HT45F5Q datasheet(47/114 Pages) HOLTEK

47 / 114 page

Rev. 1.10

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HT45F5Q

Charger Flash MCU

HT45F5Q

Charger Flash MCU

RES Pin Reset

AlthoughthemicrocontrollerhasaninternalRCresetfunction,iftheVDDpowersupplyrisetime

isnotfastenoughordoesnotstabilisequicklyatpower-on,theinternalresetfunctionmaybe

incapableofprovidingproperresetoperation.Forthisreasonitisrecommendedthatanexternal

RCnetworkisconnectedtotheRESpin,whoseadditionaltimedelaywillensurethattheRESpin

remainslowforanextendedperiodtoallowthepowersupplytostabilise.Duringthistimedelay,

normaloperationofthemicrocontrollerwillbeinhibited.AftertheRESlinereachesacertain

voltagevalue,theresetdelaytimetRSTDisinvokedtoprovideanextradelaytimeafterwhichthe

microcontrollerwillbeginnormaloperation.TheabbreviationSSTinthefiguresstandsforSystem

Start-upTimer.

FormostapplicationsaresistorconnectedbetweenVDDandtheRESpinandacapacitorconnected

betweenVSSandtheRESpinwillprovideasuitableexternalresetcircuit.Anywiringconnected

totheRESpinshouldbekeptasshortaspossibletominimizeanystraynoiseinterference.For

applicationsthatoperatewithinanenvironmentwheremorenoiseispresenttheEnhancedReset

Circuitshownisrecommended.

RE S

0. 1~ 1 m F

10 k W ~

100k W

VD D

VSS

0. 01 m F* *

V DD

1N 4148 *

30 0 W *

Note:“*”ItisrecommendedthatthiscomponentisaddedforaddedESDprotection

“**”Itisrecommendedthatthiscomponentisaddedinenvironmentswherepowerlinenoise

issignificant

External RES Circuit

MoreinformationregardingexternalresetcircuitsislocatedinApplicationNoteHA0075Eonthe

Holtekwebsite.

PullingtheRESPinlowusingexternalhardwarewillalsoexecuteadevicereset.Inthiscase,asin

thecaseofotherresets,theProgramCounterwillresettozeroandprogramexecutioninitiatedfrom

thispoint.

RE S

In te r nal R es et

0. 9 V DD

0. 4 V DD

t RS TD + t SST

Note:tRSTDispower-ondelay,typicaltime=16.7ms

RES Reset Timing Chart

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