User's Guide SNVA137A–December2005–RevisedApril2013 AN-1423 LM5010A Evaluation Board 1 Introduction TheLM5010AEVALevaluationboardprovidesthedesignengineerwithafullyfunctionalbuckregulator, employingtheconstanton-time(COT)operatingprinciple.Thisevaluationboardprovidesa5Voutput overaninputrangeof6V-75V.Thecircuitdeliversloadcurrentsto1A,withcurrentlimitsetat≊1.3A. TheboardispopulatedwithallexternalcomponentsexceptR6andC9-C11.Thesecomponentsprovide optionsforreducingoutputrippleasdescribedlaterinthisdocument. Theboard’sspecificationare: • InputVoltage:6Vto75V • OutputVoltage:5V • Maximumloadcurrent:1.0A • Minimumloadcurrent:0A • CurrentLimit:1.3A • MeasuredEfficiency:94.75%(V =6V,I =200mA) IN OUT • NominalSwitchingFrequency:200kHz • Size:2.25in.x0.88in.x0.47in R3C11 S/N C2 6 9 R2 R5 R C C10 C8 D1 C5 C1 C4 R4 J3 2 T U N O I 1 U1 C6 R C3 1 D T N U G LM5010A BUC K O J1 EVALUATION L1 NATIONAL BOARD C7 D N SEMICONDUCTOR C2005 P/N 55101 2686-001 REV AG Figure1.EvaluationBoard-TopSide 2 Theory of Operation TheevaluationboardschematicinFigure3containsasimplifiedblockdiagramoftheLM5010A, LM5010A-Q1High-Voltage1-AStep-DownSwitchingRegulatorDataSheet(SNVS376).Whenthecircuit isinregulation,thebuckswitchisoneachcycleforatimedeterminedbyR1andV accordingto IN Equation1: 1.18 x 10-10 x (R1+ 1.4k) tON = + 67 ns (VIN - 1.4V) (1) Alltrademarksarethepropertyoftheirrespectiveowners. SNVA137A–December2005–RevisedApril2013 AN-1423LM5010AEvaluationBoard 1 SubmitDocumentationFeedback Copyright©2005–2013,TexasInstrumentsIncorporated

BoardLayoutandProbing www.ti.com Theon-timeofthisevaluationboardrangesfrom≊5000nsatV =6V,to ≊380nsatV =75V.Theon- IN IN timevariesinverselywithV tomaintainanearlyconstantswitchingfrequency.Attheendofeachon- IN timetheMinimumOff-Timerensuresthebuckswitchisoffforatleast260ns.Innormaloperation,theoff- timeismuchlonger.Duringtheoff-time,theoutputcapacitor(C7)isdischargedbytheloadcurrent.When theoutputvoltagefallssufficientlythatthevoltageatFBisbelow2.5V,theregulationcomparatorinitiates anewon-timeperiod.Forstable,fixedfrequencyoperation,≊25mVofrippleisrequiredatFBtoswitch theregulationcomparator.Foramoredetailedblockdiagramandacompletedescriptionofthevarious functionalblocks,seetheLM5010A,LM5010A-Q1High-Voltage1-AStep-DownSwitchingRegulatorData Sheet(SNVS376). 3 Board Layout and Probing Figure1showstheplacementofthecircuitcomponents.Thefollowingshouldbekeptinmindwhenthe boardispowered: • Whenoperatingathighinputvoltageandhighloadcurrent,forcedairflowisnecessary. • TheLM5010A,andthediodeD1willbehottothetouchwhenoperatingathighinputvoltageandhigh loadcurrent. • UseCAUTIONwhenprobingthecircuitathighinputvoltagestopreventinjury,aswellaspossible damagetothecircuit. • Atmaximumloadcurrent(1A),thewiresizeandlengthusedtoconnecttheloadbecomesimportant. Ensurethereisnotasignificantdropinthewiresbetweenthisevaluationboardandtheload. 4 Board Connection/Start-up TheinputconnectionsaremadetotheJ1connector.TheloadisnormallyconnectedtotheOUT1and GNDterminalsoftheJ3connector.Ensurethewiresareadequatelysizedfortheintendedloadcurrent. Beforestart-upavoltmetershouldbeconnectedtotheinputterminals,andtotheoutputterminals.The loadcurrentshouldbemonitoredwithanammeteroracurrentprobe.Itisrecommendedthattheinput voltagebeincreasedgraduallyto6V,atwhichtimetheoutputvoltageshouldbe5V.Iftheoutputvoltage iscorrectwith6VatV ,thenincreasetheinputvoltageasdesiredandproceedwithevaluatingthecircuit. IN 5 Reducing Output Ripple TheLM5010Arequiresaminimumof25mVp-prippleattheFBpin,inphasewiththeswitchingwaveform attheSWpin,forproperoperation.Inthebasicapplicationcircuitshowninthedevice-specificdatasheet, C8isnotincluded.TherequiredrippleatFBisderivedfromtherippleatV ,whichisgeneratedbythe OUT1 inductor’sripplecurrentpassingthroughR4andtheESRofcapacitorC7.SincetheripplevoltageatV OUT1 isattenuatedbytheR2/R3feedbackdivider,aminimumof50mVp-pisrequiredatV .Ifthisripple OUT1 levelisacceptablefortheintendedapplication,C8canberemovedfromthisevaluationboard,andR4 increasedto1.5Ω.Inthatcase,theminimumrippleamplitude(≊55mVp-p)occursatminimumVin(6V), andincreasesto≊340mVp-patVin=75V,asshowninFigure6. Ifalowrippleoutputisdesired,threealternativesaredescribedinSection5.1,Section5.2,and Section5.3. 5.1 Option A: Ripple Reduction ThisEVBissuppliedwithC8installed,andR4=0.68Ω,providingarelativelylowrippleoutputatV OUT1 sinceC8couplestheoutputrippledirectlytoFBwithoutattenuation.TherippleamplitudeatV ranges OUT1 from30mVp-pto170mVp-p(seeFigure6)asVinisvariedoveritsrange.TheminimumvalueforC8is calculatedfrom: t ON(max) C8 = (R2//R3) (2) where,t isthemaximumon-timeatminimumVin,andR2//R3istheequivalentparallelvalueofR2 ON(max) andR3.Forthisevaluationboard,t isapproximately5000ns,andR2//R3=500Ω,resultingina ON(max) minimumvalueof0.01µFforC8. 2 AN-1423LM5010AEvaluationBoard SNVA137A–December2005–RevisedApril2013 SubmitDocumentationFeedback Copyright©2005–2013,TexasInstrumentsIncorporated

www.ti.com ReducingOutputRipple 5.2 Option B: Ripple Reduction AddR6,C9,C10,replaceR4withzeroohms,andleaveC8andC11positionsopen.SincetheSWpin switchesfrom-1VtoV ,andtherightendofC9isavirtualground,R6andC9arechosentogeneratea IN 30-40mVp-ptrianglewaveattheirjunction.ThattrianglewaveiscoupledtotheFBpinthroughC10.To calculatethevaluesforR6,C9,andC10,usethefollowingprocedure,usingtheminimuminputvoltage forVin: CalculatethevoltageV : A V =V -(V x(1-(V /Vin))) (3) A OUT SW OUT where,V istheabsolutevalueofthevoltageattheSWpinduringtheoff-time(typically1V),andVinis SW theminimuminputvoltage.Forthiscircuit,V calculatesto4.83V.ThisistheDCvoltageattheR6/C9 A junction,andisusedinEquation4. CalculatetheR6•C9product: (Vin - V ) x t R6(cid:135)C9 = A ON ’V (4) where,t istheon-timeatminimumVin(≊5 µs),and ΔVisthedesiredrippleamplitudeattheR6/C9 ON junction,30mVforthisexample. (6V – 4.83V) x 5 R6(cid:135)C9 = Ps = 1.95 x 10-4 0.03V (5) R6andC9arethenchosenfromstandardvaluecomponentstosatisfytheaboveproduct.Forexample, C9canbe1000pF,requiringR6tobe195kΩ.C10ischosentobe0.01µF,largecomparedtoC9.R2 andR3areincreasedto5kΩ eachtoreducetheloadingonthesignalprovidedthroughC10.The resultingcircuitis: LM5010A BST 3 0.022PF C6 L1 100(cid:3)PH SW 5V 2 V D1 R6 C9 OUT1 ISEN 195k 1000 pF R2 R4 C10 4 0.01PF 5k 0 FB 9 C7 R3 22 PF 6 RTN 5 SGND 5k Gnd Figure2.LowRippleOutputUsingR6,C9,C10 TheresultingrippleatV rangesfrom5mVp-patVin=6V,to18mVp-patVin=75V,andvaries OUT1 slightlywithloadcurrent,seeFigure6.Thesevaluesarevalidonlyforcontinuousconductionmode(load currentisbetween120mAand1.3A).Iftheloadcurrentisreducedbelow120mAsuchthatthecircuit operatesindiscontinuousconductionmodetheV ripplerangesfrom≊40mVp-pto≊100mVp-p.Ifthe OUT1 circuitisoperatedincurrentlimitmodetheripplerangesfrom≊100mVp-pto ≊300mVp-p. 5.3 Option C: Ripple Reduction ConnecttheloadtoV (leaveR4in).Therippleatthisoutputvariesfrom≊3mVp-pto ≊7.5mVp-pover OUT2 theinputvoltagerange,seeFigure6.However,theloadregulationisnotasgoodatV asatV due OUT2 OUT1 tothepresenceofR4.Thisalternativemaybepreferredforapplicationswheretheloadcurrentis relativelyconstant. SNVA137A–December2005–RevisedApril2013 AN-1423LM5010AEvaluationBoard 3 SubmitDocumentationFeedback Copyright©2005–2013,TexasInstrumentsIncorporated

IncreasingtheCurrentLimit www.ti.com 6 Increasing the Current Limit Theevaluationboardcurrentlimitactivatesataloadcurrentof≊1.3A.Ifitisdesiredtoincreasethe currentlimitforaparticularapplication,R5mustbeaddedtotheboard.Todeterminetheappropriate valueforthisresistor,seetheLM5010A,LM5010A-Q1High-Voltage1-AStep-DownSwitchingRegulator DataSheet(SNVS376). 7 Minimum Load Current TheLM5010Arequiresaminimumloadcurrentof≊500 µAtoensuretheboostcapacitor(C6)is rechargedsufficientlyduringeachoff-time.Inthisevaluationboard,theminimumloadcurrentisprovided bythefeedbackresistor(R2,R3),allowingtheboard’sminimumloadcurrentatV (orV )tobe OUT1 OUT2 specifiedatzero. 6V -7 5V VIN LM5010A Vin VCC 13 12 C4 C1 C2 C3 Minimum 0.47PF 2.2 PF 2.2 R1 On Off PF 200k 0.1 PF Timer Timer BST Gnd VIN 3 0.022PF C6 L1 100 PH RON/SD Logic SW 5V 11 2 V SS 2.5V D1 R6 C9 OUT1 0.022 CPF5 F1B0 Regulation 4ISEN R5 C10 0C.P0F81 1R.02k 0R.648 V 9 OUT2 Comparator SGND C7 C11 5 R3 22 PF 1.0k 6 RTN Gnd Figure3.EvaluationBoardSchematic Table1.BillofMaterials(BOM) Item Description Mfg.,PartNumber Package Value C1,2 CeramicCapacitor TDKC4532X7R2A225M 1812 2.2µF,100V C3 CeramicCapacitor TDKC2012X7R2A104M 0805 0.1µF,100V C4 CeramicCapacitor TDKC2012X7R1C474M 0805 0.47µF,16V C5,6 CeramicCapacitor TDKC2012X7R1C223M 0805 0.022µF,16V C7 CeramicCapacitor TDKC4532X7R1E226M 1812 22µF,25V C8 CeramicCapacitor TDKC2012X7R1C103M 0805 0.01µF,16V C9 Unpopulated C10 Unpopulated C11 Unpopulated D1 SchottkyDiode CentralSemiCMSH2-100 SMB 100V,2A L1 PowerInductor TDKSLF12575T-101M1R9,or 12.5mmx12.5mm 100µH,1.9A CooperBussmannDR125-101 R1 Resistor CRCW08052003F 0805 200kΩ R2,3 Resistor CRCW08051001F 0805 1.00kΩ R4 Resistor ERJ-6RQFR68V(Panasonic) 0805 0.68Ω R5 Unpopulated R6 Unpopulated U1 SwitchingRegulator TexasInstrumentsLM5010 HTSSOP-14 4 AN-1423LM5010AEvaluationBoard SNVA137A–December2005–RevisedApril2013 SubmitDocumentationFeedback Copyright©2005–2013,TexasInstrumentsIncorporated

www.ti.com MinimumLoadCurrent 100 VIN = 6V 90 )% ( Y 80 C N E IC 70 10V IF 20V F E 40V 60 75V 60V 50 050 200 400 600 800 1000 LOAD CURRENT (mA) Figure4.EfficiencyvsLoadCurrent 100 Load Current = 200 mA 90 Load Current = 1000 mA )% ( Y 80 C N E IC 70 IF F E 60 Load Current = 50 mA 50 0 6 20 40 60 75 VIN (V) Figure5.EfficiencyvsV IN 400 Load Current = 200 mA R6, C8-C11 Not Installed R4 = 1.5: )p 300 -p V m ( 1 T UO 200 V C8 = 0.01 PF, R4 = 0.68: @ E L P PIR 100 R6 = 195 k:, C9 = 1 nF, Ripple @ R4 = 0 C10 = 0.01 PF VOUT2 0 0 6 20 40 60 75 VIN (V) Figure6.VoltageRippleatV ,V OUT1 OUT2 SNVA137A–December2005–RevisedApril2013 AN-1423LM5010AEvaluationBoard 5 SubmitDocumentationFeedback Copyright©2005–2013,TexasInstrumentsIncorporated

PCBLayout www.ti.com 8 PCB Layout Figure7.BoardSilkscreen Figure8.BoardTopLayer Figure9.BoardBottomLayer(viewedfromtop) 6 AN-1423LM5010AEvaluationBoard SNVA137A–December2005–RevisedApril2013 SubmitDocumentationFeedback Copyright©2005–2013,TexasInstrumentsIncorporated

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