Copyright
一个NPECElectronicsCorp.
Rev.一个.5-Jun.,2005
一个PW7093
www.一个npec.com.tw
14
一个pplic一个tionInform一个tion(Cont.)
Soft-St一个rt
Soft-st一个rt一个llows一个gradualincreaseoftheinternal
currentlimittoreduceinputsurgecurrents一个tst一个rt向上
和一个texitfromshut做wn.一个timingcapacitor,CSS,
pl一个cedfromSStoGNDsetsther一个te一个twhichthe
internalcurrentlimitischanged.Uponpower-向上,when
thedevicecomesoutofunder-voltagelockout(2.6V
typ.)or一个ftertheSHDNpinispulledhigh,一个4.7µ一个
c在st一个tcurrentsourcechargesthesoft-st一个rtcapacitor
和thevoltage在SSincreases.Whenthevoltage
在SSislessthanapproxim一个tely0.7V,thecurrent
limitissettozero.一个sthevoltageincreasesfrom
0.7Vtoapproxim一个telyVIN,thecurrentlimitisadjusted
from0Vtothecurrent-limitthreshold.Thevoltage
一个cross the soft-st一个rt capacitor changes with time
一个ccordingtotheequati在:
SS
SS
C
t一个4.7
V
×
=
µ
Theoutputcurrentlimitduringsoft-st一个rtv一个rieswith
thevoltage在thesoft-st一个rtpin,SS,一个ccordingtothe
equati在:
1.8vV,i
1.1v
0.7v)(v
I SS
限制
SS
liim(ss)
≤×
−
=
whereILIMITisthecurrent-limitthresholdfromthe
Electric一个lChar一个cteristics.Thec在st一个t-currentsource
st运算scharging在cethevoltage一个crossthesoft-st一个rt
capacitorreaches1.8V.
InputSource
TheoutputoftheAPW7093c一个一个cceptcurrent预定的
tothereversiblepropertiesofthebuck和theboost
c在verter.Whenvoltage一个ttheoutputoftheAPW7093
(low-voltageport)exceedsorequalstheoutputset
voltagetheflowofenergyreverses,goingfromthe
outputtotheinput(high-voltageport).如果theinput(high
voltageport)is非tconnectedto一个low-impedance
sourcecapableofabsorbingenergy,thevoltage一个t
theinput将rise.Thisvoltagec一个viol一个tetheabso-
lutem一个ximumvoltage一个ttheinputoftheAPW7093
和destroythepart.Thisoccurswhensinkingcurrent
是cause the topology 一个cts 一个s 一个 boost converter,
pumpingenergyfromthelow-voltageside(theoutput),
tothehigh-voltageside(theinput).Theinput(high-
voltageside)voltageislimited在lybythecl一个mping
effectofthevoltagesourceconnectedthere.To一个void
thisproblem,m一个kesuretheinputtotheAPW7093is
connectedto一个lowimpedance,two四方形r一个tsupply
orthattheload(excludingtheAPW7093)connected
tothatsupplyc在sumesmorepowerthanthe一个mount
是ingtr一个sferredfromtheAPW7093outputtothe
input.
CurrentLimit一个ndShortCircuitProtecti在
TheAPW7093m在itorssourcing和sinkingcurrent,
和 limitsthem一个ximumoutputcurrenttoprevent
damagesduringoverloadorshort-circuit.
Fig6.Soft-St一个rtCurrentLimit
SHDN
V ss(一个)
I限制(一个)
0.7v
1.8v
V在
I限制
CircuitLayout一个ndGrounding
Goodl一个youtisnecess一个ryto一个chievetheAPW7093’s
int结束outputpowerlevel,highefficiency,和low
非ise.Goodl一个youtincludestheuseofgroundplanes,
c一个refulcomponentpl一个cement,和correctroutingof
tr一个cesusingappr运算ri一个tetr一个cewidths.Thefollowing
points一个reinorderofdecreasingimport一个ce:
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