFSbit.AstheVREFpinispin-sharedwithotherfunctions,whentheVREFSbitisset

high,theVREFpinfunctionwillbeselectedandtheotherpinfunctionswillbedisabledautomatically.

A/D Input Pins

AlloftheA/Danaloginputpinsarepin-sharedwiththeI/OpinsonPortAaswellasother

functions.TheACE7~ACE0bitsintheACERLregisters,determinewhethertheinputpinsaresetup

asA/Dconverteranaloginputsorwhethertheyhaveotherfunctions.IftheACE7~ACE0bitsforits

correspondingpinissethighthenthepinwillbesetuptobeanA/Dconverterinputandtheoriginal

pinfunctionsdisabled.Inthisway,pinscanbechangedunderprogramcontroltochangetheir

functionbetweenA/Dinputsandotherfunctions.Allpull-highresistors,whicharesetupthrough

registerprogramming,willbeautomaticallydisconnectedifthepinsaresetupasA/Dinputs.Note

thatitisnotnecessarytofirstsetuptheA/DpinasaninputinthePACportcontrolregistertoenable

theA/DinputaswhentheACE7~ACE0bitsenableanA/Dinput,thestatusoftheportcontrol

registerwillbeoverridden.

TheA/Dconverterhasitsownreferencevoltagepin,VREF,howeverthereferencevoltagecan

alsobesuppliedfromthepowersupplypin,achoicewhichismadethroughtheVREFSbitinthe

ADCR1register.TheanaloginputvaluesmustnotbeallowedtoexceedthevalueofVREF.

PA 0/ AN 0 PA7 /A N7

1. 25V

VB GE N

Bu ff er

PA1 /V RE F

VD D

VR EF S

V RE F

12 -b i t A DC

Ba ndgap

Re fe r enc e

Vo lt ag e

In put V ol ta g e

AC S4 ~A CS 0

AN 8

A/D Input Structure

HT45F4M Datasheet(PDF) 92 Page - Holtek Semiconductor Inc

HT45F4M Datasheet(HTML) 92 Page - Holtek Semiconductor Inc

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