User's Guide SNVA191D–December2006–RevisedApril2013 AN-1536 LM3676 Evaluation Board 1 Introduction TheLM3676evaluationboardisaworkingdemonstrationofastepdownDC-DCconverter.This applicationnotecontainsinformationabouttheevaluationboard.Forfurtherinformationonbuckconverter topology,deviceelectricalcharacteristics,andcomponentselectionpleaserefertotheLM36762-MHz 600-mAStep-DownDC-DCConverterWithModeControl(SNVS426). 2 General Description TheLM3676convertshighinputvoltagestoloweroutputvoltageswithhighefficiencythroughaninductor basedswitchingtopology.TheLM3676hasamode-controlpinthatallowstheusertoselectcontinuous ForcedPWMmodeoverthecompleteloadrangeoranintelligentAuto,PFM-PWM,modethatchanges modesdependingontheload.SettingtheModepinlow(<0.4V)placestheLM3676inAutomodewere hystereticPFMextendsthebatterylifethroughreductionofthequiescentcurrentto16µA(typ.)during lightloadsandsystemstandby.WhentheModepinishigh(>1.0V)thepartofferssuperiorefficiency underhighloadconditions(>100mA)andthelowestoutputnoiseperformanceduringForcedPWM.The LM3676isavailableinbothfixedandadjustableoutputvoltageoptionsrangingfrom1.0Vto3.3Vina8- leadnon-pullbackWSONpackage(3mm×3mm). 3 Operating Conditions • V range:2.9V≤ V ≤ 5.5V IN IN • Recommendedloadcurrent:0mA≤ I ≤ 600mA OUT • Ambienttemperature(T )range:-30Cto+85C A • Junctiontemperature(T)range:-30Cto+125C J 4 Typical Application VIN L1: 2.2 PH 2.9V to 5.5V VIN SW VOUT 8 2 CIN LM3676 COUT 10 PF 4.7 PF PGND FB 1 4 NC SGND 6 7 EN 5 3 MODE Figure1.TypicalApplicationCircuit:FixedVoltage Alltrademarksarethepropertyoftheirrespectiveowners. SNVA191D–December2006–RevisedApril2013 AN-1536LM3676EvaluationBoard 1 SubmitDocumentationFeedback Copyright©2006–2013,TexasInstrumentsIncorporated

OutputVoltageSelectionforLM3676SD-ADJ www.ti.com VIN L1: 2.2 PH 2.9V to 5.5V VIN 8 2 SW VOUT 4.C7I NPF PGND LMA3D6J76-4 FB C1 R1 1C0O PUFT 1 SGND 7 C2 NC 6 R2 EN 3 MODE 5 Figure2.TypicalApplicationCircuit:AdjustableVoltage 5 Output Voltage Selection for LM3676SD-ADJ Theoutputvoltageoftheadjustablepartscanbeprogrammedthroughtheresistornetworkconnected fromV toFBtoGND.TheresistorfromFBtoGND(R )shouldbe200kΩ tokeepthecurrentdrawn OUT 2 throughthisnetworksmall,butlargeenoughthatitisnotsusceptibletonoise.IfR is200kΩ,andgiven 2 theV is0.5V,thenthecurrentthroughtheresistorfeedbacknetworkwillbe2.5µA.Theoutputvoltage FB formulais: VOUT = VFB (R1 + 1) R2 (1) where: V =outputvoltage(V) OUT V =feedbackvoltage(0.5Vtypical) FB R =feedbackresistorfromV toFB(Ω ) 1 OUT R =feedbackresistorfromFBtoGND(Ω) 2 Forthefixedoutputvoltageparts,thefeedbackresistorsareinternal.ThebypasscapacitorsC andC in 1 2 parallelwiththefeedbackresistorsarechosenforstableoperation.FollowingaretheformulasforC and 1 C : 2 1 C1 = 2 x S x R1 x 45 kHz (2) 1 C2= 2 x S x R2 x 45 kHz (3) Table1. LM3676-ADJConfigurationsforVariousV (CircuitofFigure2) out V (V) R(kΩ) R(kΩ) C(pF) C(pF) L(µH) C (µF) C (µF) OUT 1 2 1 2 IN OUT 1.0 200 200 18 None 2.2 4.7 10 1.1 191 158 18 None 2.2 4.7 10 1.2 280 200 12 None 2.2 4.7 10 1.5 357 178 10 None 2.2 4.7 10 1.6 442 200 8.2 None 2.2 4.7 10 1.7 432 178 8.2 None 2.2 4.7 10 1.8 464 178 8.2 None 2.2 4.7 10 1.875 523 191 6.8 None 2.2 4.7 10 2.5 402 100 8.2 None 2.2 4.7 10 2.8 464 100 8.2 33 2.2 4.7 10 3.3 562 100 6.8 33 2.2 4.7 10 2 AN-1536LM3676EvaluationBoard SNVA191D–December2006–RevisedApril2013 SubmitDocumentationFeedback Copyright©2006–2013,TexasInstrumentsIncorporated

www.ti.com PoweringtheLM3676forBenchMeasurement 6 Powering the LM3676 for Bench Measurement WhenpoweringtheLM3676withabenchpowersupply,itisrecommendedtoplacea100µFtantalum capacitoracrosstheVINandGNDsupplyterminalsofthebenchpowersupply.Thiscapacitorwillreduce theinputspikecausedbythepowersupplyandlongpowercables.Thecombinationofthepowersupply andinductancewithinthepowercablesproducealargevoltagespikethatmaydamagethedevice.In addition,considerationmustgiventotheenablepinofthedevice.Theenableshouldneverbetakenhigh, untilminimumspecifiedoperatingvoltageof2.7Visreached.Theenablepinshouldalsoneverexceed theinputvoltage. 7 Connection Diagram and Package Mark Information PGND 1 8 VIN SW 2 7 SGND MODE 3 6 NC FB 4 5 EN Figure3. WSON,TopView 8 Pin Descriptions (8-lead Non-Pullback WSON Package) Pin# Name Description 1 PGND Powersupplyinput. 2 SW SwitchingnodeconnectiontotheinternalPFETswitchandNFETsynchronous rectifier. 3 MODE ModeControlPin: >1.0VselectscontinousPWMmode; <0.4VselectsAuto(PFM-PWM)mode.Donotleavethispinfloating. 4 FB Feedbackanaloginput.Connectdirectlytotheoutputfiltercapacitorforfixedvoltage versions.Foradjustableversionexternalresistordividersarerequired(Figure2).The internalresistordividersaredisabledfortheadjustableversion. 5 EN Enablepin.Thedeviceisinshutdownmodewhenvoltagetothispinis<0.4Vand enabledwhen>1.0V.Donotleavethispinfloating. 6 NC NotConnected.KeepPinfloating 7 SGND SignalGroundPin. 8 VIN PowerSupplyinput.Connecttotheinputfiltercapacitor(Figure1). SNVA191D–December2006–RevisedApril2013 AN-1536LM3676EvaluationBoard 3 SubmitDocumentationFeedback Copyright©2006–2013,TexasInstrumentsIncorporated

EvaluationBoardLayout www.ti.com 9 Evaluation Board Layout Figure4.TopLayer(WSON-8pin) Figure5. BottomLayer(WSON-8pin) 4 AN-1536LM3676EvaluationBoard SNVA191D–December2006–RevisedApril2013 SubmitDocumentationFeedback Copyright©2006–2013,TexasInstrumentsIncorporated

www.ti.com BillofMaterialsforCommonConfigurations 10 Bill of Materials for Common Configurations Part Manufacture Manufacture# Description LM3676-3.3VAdjustable TexasInstruments C1(inputC) TDK C2012XR0J475K 4.7µF,6.3V,0805,10% C2(outputC) TDK C2012X5R0J106K 10µF,6.3V,0805,10% L1(inductor) Coilcraft DO3314-222MX 2.2µHinductor,1.6Asat R1(V toV ) Vishay CRCW06035623F 562kΩ,0603,1% OUT FB R2(V toGND) Vishay CRCW06031003F 100kΩ,0603,1% FB C3(V toV ) Vishay VJ0603A6R8KXAA 6.8pF,0603,10% OUT FB C4(V toGND) Vishay VJ0603A330KXAA 33pF,0603,10% FB V bananajack-red JohnsonComponents 108-0902-001 connector,insulatedbananajack(red) IN V bananajack-yellow JohnsonComponents 108-0907-001 connector,insulatedbananajack(yellow) OUT GNDbananajack-black JohnsonComponents 108-0903-001 connector,insulatedbananajack(black) PostforEN Turrent 1573-2 Uprightpostfromevalboard PostforV Turrent 1502-2 Uprightpostfromevalboard IN PostforV Turrent 1502-2 Uprightpostfromevalboard OUT PostforGND Turrent 1502-2 Uprightpostfromevalboard SNVA191D–December2006–RevisedApril2013 AN-1536LM3676EvaluationBoard 5 SubmitDocumentationFeedback Copyright©2006–2013,TexasInstrumentsIncorporated

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