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參數(shù)資料
| 型號(hào)： | SC635 |
| 廠商： | Semtech Corporation |
| 英文描述： | Charge Pump Flash LED Driver |
| 中文描述： | 電荷泵閃光LED驅(qū)動(dòng)器 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 357K |
| 代理商： | SC635 |
6
2005SemtechCorp.
www.semtech.com
POWER MANAGEMENT
ApplicationsInformation(Cont.)
SC635
Short-Circuit Current Protection
Short-circuitcurrentprotectionisprovidedtolimitthecur-
rentthatcanbesourcedwhentheoutputisshortedto
ground.WhenashortcircuitforcesVOUTtodropbelow
2V,theSCCPdetectstheconditionandlimitstheoutput
current.
ResistorSelection
TheISETresistorselectioniscriticalingeneratingthecor-
rectcurrent.ThevaluecanbechosentosettheSpotlight
modecurrentortheFlashmodecurrent,butitmustbe
notedthatthetwocurrentsettingsaredependentonthe
sameresistance.Itisrecommendedthattheresistorbe
selectedtomatchthedesiredLEDcurrentforFlashmode.
ThisallowsthedesignertosettheSC635’smaximumcur-
rentandselecttheresistorpackagesizenecessaryfor
thepowerdissipationrequiredinFlashmode.Thetypical
applicationshownonpage1usesa1.25Ωresistortoset
aflashmodecurrentof200mAandspotlightmodecur
-
rentof80mA.Ahighprecisionresistorshouldbeusedto
ensurethespecifiedaccuracyforLEDcurrent.
Toavoidmalfunctionofthechargepump,itisrecom-
mendedthattheresistanceseenattheISETpinremain
constant while the device is active (Flash or Spotlight
mode).Changingtheresistancevalueortheloadcur
-
rentwhilethedeviceisactivecouldcauseinstabilitythat
wouldresultinnon-compliantbehavior.
TheloadcurrentreturnpathisfromtheISETsensepoint
throughtheresistorandbacktothegroundpins.Resis-
tanceinthispathaddstothetotalresistanceandhasthe
effectofreducingtheLEDcurrentbyabout4%per0mV
ofDCdropacrossthereturncoppertraceinflashmode.
Forthisreason,itiscrucialtohavealowresistancereturn
path.Placeandgroundtheresistorascloseaspossible
tothegroundpinoftheSC635.ThetracefromtheISET
pinhasvirtuallynocurrent.TheISETtraceshouldmake
contactatthepadofthepowersenseresistortominimize
theeffectofvoltagedropbetweentheLEDcathodeand
theresistor.
CapacitorSelection
TheSC635isdesignedtouselow-ESRceramiccapaci-
torsfortheinputandoutputbypasscapacitorsaswellas
thechargepumpbucketcapacitors.Idealperformance
isachievedwhenCisexactlyequaltoC2.Itisrecom-
mendedthatX5RorX7Rceramiccapacitorsbeusedfor
bestperformance.
ThermalResistance
TheSC635packageisthermallyefficientwhenthecircuit
boardlayoutconnectsthethermalpadthoughmultiple
viastothegroundplane.Thethermalresistanceisrated
at49°C/W,andthisratingisdependentontheconnec
-
tionbetweenthethermalpadandthegroundplane.A
layoutthatisdonecorrectlyshouldkeepthejunctiontem-
peraturebelowtheOTlimitwhileoperatingtheSC635
withinthespecifiedelectricalconditionsforIOUTandV
.
Apoorlayoutmayallowthejunctiontemperaturetoreach
theOTlimitwhileinFlashorSpotlightmode.Itiscritical
tomaintainadequategroundplanearoundthedeviceto
maximizeheattransferandavoidover-temperatureshut-
down.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC63504L124 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| SC635EVB | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Charge Pump Flash LED Driver |
| SC635MLTRT | 制造商:Semtech Corporation 功能描述:LED DRVR 1Segment 3.3V/5V 10-Pin MLPD T/R |
| SC63610FN116HR2 | 制造商:ON Semiconductor 功能描述: |
| SC63610FN125HR | 制造商:ON Semiconductor 功能描述: |
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