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POWER MANAGEMENT Description
TheSC635isahigh-currentchargepumpdesignedspecificallyforusewithwhiteLEDsusedincameraflashapplications.Onlytwosmallbucketcapacitorsarerequired todeveloptheoutputdrive,providingalowEMIsolution comparedtoinductiveboostregulators.
Charge Pump Flash LED Driver
Features
SC635
Twoselectablemodes-FlashandSpotlight 200mAmaxoutput-FlashMode Spotlightmodesetto40%ofFlashCurrent 3.0Vto5.25VInputRange Externalpinsforcontrolofflashandspotlightmodes forsynchronizationtoacameramoduleorgraphics TheSC635hastwomodesofoperation:Flashmodeand controller Spotlightmode.InFlashmode,theSC635iscapableof u Shortcircuit,over-voltage,andover-temperature delivering 200mA to a high-intensity LED during image protection capture.InSpotlightmodetheSC635outputs40%ofthe u Soft-startfunctionality Flashmodecurrentforgeneralpurposelightingorstatus u MicroLeadPackageMLPD-0,3mmx3mm indication. u u u u u AnexternalresistorisconnectedinserieswiththeLEDto setthecurrent.InFlashmode,thisresistorcandissipate upto50mW,reducingthepowerdissipationrequirement oftheSC635.Theflashinput(FLASH)overridesthecontrolinput(CTRL)tomakesuretheflashfunctionisactivatedwhencalledfor. ThethermallyefficientMLPD-10packageandceramicbypassandbucketcapacitorsmaketheSC635ahighoutputcurrentdriverthatrequiresminimalPCBarea.
Applications
u MobileCameraPhones u DigitalCameras u PDAswithBuilt-inCameras
TypicalApplicationCircuit TypicalApplicationCircuit
1
VIN C1+ C1C2+ C2-
SC635
VOUT GND ISET CTRL
9 3 6 7 5
VBAT
10F 1F
8 4 10
1F
white LED
1F
2
FLASH
RSET
FLASH CTRL
December2,2005
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SC635
POWER MANAGEMENT AbsoluteMaximumRatings
Exceedingthespecificationsbelowmayresultinpermanentdamagetothedeviceordevicemalfunction.Operationoutsideoftheparametersspecifiedinthe ElectricalCharacteristicssectionisnotimplied.
Parameter Input Supply Voltage Output Voltage Pin Voltage - FLASH, CTRL, ISET, C1-, C2Pin Voltage - C1+, C2+ Thermal Resistance, Junction to Ambient (JESD51 Standard Method)(1) VOUT Short Circuit Duration Operating Ambient Temperature Range Junction Temperature Range Storage Temperature Range Peak IR Flow Temperature ESD Protection Level(2)
Symbol VVIN VVOUT
Maximum -0.3 to +6.5 -0.3 to +6.5 -0.3 to VVIN + 0.3 -0.3 to VVOUT + 0.3
Units V V V V C/W s C C C C kV
qJA
SC TA TJ TSTG TLEAD VESD
49 Indefinite -40 to +85 -40 to +150 -60 to +150 260 2
(1)Calculatedfrompackageinstillair,mountedto3"x4.5",4layerFR4PCBwiththermalviasundertheexposedpadasperJESD51standards. (2)TestedaccordingtoJEDECstandardJESD22-A114-B.
ElectricalCharacteristics
Unlessotherwisespecified:TA=25CforTYP,-40Cto+60CforMINandMAX; CBUCKET=COUT=1.0F(ESR<0.1);CIN=10.0F;VVIN=3.0Vto5.25V;VVOUT=2.8Vto4.25V;RSET=0.5(0.1%).
Parameter
Symbol
Conditions FLASH high, RISET = 1.25W 3.3V < VVIN < 4.2V 2.8V < VVOUT = 4.25V FLASH low, CTRL high, RISET = 1.25W 3.0V < VVIN < 4.5V 2.8V < VVOUT < 4.5V FLASH high, RISET = 1.25W 3.3V < VVIN < 4.2V 2.8V < VVOUT < 4.25V FLASH low, CTRL high, RISET = 1.25W 3.0V < VVIN < 4.5V 2.8V < VVOUT < 4.5V FLASH high
Min 184
Typ 200
Max 216
Units
Output Current
IOUT
mA 68 80 92
230
250
270 mV
ISET Reference Voltage
VISET
85
100 3.4 2.0 0.1
115 5.0 4.5 2.0 mA mA A
Quiescent Current
IQ
FLASH low, CTRL high FLASH low, CTRL low
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SC635
POWER MANAGEMENT ElectricalCharacteristics(Cont.)
Parameter Flash Mode Start-up Time(1) Flash Mode Pulse Duration Spotlight Mode Start-up Time(1) Oscillator Frequency Oscillator Frequency Accuracy Short-circuit Output Current Limit Input Current Limit Over-temperature Protection(1) Logic Input High Threshold Logic Input Low Threshold Logic Input High Current Logic Input High Current ISET Ripple Voltage(1) Symbol tF-SU tFLASH tS-SU fOSC DfOSC ISC ILIMIT TOT VIH VIL IIH IIL VISET(P-P) VOUT shorted to GND 3.3V < VVIN < 4.2V 1.0 150 Hysteresis FLASH, CTRL FLASH, CTRL FLASH CTRL FLASH, CTRL Spotlight mode - IOUT = 80mA FLASH mode - IOUT = 200mA 1 2 20 40 0.1 25 100 10 1.5 0.4 35 70 2.0 Conditions t = 0 when FLASH goes high to IOUT = 90% of final value 3.3V < VVIN < 4.2V IOUT = 200mA, VVOUT > 2.8V t = 0 when CTRL goes high to IOUT = 90% of final value Device enabled -15 250 15 465 2.1 indefinite 1 Min Typ Max 1 Units ms s ms kHz % mA A C V V A A mV
Notes: (1)Guaranteedbydesign-nottestedinproduction.
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SC635
POWER MANAGEMENT
PinConfiguration
OrderingInformation
DEVICE SC635MLTRT((1)(2)
2)(1)
PACKAGE(
1)
MLPD-10 3x3 Evaluation Board
VIN C2GND C1FLASH
1 2 3 4 5 T
10
C2+ VOUT C1+ CTRL ISET
TOPVIEW
9 8 7 6
SC635EVB
Notes: (1) Available in tape and reel only. A reel contains 3,000 devices. (2) Available in lead-free package only. Device is WEEE and RoHS compliant.
MLP10:3X310LEAD
PinDescriptions
Pin# 1 2 3 4 5 6 7 8 9 10 T Pin Name VIN C2GND C1FLASH ISET CTRL C1+ VOUT C2+ Thermal Pad Pin Function Input voltage. Negative terminal of bucket capacitor 2. Ground - connect to ground plane using multiple vias. Negative terminal of bucket capacitor 1. Flash mode enable pin - puts the device in active Flash mode when high and also overrides CTRL. Current-setting reference pin - connect to the LED cathode and the current setting resistor. Control input bit - used to enable and set the output current in Spotlight mode when high. Positive terminal of bucket capacitor 1. Output pin. Positive terminal of bucket capacitor 2. Pad for heat sinking purposes - not connected internally. Connect to ground plane using multiple vias.
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SC635
POWER MANAGEMENT PinConfiguration ApplicationsInformation
ProtectionCircuitry TheSC635alsoprovidesprotectioncircuitrythatprevents thedevicefromoperatinginanunspecifiedstate.These functions include Input Over-Voltage Protection (IOVP), In Flash mode the SC635 output can drive 200mA at Output Over-Voltage Protection (OVP), Over-Temperature 4.25V into an LED for an unlimited duration under all (OT)Protection,Over-CurrentProtection(OCP),andShorttemperatureandinputconditions.TheFLASHpinisused CircuitCurrentProtection(SCCP). to trigger this mode(activehigh). In Spotlight modethe SC635regulatestheoutputcurrentto40%oftheFlash Input Over-Voltage Protection mode current setting when the CTRL pin is pulled high Inputover-voltageprotectionisincludedtopreventoperaandtheFLASHpinislow.NotethatFlashmodehasprior- tionathighinputvoltagesthatcoulddamagethedevice. ityoverSpotlightmode,i.e.,theFLASHpintriggersFlash TheIOVPcircuitsensestheinputvoltageanddetermines whenthesupplyexceeds6V.Hysteresisisincludedinthis moderegardlessofthestateoftheCTRLpin. circuittoavoidchatteringbetweenstates.WhenthevoltOutput current is regulated by attaching the ISET pin to agerisesabovethisthreshold,thedeviceisdisabledunthecathode(s)oftheLEDpackageandalowresistance tiltheinputvoltagedropstoalevelwithinthespecified sense resistor (typically 1.25). The ISET pin monitors range. thevoltageatthecathodeandsignalsthechargepump toincreaseordecreasetheoutputcurrentuntiltheISET Output Over-Voltage Protection voltage reaches the programmed setting. The resistor Outputover-voltageprotectionisincludedtopreventthe valueischosentosetthecurrentthroughtheLEDbased SC635fromgeneratinganoutputvoltagethatcoulddamageotherdevicesconnectedtoitsuchasloadLEDsand onthisreferencevoltage. bypasscapacitors.Whentheoutputvoltageexceeds5.5V, theOVPcircuitdisablesthechargepumpuntilthevoltage FlashMode FlashmodeisenabledwhenevertheFLASHpinispulled decreases to a level within the acceptable range. This highandremainsactiveuntiltheFLASHpinisreleased. circuitallowsthedevicetodriveLEDswithhighforward ThismodehashigherprioritythanSpotlightmode,sothe voltagesatareducedlevelwithoutexceedingtheoutput stateoftheCTRLpinisoverriddenwhenevertheFLASH voltagelimitsspecifiedforthedevice.Note,however,that pinisactivated.WhileinFlashmodethereferencevolt- thiseffectisaconsequenceoftheOVPcircuitandisnot itsintendedpurpose. ageontheISETpinissetto250mV. Outputcurrentsotherthantheratedmaximumof200mA Over-Temperature Protection can be set by changing the RISET value. In Flash mode, The over-temperature circuit helps prevent the device from overheating and experiencing a catastrophic failIOUT=250mV/RISET. ure.Whenthejunctiontemperatureexceeds150Cthe deviceisdisabled.Itremainsdisableduntilthejunction SpotlightMode Spotlight mode is enabled by setting the CTRL pin high temperaturedropsbelowthisthreshold.AswiththeUVLO andkeepingtheFLASHpinlow.WheninSpotlightmode, andOVPcircuits,hysteresisisincludedtopreventtoggling theSC635canmaintainaconstantcurrentindefinitelyto betweenmodes. driveanLEDorbankofLEDs.TheISETreferencevoltage issetto00mVsothattheoutputcurrentismaintained Over-Current Protection at80mAwhena1.25resistorisused.Spotlightcurrent When the SC635 is in 2X mode, the input current will isalways40%offlashcurrentforanygivenvalueofRISET. beapproximatelydoubletherequiredoutput.Whenthe Inspotlightmode,IOUT=100mV/RISET.Theresistorval- steady-stateloadrequiresthemaximumcurrentavailable ueshouldnotexceed2,however,toensuretheSC635 in2Xmode,theOCPcircuitpreventsthedevicefromoverdoesnotbecomeunstablewhileinSpotlightmodedueto heatingduetoexcessivepowerdissipation.
2005SemtechCorp. www.semtech.com
GeneralOperation The SC635 is a powerful 2X charge pump designed to drive a high-intensity white LED with a constant current (Spotlightmode)orwithapulsedcurrentofhigherintensity(Flashmode)usedforcameraflash.
theoutputcurrentbeingsettoolow.
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SC635
POWER MANAGEMENT
ApplicationsInformation(Cont.)
Short-Circuit Current Protection Short-circuitcurrentprotectionisprovidedtolimitthecurrent that can be sourced when the output is shorted to ground.WhenashortcircuitforcesVOUTtodropbelow 2V,theSCCPdetectstheconditionandlimitstheoutput current. ResistorSelection TheISETresistorselectioniscriticalingeneratingthecorrectcurrent.ThevaluecanbechosentosettheSpotlight modecurrentortheFlashmodecurrent,butitmustbe notedthatthetwocurrentsettingsaredependentonthe sameresistance.Itisrecommendedthattheresistorbe selectedtomatchthedesiredLEDcurrentforFlashmode. ThisallowsthedesignertosettheSC635'smaximumcurrent and select the resistor package size necessary for thepowerdissipationrequiredinFlashmode.Thetypical applicationshownonpage1usesa1.25resistortoset aflashmodecurrentof200mAandspotlightmodecurrentof80mA.Ahighprecisionresistorshouldbeusedto ensurethespecifiedaccuracyforLEDcurrent. To avoid malfunction of the charge pump, it is recommendedthattheresistanceseenattheISETpinremain constant while the device is active (Flash or Spotlight mode). Changing the resistance value or the load currentwhilethedeviceisactivecouldcauseinstabilitythat wouldresultinnon-compliantbehavior. TheloadcurrentreturnpathisfromtheISETsensepoint throughtheresistorandbacktothegroundpins.Resistanceinthispathaddstothetotalresistanceandhasthe effectofreducingtheLEDcurrentbyabout4%per0mV ofDCdropacrossthereturncoppertraceinflashmode. Forthisreason,itiscrucialtohavealowresistancereturn path.Placeandgroundtheresistorascloseaspossible tothegroundpinoftheSC635.ThetracefromtheISET pinhasvirtuallynocurrent.TheISETtraceshouldmake contactatthepadofthepowersenseresistortominimize theeffectofvoltagedropbetweentheLEDcathodeand theresistor. CapacitorSelection The SC635 is designed to use low-ESR ceramic capacitorsfortheinputandoutputbypasscapacitorsaswellas thechargepumpbucketcapacitors.Idealperformance isachievedwhenCisexactlyequaltoC2.ItisrecommendedthatX5RorX7Rceramiccapacitorsbeusedfor bestperformance. ThermalResistance TheSC635packageisthermallyefficientwhenthecircuit board layout connects the thermal pad though multiple viastothegroundplane.Thethermalresistanceisrated at49C/W,andthisratingisdependentontheconnection betweenthethermalpadandthegroundplane. A layoutthatisdonecorrectlyshouldkeepthejunctiontemperature below the OT limit while operating the SC635 withinthespecifiedelectricalconditionsforIOUTandVISET. Apoorlayoutmayallowthejunctiontemperaturetoreach theOTlimitwhileinFlashorSpotlightmode.Itiscritical tomaintainadequategroundplanearoundthedeviceto maximizeheattransferandavoidover-temperatureshutdown.
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SC635
POWER MANAGEMENT TypicalCharacteristics
200mAFlashDuration,RISET=1.25W, VOUT=3.30V(start)to3.25V(LEDheated500ms)
205.0
FlashCurrentat500ms,RISET=1.25W,VOUT=3.25V
205.0
203.0
203.0
LED Current [mA]
201.0
VIN = 4.2V VIN = 3.7V VIN = 3.3V
199.0
197.0
195.0 0 100
LED Current [mA]
201.0
199.0
197.0
195.0
Pulse Duration [ms]
200
300
400
500
3.3
3.45
3.6
VIN [V]
3.75
3.9
4.05
4.2
FlashCurrentat100ms,RISET=1.25W,VOUT=3.28V
205.0
FlashCurrentat10ms,RISET=1.25W,VOUT=3.30V
205.0
203.0
203.0
LED Current [mA]
201.0
199.0
197.0
195.0 3.3 3.45 3.6
VIN [V]
3.75
3.9
4.05
4.2
LED Current [mA]
201.0
199.0
197.0
195.0 3.3 3.45 3.6
VIN [V]
3.75
3.9
4.05
4.2
80mASpotlightCurrent,RISET=1.25W,VOUT=2.96V
85.0
83.0
LED Current [mA]
81.0
79.0
77.0
75.0 3 3.45 3.9
VIN [V]
4.35
4.8
5.25
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SC635
POWER MANAGEMENT
TypicalCharacteristics(Cont.)
FlashModeRipple,RISET=1.25W SpotlightModeRipple,RISET=1.25W
Ch150mV/div Ch2200mV/div Ch3200mV/div 4us/div
Ch150mV/div Ch2100mV/div Ch3100mV/div 4us/div
StartupFlashMode200mA
Ch1100mV/div Ch22V/div Ch32V/div Ch42V/div 40us/div
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SC635
POWER MANAGEMENT SuggestedLayout
LayoutGuidelines The following layout is suggested for a two-layer design. ThecapacitorsCandC2arethebucketcapacitorsand eachconductsthefullloadcurrentofupto200mApulsed foronehalfclockcycle.C3istheoutputdecouplingcapacitor placed near the SC635 VOUT pin. C4 is the inputdecouplingcapacitorplacedneartheSC635VINpin. Multipleviasshouldbeusedwheneveritisnecessaryto changelayersonnetsconnectingtopinsVIN,VOUT,GND, C1-,C1+,C2-andC2+.ResistorR1isroutedwithavery low resistance connection between R1 and GND pin 3. ThesensetracebetweenPin6andRisroutedaround thegroundvias,allowingtheshortestgroundreturnpath possible.ThesensetraceisconnectedtoRatthepositiveterminalpadforthemostaccurateoutputpossible. Thebottomcopperlayerismostlyagroundplanewithno obstructionsbetweenthegroundvias.ThesmallerrectangletotheleftconnectstheinputpowertoVINpin1and inputcapacitorC4.Thetwotracesatthelowerleftarefor logicinputsFLASHandCTRL.Thetracetotherightisthe ISETpin"sense"trace.Thesensetraceisroutedoutof thepathofthereturninggroundcurrent.
BottomCopper
TopCopper
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SC635
POWER MANAGEMENT
BlockDiagram
VIN
1
LDO
8
C+
250kHz
4
C-
10 C2+ CTRL FLASH 7 5 Reference Voltage Generator LogicControl
CHARGE PUMP
2
C2-
9
VOUT
3
GND
6
ISET
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SC635
POWER MANAGEMENT OutlineDrawing-MLPD-0
A
E
B
DIMENSIONS INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX
A A1 A2 b C D E e L N aaa bbb .031 .039 .000 .002 (.008) .007 .009 .011 .074 .079 .083 .042 .048 .052 .114 .118 .122 .020 BSC .012 .016 .020 10 .003 .004 0.80 1.00 0.00 0.05 (0.20) 0.18 0.23 0.30 1.87 2.02 2.12 1.06 1.21 1.31 2.90 3.00 3.10 0.50 BSC 0.30 0.40 0.50 10 0.08 0.10
E PIN 1 INDICATOR (LASER MARK)
A aaa C C 1 LxN 2 A1 C
SEATING PLANE
A2
D
N e bxN bbb CAB
NOTES:
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS TERMINALS.
MarkingInformation
Top Mark
635 yyww xxxx
yyww = Datecode (Example = 0552) xxxx = Semtech Lot Number
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SC635
POWER MANAGEMENT
LandPattern-MLPD-0
K
DIM
G Y Z C G H K P X Y Z
DIMENSIONS INCHES MILLIMETERS
(.112) .075 .055 .087 .020 .012 .037 .150 (2.85) 1.90 1.40 2.20 0.50 0.30 0.95 3.80
(C)
H
X P
NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET.
ContactInformation
SemtechCorporation PowerManagementProductsDivision 200FlynnRoad,Camarillo,CA302 Phone:(805)498-2111FAX:(805)498-3804
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