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APPLICATIONINFORMATION
INTRODUCTIONTOExpressCard
ExpressCardPOWERREQUIREMENTS
ExpressCardPOWERSWITCHOPERATION
TPS2231
TPS2236
SLVS536B–JULY2004–REVISEDJANUARY2005
anexpresscardmoduleisanadd-incardwithaserialinterfacebasedonpciexpressand/oruniversalserial
总线(usb)科技.anexpresscardcomesintwoformfactorsdefinedasexpresscard|34or
expresscard|54.thedifference,asdefinedbythename,isthewidthofthemodule,34mmor54mm,
各自.hostsystemssupportingtheexpresscardmodulecansupporteithertheexpresscard|34or
expresscard|54orboth.
regardlessofwhichexpresscardmoduleisused,thepowerrequirementsasdefinedintheexpresscard
standardapplytobothonanindividualslotbasis.thehostsystemisrequiredtosupply3.3v,1.5v,andaux
toeachoftheexpresscardslots.不管怎样,thevoltageisonlyappliedafteranexpresscardisinsertedintothe
slot.
theexpresscardconnectorhastwopins,cppeandcpusb,thatareusedtosignalthehostwhenacardis
inserted.iftheexpresscardmoduleitselfconnectsthecppetoground,thelogiclowlevelonthatsignal
indicatestothehostthatacardsupportingpciexpresshasbeeninserted.ifcpusbisconnectedtoground,
thentheexpresscardmodulesupportstheusbinterface.ifbothpciexpressandusbaresupportedbythe
expresscardmodule,thenbothsignals,cppeandcpusb,mustbeconnectedtoground.
inadditiontothecardpresentsignals(cppeandcpusb),thehostsystemdetermineswhentoapplypowerto
theexpresscardmodulebasedonthestateofthesystem.thestateofthesystemisdefinedbythestateofthe
3.3v,1.5v,andauxinputvoltagerails.forthesakeofsimplicity,the3.3-vand1.5-vrailsaredefinedasthe
primaryvoltagerailsasopposetotheauxiliaryvoltagerail,aux.
theexpresscardpowerswitchresidesonthehost,anditsmainfunctionistocontrolwhentosendpowertothe
expresscardslot.theexpresscardpowerswitchmakesdecisionsbasedonthecardpresentinputsandonthe
stateofthehostsystemasdefinedbytheprimaryandauxiliaryvoltagerails.
thefollowingconditionsdefinetheoperationofthehostpowercontroller:
1.whenbothprimarypowerandauxiliarypowerattheinputoftheexpresscardpowerswitchareoff,thenall
powertotheexpresscardconnectorisoffregardlessofwhetheracardispresent.
2.whenbothprimarypowerandauxiliarypowerattheinputoftheexpresscardpowerswitchareon,然后
powerisonlyappliedtotheexpresscardaftertheexpresscardpowerswitchdetectsthatacardispresent.
3.whenprimarypower(either+3.3vor+1.5v)attheinputoftheexpresscardpowerswitchisoffand
auxiliarypowerattheinputoftheexpresscardpowerswitchison,thentheexpresscardpowerswitch
behavesinthefollowingmanner:
一个.ifneitherofthecardpresentinputsisdetected(nocardinserted),thennopowerisappliedtothe
expresscardslot.
b.ifthecardisinsertedafterthesystemhasenteredthispowerstate,thennopowerisappliedtothe
expresscardslot.
c.ifthecardisinsertedpriortotheremovaloftheprimarypower(either+3.3vor+1.5vorboth)atthe
inputoftheexpresscardpowerswitch,thenonlytheprimarypower(both+3.3vand+1.5v)isremoved
andtheauxiliarypowerissenttotheexpresscardslot.
figure18throughfigure23illustratethetimingrelationshipsbetweenpower/logicinputsandoutputsof
expresscard.
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