244406_PAM_PAM2842

HighPowerLEDDriver

Features

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Description

ThePAM2842isahighpowerLEDdriver,capableofdrivingupto10highpowerLEDsinseries.ThePAM2842supportsbuck,boostandsepictopology.

ThePAM2842featuresovercurrentprotection,overvoltageprotection,undervoltagelockoutandovertemperatureprotection,whichpreventthedevicefromdamage.

LEDdimmingcanbedonebyusingaPWMsignaltotheCOMPpin.

ThePAM2842isavailablein40-PinQFN6x6andTSSOP-20packages.

OutputPowerupto30WChipEnablewithSoft-startAnalogandPWMDimmingPeakEfficiencyupto97%LowQuiescentCurrent

SwitchingFrequencyAdjustableSupportBuck/Boost/SepicTopologyOverCurrentProtectionOverVoltageProtectionThermalProtectionUVLO

TinyPb-FreePackages:

40-PinQFN6x6andTSSOP-20

Applications

nHomeLighting

nAutomotiveLightingnMonitorBacklighting

TypicalApplicationCircuit

BoostwithLowSideCurrentSense

Vin1μFL1BoostwithHighSideCurrentSense

Vin1μFL133μH0.14Ω33μHPGNDPGNDHVINENSWSWOVVDD-5V1μF1kΩ10nF10μF0.14Ω1μF130kΩ430kΩPGNDPGNDHVIN15kΩSWSWOVVDD-5V1μF1kΩ10nF430kΩVDD-DR10μF1μF130kΩPAM2842COMPSense+Sense-EN15kΩPAM2842COMPSense+Sense-VDD-DRRTAGNDRTAGNDPowerAnalogMicroelectronics,Inc

www.poweranalog.com

09/2008Rev1.1

1

PAM2842

HighPowerLEDDriver

TypicalApplicationCircuit

Buck/Boost(Sepic)withLowSideCurrentSense

Vin1μFL1Buck/Boost(Sepic)withHighSideCurrentSense

Vin1μFL110μF56kΩ0.14Ω47μH47μHL247μH47μHL2PGNDPGNDHVINEN10μF1μF130kΩSWSWOVVDD-5V1μF220kΩPGNDPGNDHVIN12kΩ10nF10μF1μF0.14Ω130kΩSWSWOVVDD-5V1μF220kΩ12kΩ10nFPAM2842COMPSense+Sense-ENVDD-DR1kΩPAM2842COMPSense+Sense-VDD-DR1kΩRTAGNDRTAGNDBuckwithHighSideCurrentSense

Vin0.14Ω

1μF10μFPGNDPGNDHVINENSWSWOVL47μH1nFNCVDD-5VVDD-DR10μF1μF130kΩPAM2842COMP1kΩ100nF12kΩRTAGNDSense+Sense-PowerAnalogMicroelectronics,Inc

www.poweranalog.com

09/2008Rev1.1

2

PAM2842

HighPowerLEDDriver

BlockDiagram

VDD_5V

HVINCOMP

OVSWSWLDO1Comparator-PWM+PWMLogicAndDriverLDO2VDD-DRΣ100mVReferenceCS+-Sense+Sense-EN+GM-RampGeneratorFBShutdownAndSoft-startAdjustableOscillatorAGNDRTPGNDPGNDPowerAnalogMicroelectronics,Inc

www.poweranalog.com

09/2008Rev1.1

3

PAM2842

HighPowerLEDDriver

PinConfiguration&MarkingInformation

TopView6mm*6mmQFN

NCNCNCNCNCNCNCNCNCNCTOPViewTSSOP-20

40PGNDPGNDPGNDPGNDPGNDPGND

NCHVINEN

393837363534333231302928SWSWSWSWSWSWNCOVNCVDD_5V

PGNDPGNDPGNDPGNDHVINEN

12345671020191817161514131211NCSWSWSWOVVDD_5VCOMPSense+Sense-

123456710

PAM2842XXXYWWLLPAM2842XXXYWWLL

27262524232221

VDD-DR

RT

AGNDPGND

PGNDVDD-DR

13AGND14Sense-15Sense+16NC17COMP18NC19NC20NCX:InternalCodeY:YearWW:Week

LL:InternalCode

11NCRT12PinNumberQFN6x6-401-6101213141517212325-307,11,16,18-20,22,24,31-40TSSOP-201,2,3,4,10,11567121314151617,18,1920NamePGNDHVINENVDD-DRRTAGNDSense-Sense+COMPVDD_5VOVSWNCDescriptionPowerGroundInputChipEnable,ActiveHighInternalLDOOutputFrequencyAdjustmentPinAnalogGroundSenseresistor-Senseresistor+CompensationNodeInternalLDOOutputOverVoltageDrainofMainSwitch.NoConnectPowerAnalogMicroelectronics,Inc

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09/2008Rev1.1

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PAM2842

HighPowerLEDDriver

AbsoluteMaximumRatings

Thesearestressratingsonlyandfunctionaloperationisnotimplied.Exposuretoabsolutemaximumratingsforprolongedtimeperiodsmayaffectdevicereliability.Allvoltagesarewithrespecttoground.

SupplyVoltage.............................................40VOutputCurrent................................................1AI/OPinVoltageRange.........GND-0.3VtoVDD+0.3V

StorageTemperature.....................-40OCto125OCMaximumJunctionTemperature..................150OCSolderingTemperature.......................300OC,5sec

RecommendedOperatingConditions

SupplyVoltageRange.........................5.5Vto40V

OO

OperationTemperatureRange..........-40Cto85C

JunctionTemperatureRange..........-40Cto150C

O

O

ThermalInformation

ParameterThermalResistance(JunctiontoCase)ThermalResistance(JunctiontoAmbient)SymbolθJCθJAPackageTSSOPQFN6mm*6mmTSSOPQFN6mm*6mmMaximum207.6*9018.1*°C/WUnit*TheExposedPADmustbesolderedtoathermallandonthePCB.

PowerAnalogMicroelectronics,Inc

www.poweranalog.com

09/2008Rev1.1

5

PAM2842

HighPowerLEDDriver

ElectricalCharacteristic

PARAMETERInputVoltageRangeENA=high(noswitching)ENA=high(1Mswitchingfrequency)QuiescentCurrentENA=high(500kswitchingfrequency)ENA=high(200kswitchingfrequency)ENA=lowFeedbackVoltage,LowSideFeedbackVoltage,HighSideLEDCurrentLineRegulationLEDCurrentLoadRegulationLDOStageVDD_5VVDD_5Vcurrent_limitVDD_5VUVLOThresholdVDD_5VUVLOHysteresisVDD_DRVDD_DRcurrent_limitVDD_DRUVLOThresholdVDD_DRUVLOHysteresisSwitchRdsonSwitchCurrentLimitSwitchLeakageCurrentRTVoltageSwitchingFrequency*RRT=71kΩRRT=30kΩRRT=71kΩRRT=180kΩFSW=1MHzMinDutyCycleFSW=500kHzFSW=200kHzMaxDutyCycleVcSourceCurrentVcSinkCurrentLowSideSenseHighSideSenseFeedbackvoltage=0Feedbackvoltage=01.1800k400160NoswitchingNoswitchingNoswitchingNoswitchingNoswitchingNoswitchingNoswitchingNoswitchingSwitchStageVDD_5V=5V0.13.5501.21M5002001052.59510030301.31.2M600240ΩAμAVHzkHzkHz%%%%%μAμA4.5143.74.5143.75744.02005504.02005.5904.35.5904.3VmAVmVVmAVmVVFB=VSENSE+-AGND,VSENSE-=AGNDVFB=VSENSE+-VSENSE-IO=350mA9595VEN=VDD=24V,1Wx10LEDs,TA=25°C,unlessotherwisenoted.ConditionsMin5.51631.651001000.021.010105105TypMax402UnitsVmAmAmAmAμAmVmV%/V%1210*SwitchingFrequencyFSW=,referencevalue24´(RRT+12k)PowerAnalogMicroelectronics,Inc

www.poweranalog.com

09/2008Rev1.1

6

PAM2842

HighPowerLEDDriver

ElectricalCharacteristic

PARAMETEROVthresholdVoltageOVHysteresisThermal-ShutdownThermal-ShutdownHysteresisControlInterfaceENHighENLow1.50.4VVVEN=VDD=24V,1Wx10LEDs,TA=25°C,unlessotherwisenoted.

ConditionsFaultProtection1.11.270150301.3VmV°C°CMinTypMaxUnitsPowerAnalogMicroelectronics,Inc

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09/2008Rev1.1

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PAM2842

HighPowerLEDDriver

TypicalPerformanceCharacteristic

1.EfficiencyvsInputVoltage(Po=30W,10X3WLEDs)

Boostmode,VEN=VDD=24V,3WLED,Fsw=200kHz,TA=25°C,unlessotherwisenoted.

2.ShutdownCurrentvsInputVoltage

65ShutdownCurrent(uA)98%

97%

43210

Efficiency96%

95%

94%

93%

10

15

20

InputVoltage(V)

25

30

05101520253035

InputVoltage(V)

3.QuiescentCurrentvsInputVoltage

1.81.6

800700

4.OutputCurrentvsInputVoltage(10X3WLEDs)

QuiescentCurrent(mA)1.41.210.8

Switching0.6

0

5

10

15

20

25

30

35

InputVoltage(V)

NoSwitchingOutputCurrent(mA)600500400300200100010

15

20

InputVoltage(V)

25

30

LowsideCurrentsenseHighsideCurrentsense800750OutputCurrent(mA)5.OutputCurrentvsTemperature(VIN=12V,Load=10X3WLEDs)

700650600550500450400

0

20

40

60

80

100

AmbientTemperature(℃)

PowerAnalogMicroelectronics,Inc

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09/2008Rev1.1

8

PAM2842

HighPowerLEDDriver

TypicalPerformanceCharacteristic

Fsw=300kHz,TA=25°C,unlessotherwisenoted.

5.OutputCurrentvsInputVoltage(Sepicmode,1WLED),

6.EfficiencyvsInputVoltage(Sepicmode,1WLED),

400350OutputCurrent(mA)90%%88%87%

300

Efficiency4*1W3*1W1*1W2*1W2502001501005005

10

15

20

InputVoltage(V)

86%85%84%83%82%81%

5

7

9

11

13

15

17

19

InputVoltage(V)

3*1W1*1W4*1W2*1W0.80.7

7.OutputCurrentvsInputVoltage(Buckmode,3WLED),

100%95%90%

8.EfficiencyvsInputVoltage(Buckmode,3WLED),

OutputCurrent(A)0.6

Efficiency0.50.40.30.20.105

10

15

20

25

30

35

40

InputVoltage(V)

85%80%75%

1*3W2*3W3*3W70%

5

10

15

20

25

30

35

40

InputVoltage(V)

400350

9.LEDCurrentvsDutyCycle

(PWM=100Hz,inDimmingState)

10.StartupandShutdown

LEDCurrent(mA)3002502001501005000

20

40

60

80

100

DutyCycle(%)

VoutENVcomp

PowerAnalogMicroelectronics,Inc

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09/2008Rev1.1

9

PAM2842

HighPowerLEDDriver

ApplicationInformation

TopologySelection

Whenmaximumpowersupplyvoltageisbelowthanminimumloadvoltage,selecttheboosttopology.Whenminimumpowersupplyvoltageishighthanmaximumloadvoltage,selectbucktopology.Whenloadvoltagerangeissmallandbetweenthepowersupplyvoltage,selectsepictopology.

Table-1:VoltageconditionVsTopology

Forthelargepowerapplication,ifchoseDCM,thepeakcurrentwillbeverylarge,itwillhavegreatelectricalstressonthecomponents,sowechoseCCM.

WhenworkinCCMmode,areasonableripplecurrentischosento

ΔIL=0.4ILFortheboosttopology,

ConditionVinmaxIO1-D

Vinmin>VomaxVoÌVinInductorSelection

VO-VIN

VO

DIL=

VIN(VO-VIN)LFVO

Theinductance,peakcurrentrating,seriesresistance,andphysicalsizeshouldallbeconsideredwhenselectinganinductor.Thesefactorsaffecttheconverter'soperatingmode,efficiency,maximumoutputloadcapability,transientresponsetime,outputvoltageripple,andcost.

Themaximumoutputcurrent,inputvoltage,outputvoltage,andswitchingfrequencydeterminetheinductorvalue.Largeinductancecanminimizesthecurrentripple,andthereforereducesthepeakcurrent,whichdecreasescorelossesintheinductorandI2Rlossesintheentirepowerpath.However,largeinductorvaluesalsorequiremoreenergystorageandmoreturnsofwire,whichincreasesphysicalsizeandI2Rcopperlossesintheinductor.Lowinductorvaluesdecreasethephysicalsize,butincreasethecurrentrippleandpeakcurrent.Findingthebestinductorinvolvesthecompromisesamongcircuitefficiency,inductorsize,andcost.

Whenchoosinganinductor,thefirststepistodeterminetheoperatingmode:continuousconductionmode(CCM)ordiscontinuousconductionmode(DCM).WhenCCMmodeischosen,theripplecurrentandthepeakcurrentoftheinductorcanbeminimized.Ifasmall-sizeinductorisrequired,DCMmodecanbechosen.InDCMmode,theinductorvalueandsizecanbeminimizedbuttheinductorripplecurrentandpeakcurrentarehigherthanthoseinCCM.

D:dutycycle,Io:outputcurrent,F:switchingfrequency.

Fromaboveequationwecangettheinductance:

2

2.5VIN(VO-VIN)L=2

FIOVO

Theinductor'scurrentratingshouldbehigherthan

IL+

DIL2

VOVIN

Forthebucktopology,IL=IO

D=

DIL=

(VIN-VO)VO

LFVIN

so

L=

2.5VO(VIN-VO)

FIOVIN

Forthesepictopology,L1=L2

D

IL1=IO

1-D

IL2=IO

D=

VOVIN+VO

PowerAnalogMicroelectronics,Inc

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09/2008Rev1.1

10

PAM2842

HighPowerLEDDriver

DIL=

VINVO

LF(VIN+VO)

Theripplevoltageis

Choseso

ΔIL=0.4IL1

2

2.5VIN

L=

FIO(VIN+VO)

IODFCS

Thevoltageratingmustbehigherthaninputvoltage.

DVCs=

BecausetheCscapacitorwillflowthelargeRMScurrent,sothistopologyissuitableforsmallpowerapplication.DiodeSelection

PAM2842isahighswitchingfrequencyconverterwhichdemandshighspeedrectifier.It'sindispensabletouseaSchottkydioderatedat3A,40VwiththePAM2842.UsingaSchottkydiodewithalowerforwardvoltagedropisbettertoimprovethepowerLEDefficiency.

Inboosttopology,thevoltageratingshouldbehigherthanVoutandinbucktopology,thevoltageratinghigherthanVin,thepeakcurrentis

CapacitorSelection

AninputcapacitorisrequiredtoreducetheinputrippleandnoiseforproperoperationofthePAM2842.Forgoodinputdecoupling,LowESR(equivalentseriesresistance)capacitorsshouldbeusedattheinput.Atleast10μFinputcapacitorisrecommendedformostapplications.AndclosetheICVin-Pinweshouldaddabypasscapacitor,usuallyusea1μFcapacitor.

Aminimumoutputcapacitorvalueof10μFisrecommendedundernormaloperatingconditions,whilea22μForhighercapacitormayberequiredforhigherpowerLEDcurrent.AreasonablevalueoftheoutputcapacitordependsontheLEDcurrent.Thetotaloutputvoltageripplehastwocomponents:thecapacitiveripplecausedbythecharginganddischargingontheoutputcapacitor,andtheohmicrippleduetothecapacitor'sequivalentseriesresistance.TheESRoftheoutputcapacitoristheimportantparametertodeterminetheoutputvoltagerippleoftheconverter,solowESRcapacitorsshouldbeusedattheoutputtoreducetheoutputvoltageripple.ThevoltageratingandtemperaturecharacteristicsoftheOutputcapacitormustalsobeconsidered.Soavalueof10μF,50Vvoltageratingcapacitorischosen.

Considerfromdischargeaspect:IxΔt=CxΔVInboostandsepictopology,CO=Inbucktopology,CO=

IDMAX=IL+

DIL2

insepictopology,thevoltageratingshouldbehigherthanVin+Vout,thepeakcurrentis

IDMAX=IL1peak+IL2peak

TheaveragecurrentofthediodeequalstoIo.Workfrequencyselection

PAM2842workingfrequencyisdecidedbyresistorconnecttotheRTpin,itcanbecalculatedbyfollowequation:

1012

FSW=(Hz)

24´(RT+12K)Fromtheequations,wecanseewhenworkingfrequencyishigh,theinductancecanbesmall.It'simportantinsomesizelimitapplication.Butweshouldknowwhentheworkingfrequencyishigher,theswitchinglossishighertoo.Wemustpayattentiontothermaldissipationinthisapplication.

MethodsforSettingLEDCurrent

TherearetwomethodsforsettingandadjustingtheLEDcurrent:1)Rsenseonly

2)PWMsignalwithexternalcomponents

a)UsetheCOMPpinb)UsetheSensepin

IODFVRIPPLE

IO(1-D)FVRIPPLE

VRIPPLE:Outputvoltageallowableripple.Considerfromequivalentseriesresistance:

Vripple-esr=Ico.ripplexCoesr

Insepictopology,thereisaseriescapacitorCsbetweenL1andL2(seeapplicationschematic),itflowsthecurrent:

VOICs(RMS)=IOVINPowerAnalogMicroelectronics,Inc

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09/2008Rev1.1

11

PAM2842

HighPowerLEDDriver

lMethod1:LEDCurrentSettingwithResistor

Itmaybegeneratetheaudiblenoiseinthisdimmingcondition.

lMethod3:LEDCurrentSettingwithPWM

Rsense

ThemostbasicmeansofsettingtheLEDcurrentisconnectingaresistorbetweenRsense+andRsense-.TheLEDcurrentisdecidedbyISETResistorRsense.

ILED=0.1/Rsense

Forflowingthelargecurrent,mustpayattentiontopowerdissipationontheresistor.

Rsensehastwopositiontoselect:highsidecurrentsenseandlowsidecurrentsense.Inbucktopologyitjusthashighsidecurrentsense.InothertopologywerecommenduselowsidecurrentsenseforeasierPCBlayout.SignalUsingCOMPPinlMethod2:LEDCurrentSettingwithPWMSignalusingSensePin

ThismethodisturnPWMsignaltoDCvoltage,theoutputcurrentcanbeadjusted.BecausetheLEDcurrentisaadjustableDCvalue,itwillcauseLEDcolordrift.

Lowsidecurrentsenseandhighsidecurrentsensecircuitisdifferent.PleaseseeFigure2and3.Itusetheinternalreferencevoltage,soPWMdimmingsignalvoltageisnotconsidered,justmeettherequestoftheMOSFETdrivingvoltage.

VDD_5VR1D1R2R3Sense+R4RTNThiscircuitusesresistorRsensetosettheonstatecurrentandtheaverageLEDcurrent,thenproportionaltothepercentageofoff-timewhentheCOMPpinislogichigh.Hereuseainvertcomponent2N7002(Q1)toisolateandinvertthePWMsignal(SeeFigure1).PWM-DIMQ1C1C2RSenseFigure2.PWMDimmingUseSensePininLowSideCurrentSensePAM2842COMPQ12N7002PWMsignalTonToffQ1R1D1Sense+VDD_5VR3Sense-Q2RSenseVoFigure1.PWMDimmingUseCOMPPinAverageLEDcurrentisapproximatelyequalto:TIIAVG=OFFLEDTON+TOFFAlso,therecommendedPWMfrequencyisbetween100Hzand200Hz.Frequency<100HzcancausetheLEDstoblinkvisibly.AstheCOMPpinconnectstoacapacitor,itneedsrisetime.Iffrequency>200Hz,theaverageLEDcurrentwillhavealargeerrorwhendutycycleissmall(<50%).PWM-DIMR5C1R4Figure3.PWMDimmingUseSensePininHighSideCurrentSenseTheRCfilter(R1,R2,C1,C2)valueisdecidedbydimmingfrequency,thedividerresistor(R3,R4)isdecidedbydimmingrange.BecausefinaladjustedisaDCvalue,thismethodcanavoidaudiblenoiseeffectivelyandachievebetterEMIperformancethanthesecondmethod.PowerAnalogMicroelectronics,Incwww.poweranalog.com09/2008Rev1.112PAM2842

HighPowerLEDDriver

SettingtheOutputLimitVoltage

TheOVpinisconnectedtothecentertapofaresistivevoltagedividerfromthehigh-voltageoutputtoground(seeapplicationschematic).

R

VOUT-Limit=VOV(1+UP)

RDOWNTherecommendprocedureistochooseR3=360KandR4=12KtosetVout_limit=37.2V.Inboostandsepiccircuit,whenLEDopenornoload,thecircuitwillhavenofeedback,ifnoothermeasurebetakentheswitchvoltagewillbeveryhighanddamagetheswitch,sothisOVpinmustbesetcarefully.

Inbuckcircuit,theswitchvoltageisalwayssmallthaninputvoltage,sotheOVpinsettingisnotimportantinthiscondition.

ThisOVpinisusedtolimitoutputvoltagetoavoidbreakdownoftheswitchotherthantoregulateoutputvoltage.Thesettingvaluemustkeeptheswitchvoltagebelow40V.

Insepiccircuit,onemustnoticethattheswitchvoltageequalsVin+Vo.

ThisOVpinhasahysteresisvoltagedetectfunction,notlatch-upfunction,sooutputvoltagewillhaveaovershootwhennoloadorloadworkingvoltageishighthansettinglimitvoltage.Ifthecomponentparameternotmatchappropriately,theovershootvoltagewillbetoohighandcandemagetheswitch.

Severalmethodscandecreasetheovershootvoltage:(1)Addasmallcapacitor(<100pF)parallelwiththeupdividerresistor(SeeFigure4).(2)Useexternalzenertoclamptheoutputpeakvoltage(SeeFigure5).

VoutVoutCOMPZENER

QRFigure5:UseExternalZener

Note:Theoutputlimitvoltagemustbesethigherthanworkingoutputvoltagebyapropervalue,oritwillworkabnormalinlowtemperatureorsomeotherconditions.ShortLEDFunction

PAM2842isaconstantcurrentdriver.WhenoneormoreLEDshorted,thecircuitwillstillwork,theoutputvoltageisdecidedbyLEDnumbers.Inboosttopology,makesuretheoutputvoltageishigherthaninputvoltage;otherwisetheunlimitedcurrentwilldirectlygothroughsupplytoLEDanddamagetheLED.PowerDissipation

AsPAM2842integratesapowerMOSFET,thepowerdissipationmustbeconsidered.ToaMOSFETthepowerlossincludes5sections,turnonloss,turnoffloss,conductionloss,drivelossandoutputcapacitorCossloss.

1

Pturn-on=Iturn-onVOUTTrf

2

1

Pturn-off=Iturn-offVOUTTrf

2

2

PRDson=IRMSRDSon

PDrive=QgUDrivef

R3CfOV

PCoss=

12

COSSVOUTf2

R4PSwitch=Pturn-on+Pturn-off+PRDSon+Pdrive+PCoss

DT=qjaPswitch

Tr:switchrisetime.Tf:switchfalltime.UDrive:gatedrivevoltage.θjaisrelativewithICpackage,heat-sinkareaandairflowconditionetc.

Figure4:addforwardcapacitor

PowerAnalogMicroelectronics,Inc

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09/2008Rev1.1

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PAM2842

HighPowerLEDDriver

AbovedescriptiondoesnotconsidertheICcontrolpower,sothetotalpowerwillbemorethancalculatedvalue.

PAM2842hasover-temperatureprotection.Whenjunctiontemperatureisover150°C,itwillshutdownandautorestartwhenjunctiontemperaturedecreasebelow120°C.

Inhightemperaturecircumstanceapplication,onemustpayattentiontoheatdissipation,oritwillshutdownandrestart.Itisrecommendedtouseexternalheat-sinkandplacedneartotheICsurface.

PCBLayoutGuidelines

CarefulPCBlayoutisimportantfornormaloperation.UsethefollowingguidelinesforgoodPCBlayout:(BOOST)

1)Minimizetheareaofthehighcurrentswitchingloopoftherectifierdiodeandoutputcapacitortoavoidexcessiveswitchingnoise.2)Connecthigh-currentinputandoutputcomponentswithshortandwideconnections.Thehigh-currentinputloopgoesfromthepositiveterminaloftheinputcapacitortotheinductorandtheSWpin.Thehigh-currentoutputloopisfromthepositiveterminaloftheinputcapacitorthroughtheinductor,rectifierdiode,andpositiveterminaloftheoutputcapacitors,reconnectingbetweentheoutputcapacitorandinputcapacitorgroundterminals.Avoidusingviasinthehigh-currentpaths.Ifviasareunavoidable,usemultipleviasinparalleltoreduceresistanceandinductance.3)

Createagroundisland(PGND)consistingof

TSSOP-20BOOST

theinputandoutputcapacitorgroundandPGNDpin.Connectallthesetogetherwithshort,widetracesorasmallgroundplane.Maximizingthewidthofthepowergroundtracesimprovesefficiencyandreducesoutput-voltagerippleandnoisespikes.Createananaloggroundisland(AGND)consistingoftheoutputvoltagedetection-dividergroundconnection,theSense-pinconnection,VCC-5VandVCC-drivercapacitorconnections.Connectthedevice'sexposedbacksidepadtoPGND.Makesurenootherconnectionsbetweentheseseparategroundplanes.

4)Placetheoutputvoltagesetting-dividerresistorsasclosetotheOVpinaspossible.Thedivider'scentertraceshouldbekeptshort.AvoidrunningthesensingtracesnearSWPin.

5)PlacetheVINpinbypasscapacitorasclosetothedeviceaspossible.ThegroundconnectionoftheVINbypasscapacitorshouldbeconnecteddirectlytoGNDpinswithawidetrace.

6)MinimizethesizeoftheSWnodewhilekeepingitwideandshort.KeeptheSWnodeawayfromthefeedbacknode.Ifpossible,avoidrunningtheSWnodefromonesideofthePCBtotheother.

7)Forthegoodthermaldissipation,PAM2842hasaheatdissipatepadinthebottomside,itshouldbesolderedtoPCBsurface.Asthecopperareacannotbelargeinthecomponentside,wecanusemultipleviasconnectingtoothersideofthePCB.

8)RefertotheexampleofaPAM2842Evaluationboardlayoutbelow.

QFN6x6-40BOOST

PCBLayoutExample

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09/2008Rev1.1

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PAM2842

HighPowerLEDDriver

OrderingInformation

PAM2842XXXShippingNumberofPinPackageType

PartNumberPAM2842RGRPAM2842TJRPackageTSSOP-20QFN6X6-40Shipping1,000units/Tape&Reel1,000units/Tape&ReelPowerAnalogMicroelectronics,Inc

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09/2008Rev1.1

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PAM2842

HighPowerLEDDriver

OutlineDimensions

TSSOP-20

SYMBOL

AA1A2DE1ELRR1

MIN.-0.0250.806.44.36.20.450.090.09

NOM.--0.906.54.46.40.60--

MAX.1.200.1001.056..56.60.75--

SYMBOL

bb1cc1θL1eN

MIN.0.190.190.090.090º

NOM.-0.22---1.0REF0.65BSC

20

MAX.0.300.250.200.168º

PowerAnalogMicroelectronics,Inc

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09/2008Rev1.1

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PAM2842

HighPowerLEDDriver

OutlineDimensions

QFN6X6-40

QFNUnit:millimeterPowerAnalogMicroelectronics,Inc

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09/2008Rev1.1

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