BQ3285LDSS;中文规格书,Datasheet资料

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Features

®ACPI-compliantday-of-monthalarm

®Directclock/calendarreplace-mentforIBM®AT-compatible

computersandotherapplications

®2.7–5.5Voperation(bq3285LD);4.5–5.5Voperation(bq3285ED)

®242bytesofgeneralnonvolatilestorage

®Dedicated32.768kHzoutputpin

®Systemwake-upcapability—alarminterruptoutputactivein

battery-backupmode

®Lessthan0.55µAloadunderbat-teryoperation

®SelectableIntelorMotorolabustiming

®24-pinplasticSSOPGeneralDescription

TheCMOSbq3285ED/LDisalow-

powermicroprocessorperipheralpro-

vidingatime-of-dayclockand100-

yearcalendarwithalarmfeatures

andbatteryoperation.Thearchitec-

tureisbasedonthebq3285/7RTC

withaddedfeatures:low-voltageop-

eration,32.768kHzoutput,128addi-

tionalbytesofCMOS,andaday-of-

monthalarmtobecompliantwith

theACPIRTCspecification.

A32.768kHzoutputisavailablefor

sustainingpower-managementac-

tivities.Thebq3285ED/LD32kHz

outputisalwaysonwheneverVCCis

valid.InVCCstandbymode,the

32kHzisactive,andthebq3285LD

typicallydraws100µAwhilethe

bq3285EDtypicallydraws300µA.

Wake-upcapabilityisprovidedby

analarminterrupt,whichisactive

inbattery-backupmode.Inbattery-

backupmode,currentdrainisless

than550nA.Thebq3285ED/LDwrite-protectsthe

clock,calendar,andstorageregisters

duringpowerfailure.Abackup

batterythenmaintainsdataandoper-

atestheclockandcalendar.

Thebq3285ED/LDisafullycom-

patiblereal-timeclockforIBMAT-

compatiblecomputersandotherap-

plications.Theonlyexternalcompo-

nentsarea32.768kHzcrystalanda

backupbattery.

Thebq3285EDisintendedforusein

5Vsystems.Thebq3285LDisin-

tendedforusein3Vsystems;the

bq3285LD,however,mayalsooper-

ateat5Vandthengointoa3V

power-downstate,write-protecting

asifina3Vsystem.

1Real-TimeClock(RTC)bq3285ED/LD

1

PN3285ED/LD.eps 24-Pin SSOP

23

4 5

6

7

824

2322

21

20

19

18

17

9

1016

15

11

1214

13VCC

32kEXTRAM

BCINT

RST

DS

VSSR/W

AS

CSMOT

X1X2

AD0AD1AD2AD3AD4AD5AD6

AD7VSSRCLPinConnectionsPinNames

July1997AD0–AD7Multiplexedaddress/

datainput/output

MOTBustypeselectinput

CSChipselectinput

ASAddressstrobeinput

DSDatastrobeinput

R/WRead/writeinput

INTInterruptrequestoutput

RSTResetinput32K32.768kHzoutput

EXTRAMExtendedRAMenable

RCLRAMclearinput

BC3Vbackupcellinput

X1–X2Crystalinputs

VCCPowersupply

VSSGround

http://oneic.com/BlockDiagram

PinDescriptions

MOTBustypeselectinput

MOTselectsbustimingforeitherMotorola

orIntelarchitecture.Thispinshouldbe

tiedtoVCCforMotorolatimingortoVSSfor

Inteltiming(seeTable1).Thesetting

shouldnotbechangedduringsystemopera-

tion.MOTisinternallypulledlowbya30K

Ωresistor.AD0–AD7Multiplexedaddress/data

input/output

Thebq3285ED/LDbuscycleconsistsoftwo

phases:theaddressphaseandthedata-

transferphase.Theaddressphasepre-

cedesthedata-transferphase.Duringthe

addressphase,anaddressplacedon

AD0–AD7andEXTRAMislatchedintothe

bq3285ED/LDonthefallingedgeoftheAS

signal.Duringthedata-transferphaseof

thebuscycle,theAD0–AD7pinsserveasa

bidirectionaldatabus.

ASAddressstrobeinput

ASservestodemultiplextheaddress/data

bus.ThefallingedgeofASlatchesthead-

dressonAD0–AD7andEXTRAM.Thisde-

multiplexingprocessisindependentoftheCSsignal.ForDIPandSOICpackages

withMOT=VSS,theASinputisprovideda

signalsimilartoALEinanIntel-basedsys-tem.

2bq3285ED/LDBus

TypeMOT

LevelDS

EquivalentR/W

EquivalentAS

Equivalent

MotorolaVCCDS,E,or

Φ2R/WAS

IntelVSSRD,

MEMR,or

I/ORWR,

MEMW,or

I/OWALETable1.BusSetup

BD328501.eps PBus I/Fµ

Power-FailControlStorage Registers(114 Bytes)User Buffer(14 Bytes)

VOUTClock/Calendar, Alarmand Control BytesTime-BaseOscillator

Control/StatusRegisters÷ 8÷ 64÷ 64

16 1 MUX:

InteruptGenerator

Control/CalendarUpdate

VCCDSAD0–AD7CSMOT32K

INTX1

X2

34

RST

R/W

AS

Storage Registers(128 Bytes)RCL

EXTRAM

WriteProtectCS

BC32KDriver

July1997

http://oneic.com/DSDatastrobeinput

WhenMOT=VCC,DScontrolsdatatrans-

ferduringabq3285ED/LDbuscycle.Dur-

ingareadcycle,thebq3285ED/LDdrives

thebusaftertherisingedgeonDS.During

awritecycle,thefallingedgeonDSisused

tolatchwritedataintothechip.

WhenMOT=VSS,theDSinputisprovided

asignalsimilartoRD,MEMR,orI/ORin

anIntel-basedsystem.Thefallingedgeon

DSisusedtoenabletheoutputsduringa

readcycle.R/WRead/writeinput

WhenMOT=VCC,thelevelonR/Widenti-

fiesthedirectionofdatatransfer.Ahigh

levelonR/Windicatesareadbuscycle,

whereasalowonthispinindicatesawrite

buscycle.

WhenMOT=VSS,R/Wisprovidedasignal

similartoWR,MEMW,orI/OWinanIntel-

basedsystem.TherisingedgeonR/W

latchesdataintothebq3285ED/LD.CSChipselectinputCSshouldbedrivenlowandheldstable

duringthedata-transferphaseofabuscy-

cleaccessingthebq3285ED/LD.INTInterruptrequestoutputINTisanopen-drainoutput.Thisallows

alarmINTtobevalidinbattery-backup

mode.Tousethisfeature,connectINT

througharesistortoapowersupplyother

thanVCC.INTisassertedlowwhenany

eventflagissetandthecorresponding

eventenablebitisalsoset.INTbecomes

high-impedancewheneverregisterCisread

(seetheControl/StatusRegisterssection).

32K32.768kHzoutput