- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄299883 > SC635MLTRT (Semtech Corporation) Charge Pump Flash LED Driver PDF資料下載
參數(shù)資料
| 型號(hào)： | SC635MLTRT |
| 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)： | 8/12頁 |
| 文件大?。?/td> | 357K |
| 代理商： | SC635MLTRT |
5
2005SemtechCorp.
www.semtech.com
POWER MANAGEMENT
SC635
PinConfiguration
ApplicationsInformation
GeneralOperation
The SC635 is a powerful 2X charge pump designed to
driveahigh-intensitywhiteLEDwithaconstantcurrent
(Spotlightmode)orwithapulsedcurrentofhigherinten-
sity(Flashmode)usedforcameraflash.
In Flash mode the SC635 output can drive 200mA at
4.25V into an LED for an unlimited duration under all
temperatureandinputconditions.TheFLASHpinisused
totriggerthismode(activehigh).InSpotlightmodethe
SC635regulatestheoutputcurrentto40%oftheFlash
mode current setting when the CTRL pin is pulled high
andtheFLASHpinislow.NotethatFlashmodehasprior-
ityoverSpotlightmode,i.e.,theFLASHpintriggersFlash
moderegardlessofthestateoftheCTRLpin.
OutputcurrentisregulatedbyattachingtheISETpinto
thecathode(s)oftheLEDpackageandalowresistance
sense resistor (typically 1.25Ω). The ISET pin monitors
thevoltageatthecathodeandsignalsthechargepump
toincreaseordecreasetheoutputcurrentuntiltheISET
voltage reaches the programmed setting. The resistor
valueischosentosetthecurrentthroughtheLEDbased
onthisreferencevoltage.
FlashMode
FlashmodeisenabledwhenevertheFLASHpinispulled
highandremainsactiveuntiltheFLASHpinisreleased.
ThismodehashigherprioritythanSpotlightmode,sothe
stateoftheCTRLpinisoverriddenwhenevertheFLASH
pinisactivated.WhileinFlashmodethereferencevolt-
ageontheISETpinissetto250mV.
Outputcurrentsotherthantheratedmaximumof200mA
canbesetbychangingtheR
ISET value. In Flash mode,
IOUT=250mV/R
ISET.
SpotlightMode
SpotlightmodeisenabledbysettingtheCTRLpinhigh
andkeepingtheFLASHpinlow.WheninSpotlightmode,
theSC635canmaintainaconstantcurrentindefinitelyto
driveanLEDorbankofLEDs.TheISETreferencevoltage
issetto00mVsothattheoutputcurrentismaintained
at80mAwhena1.25Ωresistorisused.Spotlightcurrent
isalways40%offlashcurrentforanygivenvalueofR
ISET.
Inspotlightmode,IOUT=100mV/R
ISET.Theresistorval-
ueshouldnotexceed2,however,toensuretheSC635
doesnotbecomeunstablewhileinSpotlightmodedueto
theoutputcurrentbeingsettoolow.
ProtectionCircuitry
TheSC635alsoprovidesprotectioncircuitrythatprevents
thedevicefromoperatinginanunspecifiedstate.These
functions include Input Over-Voltage Protection (IOVP),
Output Over-Voltage Protection (OVP), Over-Temperature
(OT)Protection,Over-CurrentProtection(OCP),andShort-
CircuitCurrentProtection(SCCP).
Input Over-Voltage Protection
Inputover-voltageprotectionisincludedtopreventopera-
tionathighinputvoltagesthatcoulddamagethedevice.
TheIOVPcircuitsensestheinputvoltageanddetermines
whenthesupplyexceeds6V.Hysteresisisincludedinthis
circuittoavoidchatteringbetweenstates.Whenthevolt-
agerisesabovethisthreshold,thedeviceisdisabledun-
tiltheinputvoltagedropstoalevelwithinthespecified
range.
Output Over-Voltage Protection
Outputover-voltageprotectionisincludedtopreventthe
SC635fromgeneratinganoutputvoltagethatcoulddam-
ageotherdevicesconnectedtoitsuchasloadLEDsand
bypasscapacitors.Whentheoutputvoltageexceeds5.5V,
theOVPcircuitdisablesthechargepumpuntilthevoltage
decreases to a level within the acceptable range. This
circuitallowsthedevicetodriveLEDswithhighforward
voltagesatareducedlevelwithoutexceedingtheoutput
voltagelimitsspecifiedforthedevice.Note,however,that
thiseffectisaconsequenceoftheOVPcircuitandisnot
itsintendedpurpose.
Over-Temperature Protection
The over-temperature circuit helps prevent the device
from overheating and experiencing a catastrophic fail-
ure.Whenthejunctiontemperatureexceeds150°Cthe
deviceisdisabled.Itremainsdisableduntilthejunction
temperaturedropsbelowthisthreshold.AswiththeUVLO
andOVPcircuits,hysteresisisincludedtopreventtoggling
betweenmodes.
Over-Current Protection
When the SC635 is in 2X mode, the input current will
beapproximatelydoubletherequiredoutput.Whenthe
steady-stateloadrequiresthemaximumcurrentavailable
in2Xmode,theOCPcircuitpreventsthedevicefromover-
heatingduetoexcessivepowerdissipation.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SC804AMLTRT | Fully Integrated 4.4V Lithium-Ion Battery Charger System with Timer |
| SC804A | Fully Integrated 4.4V Lithium-Ion Battery Charger System with Timer |
| SC804EVB | Fully Integrated Lithium-Ion Battery Charger System with Timer |
| SC804IMLTRT | Fully Integrated Lithium-Ion Battery Charger System with Timer |
| SC804 | Fully Integrated Lithium-Ion Battery Charger System with Timer |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC63610FN116HR2 | 制造商:ON Semiconductor 功能描述: |
| SC63610FN125HR | 制造商:ON Semiconductor 功能描述: |
| SC63610FN125HR2 | 制造商:ON Semiconductor 功能描述: |
| SC63610FN131HR2 | 制造商:ON Semiconductor 功能描述: |
| SC63610L115H | 制造商:ON Semiconductor 功能描述: |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。