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