www.德州仪器.com
使能
UNDERVOLTAGELOCKOUT
同步
POWERGOODCOMPARATOR
低-batterydetector
TPS62110
TPS62111
TPS62112
SLVS585–JULY2005
detaileddescription(持续)
logiclowonenforcesthetps6211xintoshutdown.inshutdown,thepowerswitch,驱动器,voltagereference,
振荡器,andallotherfunctionsareturnedoff.thesupplycurrentisreducedtolessthan2µaintheshutdown
模式.whenthedeviceisinthermalshutdown,thebandgapisforcedtobeswitchedonevenifthedeviceisset
intoshutdownbypullingentognd.
ifanoutputvoltageispresentwhenthedeviceisdisabled,whichcouldbeduetoanexternalvoltagesourceora
supercapacitor,thereverseleakagecurrentisspecifiedunderelectricalcharacteristics.pullingtheenablepin
highstartsupthetps6211xwiththesoftstart.iftheenpinisconnectedtoanyvoltageotherthanv
I
orgnd,
anincreasedleakagecurrentoftypically10µaandupto20µacanoccur.
theundervoltagelockoutcircuitpreventsthedevicefrommisoperationatlow-inputvoltages.itpreventsthe
converterfromturningontheswitchorrectifiermosfetunderundefinedconditions.theminimuminputvoltage
tostartupthetps6211xis3.4v(worstcase).thedeviceshutsdownat2.8vminimum.
ifnoclocksignalisapplied,theconverteroperateswithatypicalswitchingfrequencyof1mhz.itispossibleto
synchronizetheconvertertoanexternalclockwithinafrequencyrangefrom0.8mhzto1.4mhz.thedevice
automaticallydetectstherisingedgeofthefirstclockandsynchronizesimmediatelytotheexternalclock.ifthe
clocksignalisstopped,theconverterautomaticallyswitchesbacktotheinternalclockandcontinuesoperation.
theswitchoverisinitiatedifnorisingedgeonthesyncpinisdetectedforadurationoffourclockcycles.
因此,themaximumdelaytimecanbe6.25µsiftheinternalclockhasitsminimumfrequencyof800khz
ifthedeviceissynchronizedtoanexternalclock,thepowersavemodeisdisabled,andthedevicesstayin
forcedpwmmode.
connectingthesyncpintothegndpinenablesthepowersavemode.theconverteroperatesinthepwm
modeatmoderate-至-heavyloads,andinthepfmmodeduringlightloadswhichmaintainshighefficiencyovera
wideloadcurrentrange.
thepowergood(pg)comparatorhasanopen-drainoutputcapableofsinking1ma(典型).thepgisonly
activewhenthedeviceisenabled(en=高).whenthedeviceisdisabled(en=低),thepgpinispulledto
地.
thepgoutputisonlyvalidaftera250-µsdelaywhenthedeviceisenabled,andthesupplyvoltageisgreater
thantheundervoltagelockoutV
(uvlo)
.pgislowduringthefirst250µsaftershutdownandinshutdown.
thepgpinbecomesactivehighwhentheoutputvoltageexceeds98.4%(典型)ofitsnominalvalue.leave
thepgpinunconnectedwhennotused.
thelow-batteryoutput(lbo)isanopen-draintypewhichgoeslowwhenthevoltageatthelow-batteryinput
(lbi)fallsbelowthetrippointof1.256v
±
1.5%.thevoltageatwhichthelow-batterywarningisissuedcanbe
adjustedwitharesistivedividerasshowninFigure19.thesumofresistors(r1+r2)aswellasthesumof(r5
+r6)isrecommendedtobeinthe100-k
Ω
to1-m
Ω
rangeforhighefficiencyatlowoutputcurrent.anexternal
pullupresistorcanbeconnectedtoout,oranyothervoltagerailinthevoltagerangeof0vto16v.在
开始-向上,thelbooutputsignalisinvalidforthefirst500µs.lboishighimpedancewhenthedeviceisdisabled.
ifthelow-batterycomparatorfunctionisnotused,connectlbitoground.thelow-batterydetectorisdisabled
whenthedeviceisdisabled.
thelogiclevelofthelbopinisnotdefinedforthefirst500µsafterenispulledhigh.
whenthelbiisusedtosupervisethebatteryvoltageandshutdownthetps62111atlow-inputvoltages,这
batteryvoltageriseswhenthecurrentdropstozero.theimplementedhysteresisonthelbipinmaynotbe
sufficientforalltypesofbatteries.Figure19showshowanadditionalexternalhysteresiscanbeimplemented.
14
: 点此下载
