創(chuàng)新節(jié)能LED背光解決方案11 23 11yaeger

InnovativePowerSavingLEDBacklightSolutionsforMediumSizeDisplays

1JeremyYaegerNov23,2011Overview

LP85xxFamilyofLEDDriversTargetApplicationsFeatureComparisonEfficiencyDiscussionKeyFeaturesListPartbyPartFeatureExplanationTPS611xxFamilyofLEDDriversFeatureComparisonDetailedFeatureExplanation2LP85xxFamilyofLEDDrivers3TargetApplicationsNotebookTabletLP85504.5V-22VVIN2.7VVBATMIN(With5VExtBias)40V,6-Ch,50mA/ChIIC/PWMControlLP85534.5V-22VVIN2.7VVBATMIN(With5VExtBias)40V,4-Ch,50mA/ChIIC/PWMControl1.8VI/OSupportLP85524.5V-22VVIN2.7VVBATMIN(With5VExtBias)40V,6-Ch,50mA/ChIIC/PWMControl1.8VI/OSupportLP85562.7V-20VVIN48V,2-6-Ch,50mA/ChIIC/PWMControlCABCSupport1.8VI/OSupportLP85434.5V-22VVIN40V,6-Ch,55mA/Ch7thindependentChALS/IIC/PWMControlCABCSupportLP85454.5V-22VVIN40V,6-Ch,55mA/Ch60V(Ext.FEToption)IIC/PWMControlMonitorLP85626-Ch60mA/ChannelUpto125VVLED30khzPWMoutputVSYNC;HSYNCDEVELOPMENTRELEASEDLP8545LP8550/524LP85xxFeatureComparisonPartsStringsVIN

Min(V)VOUTMax(V)PhaseShiftPWMHysteresis&BrightnessSlopeDitherAdaptiveDimming1.8VI/OSupportCABCOutputResolution(Bits)LP85436+14.54010(PWM)LP854562.7*,4.54013+3(PWM)LP855062.7*,4.54013+3(PWM)8-bitAnalogLP855262.7*,4.54013+3(PWM)8

(Analog)LP855342.7*,4.54013+3(PWM)8(Analog)LP855662.74813+3(PWM)12(Analog)LP8556-UnderDevelopment(Samples–Nov;RTMTarget-Q1CY12)*2.7VVINMinoperationrequires5Vauxiliaryrail(max10mA)5EfficiencyDiscussionMostimportantthinginbacklightdriver!Efficiencycanbedividedindifferentfactors:BoostefficiencySwitchingfrequency,externalcomponents,PFMmode,switchoptimization,etc.LEDDriverHeadroomHeadroomdependsonthedrivertopologyBoostvoltagecontrolaccuracyHowwellLEDVfarematchedQuiescentCurrentIqHowmuchlogicneeded,resolution,analogblockdesignetc.6EfficiencyBreakdownPowerLossvs.Brightness01020304050607080901001.23.1610203040506075100Brightness[%]Percentageoftotalloss[%]BoostLEDDriverLogicLDOBoostLEDDriverLogic7ReducingLEDCurrentSinkPowerLossLEDCurrentSinkStructureLEDcurrentsinkheadroommustbeabovecertainleveltomaintainthedesiredcurrent,thisvoltageiscalledsaturationvoltage(VSAT)VSATconsistofNMOSandResistorresistanceReducingVSATreduceslossBoostadaptivecontrolaccuracyoptimizestheactualsinkheadroomachievedinsystemBoostVoltageisautomaticallyadjustedtominimumrequiredvaluebasedonminimumdriverheadroom(Vsat+Eepromsetting)andLEDstringwithlargestLEDVfImpactofreducingVSATVREFVSATLEDdriverefficiencyBrightness[%]Efficiency[%]9596979899100020406080100Vsat=50mVVsat=150mVVsat=450mVCurrentMatchingaccuracyRise&FalltimeaccuracyMaximumstringcurrentIncreasedbiasingcurrentTradeofftoreducingVSAT8ReducingBoostPowerLossDominatingLossesImpactofdynamicallyoptimizingRDSONbasedonLoadIQlossesandCapacitorESRlosses0.05

Inductorlosses0.6VDiodelosses0.15

RDSONlossesSwitchinglossesIout(A)Powerloss(W)(A)0.000.050.100.150.2000.050.10.150.20.259091929394959600.20.40.60.81Iout(A)Efficiency[%]0.50Ohm0.15Ohm0.05Ohm9ReducingQuiescentCurrentLDO+LogicPowerLossLEDDriverBlockDiagramAddingSecondarySupplyMostoflossisduetohighdropoutacrossLDO(ExampleVIN=9V;VBIAS=5V)ImpactofusingSecondarySupply50556065707580859095110100Brightness[%]ElectricalEfficiency[%]InternalLDOExternal5VpowerrailElectricalEfficiencywith/without5Vpowerrail10KeyNeeds,KeyIP&BenefitsKeyNeedsKeyIP(Features)BenefitsLongerBatteryruntimeLowLEDdriverheadroom85%to90+%backlightefficiencyacrossmostusedbrightnessrange.*ProgrammableboostPWM/PFMswitchoverpointOptimizedefficiencyforanygiveninputvoltageProprietaryAdaptiveBrightnesscontrolLongerBatteryruntime(Reducedinputpower)*CABCandALSHigherorderpowersaving≤1.0%MinimumDutyCycleLowestbrightnesssettingfordarkambience*BetterVisualExperience≤1.5%StringCurrentMatchingHighlyuniformscreenbrightnessdownto1%brightnesssetting*Upto16bitsofprogrammableoutputresolutionwithDitherSmoothandTransparentbrightnessresponse*NoimpacttoefficiencyProprietaryPhaseShiftPWMSchemeFreeofAcoustic&Visual(Flicker/Waterfall)artifactDisplay*LowcostofownershipFullyprogrammablearchitectureSupportmanyPanelconfigurationswithoutchangingcomponents.TimetesteddesignRobustPerformance**KeyfeaturesthatwonTablet&NotebookdesignsatkeyOEMs11AdaptiveDimming

-AnalogandPWMcombineddimmingschemeHigherEfficacy&ResolutionSmoothBrightnessChangeArtifactFreeDisplayBrightnessUniformity12MoreEfficientLEDdimming

-AdaptiveDimmingSmoothBrightnessChangeArtifactFreeDisplayBrightnessUniformityLEDEfficacyimproveswhenLEDcurrentisreducedfrom20mAHigherEfficacy13WithPWMcontrolweareoperatingatonepointonlyAchievingHigherSystemEfficacy

-AdaptiveDimmingSmoothBrightnessChangeArtifactFreeDisplayBrightnessUniformityAdaptiveDimming:LeveragesLEDcharacteristicstouselessinputpowerforsamebrightness(Nits)EnableshigherresolutioninlowbrightnessregionEnablesminbrightnesssettingstobelower(<1%)HigherEfficacy14AchievingUniformBrightnessStringcurrentmatchingaccuracyisakeyparameter,especiallyatlowbrightnesssettingsLEDcurrentinallthestringsshouldnotvarybymorethan2to3%HereishowourdevicesperformCurrentMatchingAccuracy%SmoothBrightnessChangeArtifactFreeDisplayBrightnessUniformityHigherEfficacy15AchievingPleasingVisualResponse

SupportingSmoothbrightnesstransitionsTypicalBrightnessResponseAdvancedSlopeLinearSlopeAdvancedSlopeHumaneye“perceives”glitchlikeresponsewhenbrightnessissettlingAdvancedslopeeliminatesthisperceptionSmoothBrightnessChangeArtifactFreeDisplayBrightnessUniformityHigherEfficacy16Sloped(Smooth)BrightnessResponseIncreasingResolutionThroughDither

-SupportingSmoothBrightnessTransitionsTraditionalSchemeDitherBasedSchemeIncreasingresolutionmeansincreasingcoreclockwhichfurthermeanshigherIQ8bit10bit12bit2051.255MHzClock10MHzClock2.5kHz10LEDDriverPWMfrequency20MHzClock4080ClockLSB→Wanttoget12-bitresolutionbutwithonly10-bitbaseresolution→Weuse2-bitDither01ThisSequenceisrepeated....1011(2-bitDitheruses4cycles)Cycle1Cycle2Cycle3Cycle4SmoothBrightnessChangeArtifactFreeDisplayBrightnessUniformityHigherEfficacy17Example1

12BitPWM→10-bit+2-bitDither18Say,thedesiredoutputvalueis10011-11110-01Usingdither,twoboundary10bitvalues(10111-11110and10111-11111)areoutputinacertainsequencetoarriveataneffective(Averaged/Dithered)12bitvaluethatisequivalentto10111-11110-01Base10bitvalue

10111-11110isoutputthricefollowedby

10111-11111once,togeteffective10111-11110-01,Note:2-Bituses4Dithercycles3-Bituses8Dithercycles18Example(2)

12BitPWM→10-bit+2-bitDitherSameexampleasbeforebutnowwith,10111-11110-10as

desiredoutputvalueSametwoboundary10bitvalues(10111-11110and10111-11111)areusedBase10bitvalues

10111-11110and0111-11111arenowalternatedtogeteffective10111-11110-1019Example(3)

12BitPWM→10-bit+2-bitDitherSameexampleasbeforebutnowwith,10111-11110-11as

desiredoutputvalueSametwoboundary10bitvalues(10111-11110and10111-11111)areusedBase10bitvalue10111-11110isoncefollowedby10111-11111thrice,togeteffective10111-11110-11

20ArtifactFreeDisplay

UncouplingInput&OutputPWMSmoothBrightnessChangeArtifactFreeDisplayBrightnessUniformityHigherEfficacy21InputPWMDetector:InputPWMsignalissampledusingoscillatorclockandconvertedtodigitalbrightnessvalue.OutputfrequencyandresolutionnotlimitedbyinputPWMfromhost.OutputPWMGenerator:OutputPWMfrequencyisgeneratedbasedoffPLL(orOscillator)frequency.Fpwmisprogrammable,sonotlimitedbywhateverinputPWMfrequencyis.HigherOutputPWMfrequenciesreduceflickerandwaterfallnoiseartifactsOutputDutycycleresolutionbasedonPLL/Oscillatorfrequency(PLLisprogrammable)ArtifactFreeDisplay

PhaseShiftPWMSchemeChannel-1Channel-2Channel-3Channel-4Channel-5Channel-6fPWMStandardPWMSchemefPWMEffectiveFreq.=ChannelcountxfPWM=6xfPWMPhase-ShiftPWMSchemeNormalPWMMode(fLED=4.2kHz)PhaseShiftPWMMode(fLED=4.2kHz)EliminatesAudibleNoiseSmallerloadtransientsoutputLoadfrequency6timesnormalPWMfrequencyOtherBenefitsSmoothBrightnessChangeArtifactFreeDisplayBrightnessUniformityHigherEfficacy22LP8543

7-ChannelHigh-EfficiencyLEDBacklightDriverEVMavailableuponrequestFeaturesBenefitsIntegrated40VBoostconverterStringCurrentmatching:

2%PhaseShiftPWM(PS-PWM)driverOutputFreq/Resolution:Upto19Khz/10bitsUpto60mAperChannelOn-chipinputHysteresisandOutputBrightnessresponsecontrolIICorPWMinputforBrightnesscontrolPackage:24L4x4mm,LLP(QFN)Supports2or3Li-IonBatterysystemsLongerBatteryRuntime85to90+%efficiencyovertheusabledisplaybrightnessrange.UniformScreenBrightnessevenat1%settingLowoutputripple→EliminatesAudiblenoiseApplications10”to15”panelbacklighting23LP8543–UniqueFeaturesOnchipALSInterfaceandcontrolCompensationCurves(E.gLogarithmicProfile)7thChannelcanbeconfiguredforancillarylighting(sub-display)orformaindisplay24On-ChipALSProcessingALSFilterControlLP8543SupportsALSofLight-to-Frequencytype200Hzto200kHzNo50Hz/60HzflickeringSimpleto2-pininterface;ALSPoweredbyLEDDriverRangeCalibrationAgnostictoSensorsfromvariousvendors25ProgrammableBrightnessResponse8-bitinputBenefitsExtendeddimming(8bit→10bit),andsmoothdimmingtransitions.LogarithmicbrightnessresponsetomatchhumaneyeresponseBrightnessuniformityacrossdifferentpanellotsthroughcalibration0255x1x2y1y2y301023ProgrammedBrightnessResponseProgrammableCo-ordinates10-bitoutput26LP8545

6-ChannelHigh-EfficacyLEDBacklightDriversEVMavailableuponrequestFeaturesBenefitsIntegrated40VBoostconverterStringCurrentmatching:

2%PhaseShiftPWM(PS-PWM)driverOutputFreq/Resolution:Upto19Khz/10bitsUpto60mAperChannelOn-chipinputHysteresisandOutputBrightnessresponsecontrolIICorPWMinputforBrightnesscontrolOutputsynchronizationtoVSYNCOptionforexternalFETforupto60VBoostPackage:24L4x4mm,LLP(QFN)Supports1or2or3Li-IonBatterysystemsLongerBatteryRuntime85to90+%efficiencyovertheusabledisplaybrightnessrange.UniformScreenBrightnessevenat1%settingLowoutputripple→EliminatesAudiblenoiseEliminatesVisualartifacts(Flicker,Waterfall)Applications10”to22”panelbacklighting27LP8545–ForDifferentConfigurationsConfiguration1Configuration2Configuration3AdditionalFlexibilityLP8545LP8545LP8545LEDVoltage→40VCurrentperchannel→Upto55mALEDVoltage→Upto60VCurrentperchannel→Upto55mALEDVoltage→Upto60VCurrentperchannel→110mAProgrammabilitythroughIICFinetuneLEDCurrentwith8-bitcontrol(230uASteps)ConfigurePWMfreq.basedonpaneltyperesolutionupto~19.5khzConfigurablechannelcount(fordifferentpanelsizes)On-chipEEPROMConfigurationstorage28LP8550/52/53

-4/6ChannelHigh-EfficacyLEDBacklightDriversFeaturesBenefitsIntegrated40VBoostconverterVINrange:2.7V-22V1.8-3.3VI/OSupport(LP8552/53)AdaptiveBrightnessControlStringCurrentmatching:

2%PhaseShiftPWM(PS-PWM)driverOutputFreq/Resolution:Upto19Khz/16bitsUpto50mAperChannel4-Channels(LP8553)6-Channels(LP8550andLP8552)On-chipinputHysteresisandOutputBrightnessresponsecontrolOutputsynchronizationtoVSYNCHighlyflexibleProgrammableandsettableLEDcurrentProgrammableandsettablePWMO/PfreqIICorPWMinputforBrightnesscontrolPackage:25Bump2.5x2.5mm,0.5mmPitchMicroSMDSupports1or2or3Li-IonBatterysystemsLongerBatteryRuntimeUpto20%inputpowersavingscombinedwith85to90+%efficiencyovertheusabledisplaybrightnessrange.UniformScreenBrightnessevenat1%settingLowoutputripple→EliminatesAudiblenoiseEliminatesVisualartifacts(Flicker,Waterfall)Applications7”to15”panelbacklightingTablet,Notebook,andDigitalPhotoFramesInstrumentation/NavigationdisplaysLP855X29LP8556

1to6ChannelHigh-EfficacyLEDBacklightDriverSamplesAvailableNowRTM:Q1CY12FeaturesBenefitsIntegrated48VBoostconverter(312/625/1250kHz)VINrange:2.7V-22V(SingleRail)1.8-3.6VI/OSupportBrightnessControlOptionsPWM,Adaptive,PureAnalogCABCSupportStringCurrentmatching:

0.5%PhaseShiftPWM(PS-PWM)driverOutputFreq/Resolution:Upto39Khz/16bitsUpto50mAperChannelEdge-ratecontrolandspreadspectrumschemePackage:20Bump1.7x2.4mm,0.4mmPitchMicroSMDSupports1or2or3Li-IonBatterysystemsLongerBatteryRuntimeUpto20%inputpowersavingscombinedwith85to90+%efficiencyovertheusabledisplaybrightnessrange.UniformScreenBrightnessevenat1%settingLowoutputripple→EliminatesAudiblenoiseEliminatesVisualartifacts(Flicker,Waterfall)ProtectionfromEMIApplications7”to15”panelbacklightingTablet,Notebook,andDigitalPhotoFramesInstrumentation/Navigationdisplays30LP8556

-KeyFeatureListandBenefits1.7x2.4mm,0.4mmPitch,20BumpMicroSMDFEATUREBENEFITSingleRailsupportwith2.7VVINMINCostSavingHighEfficiencyDC/DCboostcontroller:Fourfrequencyoptions:312/625kHz/1250kHzOptimumEfficiencyforagivenconfigurationOptionforSmallerInductorAdaptiveDimmingSchemeReducedInputPowerforagivenBrightnessEnablesHigherresolution(inthelowbrightnessrange)FlexiblePhaseShiftSchemeConfigurableChannel-AvoidAudibleNoise(ReducedOutputRipple)Upto12truebits+Upto3bitsusingditheringSmoothBrightnesstransitionsFinerStepsforManualcontrolUpto30kHzPWMoutputfrequencySupportsHigherResolution(BetterDisplayqualityforLargeScreenSizes)ProgrammableEdgerateControl&SpreadspectrumSchemeImprovedEMIperformanceProgrammableOVPthresholdsCostSaving(EnablesExternalComponentstobeoptimizedforagivenapplication)31ContentAdjustableBacklightControlI2CBrightnessRegisterControlandPWMBrightnessControlcanbemultipliedtogethertosetthebacklightbrightness.ThiscanbedonebeforeorafterCurveshaperblock(previousslide).InLP8550systemthismultiplicationwasnotpossibleandCURRENT[7:0]wasusedtoscalepeakstringcurrentinadditiontoPWMbrightnessinput.Thismean“userbrightness”couldnotuseshapingblock(smoothhardwaredimming).Also,aSCALE[2:0]registerwasaddedtoselectmaxstringcurrentbeforeCURRENT[11:0]registerisapplied(insteadoffixed30mAmaxcurrentintheLP8550).32CABCImprovementsinLP8556Suddenbrightnesschanges(CABC)andlargeLEDloadscan,insomecases,causetheboostoutputvoltagetodroop.IfthedroopislargeenoughthiscancausetheLEDdriverstosaturate.TheLP8556canuseaboostvoltage“jump”functiontoincreasetheboostvoltageby(0.5v,1v,2v,4v)whenitdetectsalargebrightnesschange(CABC).Thispreventstheboostoutputfromdroopingandfollowingthebrightnesschangetheboostvoltagewillbeadjustedbacktotheoptimallevelforefficiency.BoostJumpDisabledBoostJumpEnabledPWMInputBoostOutLEDDriverHeadroomLEDCurrentPWMInputBoostOutLEDDriverHeadroomLEDCurrent33TPS611xxFamilyofLEDDrivers34TPS611xxFeatureComparison35TPS61180/1/2

40VBoostRegulatorwith6CurrentRegulatorsin3x3x0.8mmQFNpackage

5-Vto24-VinputvoltagerangeIntegrated1.5A/40VPWMSwitch1.0/1.3-MHzswitchingfrequencyAdaptiveboostoutput4.7uHinductorand2.2uFoutputcapacitorSixcurrentsinkof25mAUpto10WLEDinseries2%currentmatchingandaccuracy100:1PWMdimmingrangeDriverforinput/outputisolationPFET16L3mmx3mmx0.8Thin-QFNpackageIntegratedpowerFETin3x3QFNpackageSmallVoutrippleduringPWMdimmingInput/outputisolationforshortcircuitprotection

NotebookLCDbacklightUpto15.4”displaybacklight

36TPS61181A

40VBoostRegulatorwith6CurrentRegulatorsin3x3x0.8mmQFNpackage

4.5-Vto24-VinputvoltagerangeIntegrated1.5A/40VPWMSwitch1.0MHzswitchingfrequencyAdaptiveboostoutput4.7uHinductorand2.2uFoutputcapacitorSixcurrentsinkof30mA20VmaxratingENandDCTRLpinUpto10WLEDinseries2%currentmatchingandaccuracy100:1PWMdimmingrangeDriverforinput/outputisolationPFET16L3mmx3mmx0.8Thin-QFNpackageIntegratedpowerFETin3x3QFNpackageSmallVoutrippleduringPWMdimmingInput/outputisolationforshortcircuitprotection

NotebookLCDbacklightUpto15.4”displaybacklight

37TPS61180/1/2

UsedforTabletPCswithsingleLi-IonbatteryIfthesourceisasingleLi-Ionbattery,theTPS6118xfamilycanbeadjustedin2ways:1.-Havingalreadya5Vrailinthesystem2.-BoostingfromLi-Ionto5Vwithachargepumptoavoidextrainductor.Forfurtherinformationaboutthisapplication,pleasecheckthefollowingappnoteTPS61181One-CellBatteryApplicationforTabletPCBacklight

38TPS61183

40VBoostRegulatorwith6CurrentRegulatorsin4x4x0.8mmQFNpackage

4.5-Vto24-VinputvoltagerangeIntegrated2.5A/40VPWMSwitch300kHz~1MHzprogrammableswitchingfrequencyAdaptiveboostoutputWidePWMdimmingfrequency

100:1brightnessrationat22kHz10000:1brightnessrationindirectPWM200HzSixcurrentsinkof30mA20VmaxratingENandDCTRLpinUpto10WLEDinseries1.5%currentmatchingandaccuracyDriverforinput/outputisolationPFET20L4mmx4mmx0.8Thin-QFNpackageIntegratedpowerFETin4x4QFNpackageSmallVoutrippleduringPWMdimmingInput/outputisolationforshortcircuitprotection

NotebookLCDbacklightUpto15.4”displaybacklight

39TPS61185--Highestefficiency96%Highefficiencyiskey:PercentageoftotalpowerbudgetdedicatedtobacklightishighNotebooksupto40%,smartphonesortabletPCs,upto60%Keepssystemtemperaturedown,criticalforliquidcrystal.25mAperstring40TPS61185--Highestaccuracy1%Highaccuracyisneeded:Improvesdisplayquality-ConsistentbrightnessacrossallLEDstringsprovidinganimprovedpicture1%accuracyaveragecurrentbetweenstrings4142

NotebookLCDdisplaybacklightTPS61195

WLEDDriverforNotebookswithPWMandSMBuscntrolinterfaceTPS61195EVM-460Best-in-classcurrentmatching–1%typ.,IntegratedLoopcompensation,

SMBusdimmingbrightnessInterface.600kHzto1MHzprogrammableswitchingfrequencyupto20kHzDirectPWMDimmingFrequencyImprovesdisplayquality-ConsistentbrightnessacrossallLEDstrings.Internalcompensationeliminates3externalcomponentsandreducesdesigneffort.256dimmingstepsAllowsoptimizationofefficiency,boardspaceandEMIcharacteristics.42TPS61195--varietyofdimmingoptionsSEL1andSEL2determinetypeofdimmingAnalogdimmingDirectPWMdimmingfrequencyExternalPWMsignalAllowswiderangeofdimmingduetoflexibledutycycleProgrammablePWMdimmingfrequencyor‘nodelay’dimming ExternalRfixesPWMsignalsettingonelevelofdimmingDigitaldimminginterface(SMBus):DirectPWMdimmingProgrammablePWMdimmingDigitalInterfaceSMBus43TPS61187

40VBoostRegulatorwith6CurrentRegulatorsin4x4x0.8mmQFNpackage

4.5-Vto24-VinputvoltagerangeIntegrated2A40V

FET6channels30mA

MaximumWLEDcurrent.

38VMaximumoutput(39VOVP)

Adjustable300KHz~1.2MHzswitchingfrequencyPWMinputbrightnesscontrol(100Hzto22kHz)WidefrequencyrangePWMoutputdimming100Hzto22kHzforautophaseshiftmode