Issi Is31lt3135-v1 User manual

IS31LT3135V1,IS31LT3135V2

DualCh.(Main/Sub)LEDDriverEvaluationBoardGuide

Integrated Silicon Solution, Inc. – http://www.issi.com 1

V2, 4/23/2012

Description

TheIS31LT3135isadual‐channelLEDdriverthathastwo

modesofoperation;itcanfunctionasthemain‐channel

driverorasasub‐channelsource.Whenoperatinginmain

mode,thedevicefunctionsasaconstantcurrentsource

thatoutputsanadjustablecurrent,viaanexternalresistor,

throughthemainLED.Thedeviceisoperablewitha

dropoutvoltageof0.1Vwhiledrivinga200mAcurrent.

Whenoperatingasasub‐channeldriver,theICgroundsthe

LED’scathode.Thedevicenormallyoperateswithasingle

channelpoweredon,allowingforquickswitchingbetween

themainandsubchannelmodes.Asweepingpower

supplythatoperatesbetweenhighandlowvoltages,

allowsforsimpleswitchingbetweensub/main‐channel

modes,evenduringconditionswheretheUVpinisbelow

the1.17V(typical)UVthresholdIS31LT3135‐V1;or1.23V

(typical)UVthresholdforIS31LT3135‐V2.Thesweeping

powersupplyallowssub‐channeltomainchannel

switchingduringconditionswheretheUVpinis≥80mV

thantheUVthreshold.Inaddition,themainchannel

featuresshortprotectionviaswitchingtosub‐channelif

anyabnormalbehaviorsoccurinthemain‐channelLED

circuitry.

Features

Powersupplyunder‐voltagedetection

Main‐channelLEDshortprotection

Over‐temperatureprotection

Inputvoltagerange:2.7Vto5.5V

Main/sub‐channeladjustableoutputcurrent

(Setviauser‐configurableexternalresistors)

Main‐channeldropoutVDP=0.1V

Ultra‐lowquiescentcurrent

SOP‐8Package,smallPCBfootprintsize

QuickStart



Figure1:PhotoofIS31LT3135V1/V2evaluationboard



RecommendedEquipment

5VDCPowersupply

1WLED

Multi‐meter

RecommendedI/ORatings

Powersupplyvoltage:3.8VDC

OutputofI

MAIN

:320mAperLED

OutputofI

SUB

:20mAperLED

Note:Whenthepowersupplyvoltage≥LEDvoltagerating,extravoltage

isdissipatedthroughthemain‐channel,causingadropinsystem

efficiencyandanincreaseinwastedenergy.

AbsoluteMaximumRatings

Inputvoltage≤5VDC

Caution:Donotexceedtheinputvoltageconditionslistedaboveto

avoidriskingpermanentdamagetotheboard.

OrderingInformation



PartNumberTemperatureRangeICPackage

IS31LT3135‐V1GRLS2‐EB

IS31LT3135‐V2GRLS2‐EB−40°Cto+85°C(IndustrialGrade)SOP‐8(5mmx4mm)

Table1:OrderingInformationforIS31LT3135‐V1/V2evaluationboard.

Customerswithinquiriesregardingpricing,delivery,partavailability,andrelatedinformation,can

reachISSIAnalogmarketingviaeitherofthefollowingmethods:

Email:[email protected]om

/

Phone:+1(408)969‐6600



IS31LT3135V1,IS31LT3135V2

DualCh.(Main/Sub)LEDDriverEvaluationBoardGuide

Integrated Silicon Solution, Inc. – http://www.issi.com 2

V2, 4/23/2012

Procedure

TheIS31LT3135evaluationboardcomesassembledandequippedwiththepurposeofallowingtheusertoeasily

demonstrate,orevaluate,functionsoftheICdriver.Inordertoverifydeviceoperation,pleasefollowthelisteddirections

carefully.

Caution:Whenpoweringonthecircuit;ensurethatallconnectionsareproperlylinkedtocompletetheboardcircuitry.

1. ConnectthenegativeterminalofthepowersupplytotheGNDpin.

2. ConnectthepositiveterminalofsupplytotheVCCpin.

3. ConnectthenegativeendoftheLEDpanel(LEDarrays)totheLED−terminal.

4. ConnectthepositiveendoftheLEDpanel(LEDarrays)totheLED+terminal.

5. Afterensuringconnectionsaresoundandthatthecircuitiscomplete,turnonthepowersupplytodrivecurrent

throughtheLEDpanel(LEDarrays)andperformevaluation.



Figure2:IS31LT3135evaluationboardcircuitschematic.

BillofMaterials



NameDescriptionSymbolQuantity

Capacitor10uF±20%,16V,Surface‐mount,0805C11

100nF±20%,50V,Surface‐mount,0603C21

Resistor

51K±1%,Surface‐mount,0805(V1)R11

47K±1%,Surface‐mount,0805(V2)

30K±1%,Surface‐mount,0805R21

30K±1%,Surface‐mount,0805R31

33±1%,Surface‐mount,0805R41

DiodeSchottkytype,SS16,1A,60V,SMAD11

HBLEDDriverICIS31LT3135,SOP‐8PackageU11

Table2:IS31LT3135BillofMaterials.RefertoFigure2forspecificcomponentlocations

IS31LT3135V1,IS31LT3135V2

DualCh.(Main/Sub)LEDDriverEvaluationBoardGuide

Integrated Silicon Solution, Inc. – http://www.issi.com 3

V2, 4/23/2012

DeviceOperation

MainChannelLEDOutputCurrent

Themain‐channelLEDcurrentisadjustedbyusingaresistorconnectedtoIsetpin.ThevoltageofIsetpinwillremainat1.2V,

independentofexternalfactorsincludingtransienttemperatureandsourcevoltagefluctuations.Thethroughthe

main‐channelLEDiscalculatedbyusingthefollowingequation:

SET

MAIN R

8000I  

Themain‐channelcurrentwillcontinuethroughtheLEDtotheGNDpin.0.1Vdropoutvoltageoccurswhenthe

main‐channelcurrentis≤200mA.

Sub‐channelLEDcurrentoriginatesfromtheSUBterminaltoground,andlikewiseitscorrespondingLEDcurrentcanbeset

viaanexternalresistor.

SUB4

D2F2CC

SUB RR VVV

I





VCCisthepowersupplyvoltage.VF2isthesub‐LEDvoltage.VD2denotesthediodevoltageanditsvalueshouldbeminimized.

UVThresholdConfiguration

TheUVpindetectsanyvoltageswingsandcompensatesbyutilizing0.8vhysteresis.Thisformoferrorcorrection

mechanismwillensurereliabledeviceoperation,evenwhenthepowersupplyexperiencesanunwantedrippleeffect.

Sweepingpowersupplyfromahightolowvoltage,resultsinmainchannelswitchtosub‐channelwhileUVpinisbelowthe

UVthresholdof1.17V(IS31LT3135‐V1typical)or1.23V(IS31LT3135‐V2typical.)Sweepingpowersupplyfromalowtohigh

voltage,willcausethesub‐channelmodetoswitchbacktomain‐channeloperation,underconditionswhereUVpinis80mV

higherthantheUVthreshold.UuvissetbytheratioofresistorR1overresistorR2.

When1.23V(V2)or(V1)V1.17V

RR RCC

2













;animmediateswitchfrommaintosub‐channeloperation

occurs.Lithium‐ionbatteriestypicallymaintainavoltagelevelof3.7Vduringdischarge,sotherecommendedUVthreshold

is3.4V.TypicallyresistorsR1andR2aresetto10Kmagnitude（i.e.51k）SmallresistancevaluesforR1andR2will

translatetolossesinheatorefficiency.Tominimizetheselosses,itisrecommendedtoderiveprecisevaluesforthe

resistorssothattheenddeviceoperateswiththehighestefficiencyrateachievable.

ShortCircuitProtectionMechanism

Whenthemain‐channelLEDisshorted,IS31LT3135willautomaticallyswitchtosub‐channelmode.

PCBlayoutreference

Theswitchshouldbeplacedinanareawithlowvoltages,toavoidaninstantsparkwhileswitching.Thetracesbetween

GNDpinandISETpintorealgroundshouldbeasshortandwideaspossible,withthepurposeofimprovingthemainLED

currentaccuracyandundervoltagethresholdaccuracy.Addinga0.1uF,capacitormayalsohelpwiththispurpose.



IS31LT3135V1,IS31LT3135V2

DualCh.(Main/Sub)LEDDriverEvaluationBoardGuide

Integrated Silicon Solution, Inc. – http://www.issi.com 4

V2, 4/23/2012



Figure3:ComponentPlacement:TopLayerFigure4:PCBLayout‐TopLayer



 Figure5:ComponentPlacementGuide‐BottomLayer Figure6:BoardPCBLayout‐BottomLayer



anytimewithoutnotice.ISSI assumes noliabilityarisingoutoftheapplicationoruseofanyinformation,productsor servicesdescribedherein.

Customersareadvisedtoobtainthelatestversionofthisdevicespecificationbeforerelyingonanypublishedinformationandbeforeplacingorders

forproducts.IntegratedSiliconSolution,Inc.doesnotrecommend theuseof anyofitsproducts inlifesupportapplicationswherethefailureor

malfunctionoftheproductcanreasonablybeexpectedtocausefailureofthelifesupportsystemortosignificantlyaffectitssafetyoreffectiveness.

ProductsarenotauthorizedforuseinsuchapplicationsunlessIntegratedSiliconSolution,Inc.receiveswrittenassurancetoitssatisfaction,that:

a) theriskofinjuryordamagehasbeenminimized;

b) theuserassumeallsuchrisks;and

c) potentialliabilityofIntegratedSiliconSolution,Inc.isadequatelyprotectedunderthecircumstances.

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