LM2700LDX-ADJ/NOPB

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LM2700 600kHz/1.25MHz, 2.5A, Step-up PWM DC/DC Converter

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LM2700 600kHz/1.25MHz, 2.5A, Step-up PWM DC/DC Converter (Rev. C)

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Manufacturer or author: Texas Instruments, Incorporated [SNVS152,C]
PDF pages: 26

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www.ti.com SNVS152C –MAY 2001–REVISED MARCH 2013 LM2700600kHz/1.25MHz,2.5A,Step-upPWM DC/DCConverter Check forSamples: LM2700 1FEATURES DESCRIPTION The LM2700 is a step-upDC/DC converterwitha 2• 3.6A,0.08Ω,InternalSwitch 3.6A, 80m Ω internalswitch and pin selectable• OperatingInputVoltageRange of2.2Vto12V operatingfrequency.With the abilityto produce

InputUndervoltageProtection 500mA at 8V from a singleLithiumIon battery,the LM2700 isan idealpartforbiasingLCD displays.The• AdjustableOutput Voltageup to17.5V LM2700 can be operatedatswitchingfrequenciesof• 600kHz/1.25MHz Pin SelectableFrequency 600kHz and 1.25MHz allowingforeasy filteringandOperation low noise.An externalcompensationpin givesthe
Over Temperature Protection user flexibilityin settingfrequencycompensation, which makes possiblethe use of small,low ESR• Small 14-Lead TSSOP or WSON Package ceramic capacitorsat the output.The LM2700 featurescontinuousswitchingat lightloads andAPPLICATIONS operateswitha switchingquiescentcurrentof2.0mA
LCD Bias Supplies at 600kHz and 3.0mA at 1.25MHz. The LM2700 is availableina low profile14-leadTSSOP package or• Handheld Devices a 14-leadWSON package.• PortableApplications
GSM/CDMA Phones
DigitalCameras TypicalApplicationCircuit Figure1. 600 kHz Operation Pleasebe aware thatan importantnoticeconcerningavailability,standardwarranty,and use incriticalapplicationsof Texas Instrumentssemiconductorproductsand disclaimerstheretoappearsattheend ofthisdatasheet. 2Alltrademarksarethepropertyoftheirrespectiveowners. PRODUCTION DATA informationiscurrentas ofpublicationdate. Copyright© 2001–2013,Texas InstrumentsIncorporatedProductsconform to specificationsper the terms of the Texas Instrumentsstandardwarranty.Productionprocessingdoes not necessarilyincludetestingofallparameters.

SNVS152C –MAY 2001–REVISED MARCH 2013 www.ti.com Connection Diagram Figure2. Top View 14-Lead TSSOP or WSON PIN DESCRIPTION Pin Name Function 1 VC Compensationnetworkconnection.Connectedtotheoutputofthevoltageerroramplifier. 2 FB Outputvoltagefeedbackinput. 3 SHDN Shutdown controlinput,activelow. 4 AGND Analogground. 5 PGND Power ground.PGND pinsmust be connectedtogetherdirectlyatthepart. 6 PGND Power ground.PGND pinsmust be connectedtogetherdirectlyatthepart. 7 PGND Power ground.PGND pinsmust be connectedtogetherdirectlyatthepart. 8 SW Power switchinput.Switchconnectedbetween SW pinsand PGND pins. 9 SW Power switchinput.Switchconnectedbetween SW pinsand PGND pins. 10 SW Power switchinput.Switchconnectedbetween SW pinsand PGND pins. 11 NC Pinnotconnectedinternally. 12 VIN Analogpower input. 13 FSLCT Switchingfrequencyselectinput.VIN = 1.25MHz.Ground = 600kHz. 14 NC Connecttoground.

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www.ti.com SNVS152C –MAY 2001–REVISED MARCH 2013 Block Diagram DetailedDescription The LM2700 utilizesa PWM controlscheme toregulatetheoutputvoltageoverallloadconditions.The operation can bestbe understoodreferringto the blockdiagram and Figure17 of the Operationsection.At the startof each cycle,theoscillatorsetsthedriverlogicand turnson theNMOS power deviceconductingcurrentthrough the inductor,cycle1 of Figure17(a).Duringthiscycle,the voltageat the VC pincontrolsthe peak inductor current.The VC voltagewillincreasewithlargerloadsand decreasewithsmaller.Thisvoltageiscompared with the summation of the SW voltageand the ramp compensation.The ramp compensationis used in PWM architecturestoeliminatethesub-harmonicoscillationsthatoccurduringdutycyclesgreaterthan50%. Once the summation oftheramp compensationand switchvoltageequalstheVC voltage,thePWM comparatorresetsthe driverlogicturningofftheNMOS power device.The inductorcurrentthenflowsthroughtheschottkydiodetothe loadand outputcapacitor,cycle2 ofFigure17(b).The NMOS power deviceisthensetby theoscillatoratthe end oftheperiodand currentflowsthroughtheinductoronce again. The LM2700 has dedicatedprotectioncircuitryrunningduringnormaloperationtoprotecttheIC.The Thermal Shutdown circuitryturnsofftheNMOS power devicewhen thedietemperaturereachesexcessivelevels.The UVP comparatorprotectsthe NMOS power deviceduringsupplypower startupand shutdown to prevent operationatvoltageslessthantheminimum inputvoltage.The OVP comparatorisused topreventtheoutput voltagefromrisingatno loadsallowingfullPWM operationoverallloadconditions.The LM2700 alsofeaturesa shutdownmode decreasingthesupplycurrentto5µA. These deviceshave limitedbuilt-inESD protection.The leadsshouldbe shortedtogetherorthedeviceplacedinconductivefoam duringstorageorhandlingtopreventelectrostaticdamage totheMOS gates. Copyright© 2001–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 3 ProductFolderLinks:LM2700

SNVS152C –MAY 2001–REVISED MARCH 2013 www.ti.com AbsoluteMaximum Ratings(1)(2) VIN 12V SW Voltage 18V FB Voltage 7V VC Voltage 0.965V≤ VC ≤ 1.565V SHDN Voltage(3) 7V FSLCT (3) 12V Maximum JunctionTemperature 150°C Power Dissipation(4) InternallyLimited Lead Temperature 300°C Vapor Phase (60sec.) 215°C Infrared(15sec.) 220°C ESD Susceptibility(5) Human Body Model 2kV Machine Model 200V (1) Absolutemaximum ratingsarelimitsbeyond whichdamage tothedevicemay occur.OperatingRatingsareconditionsforwhichthe deviceisintendedtobe functional,butdeviceparameterspecificationsmay notbe ensured.Forensuredspecificationsand test conditions,see theElectricalCharacteristics. (2) IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheTexas InstrumentsSalesOffice/Distributorsforavailabilityand specifications. (3) Thisvoltageshouldneverexceed VIN. (4) The maximum allowablepower dissipationisa functionofthemaximum junctiontemperature,TJ(MAX),thejunction-to-ambientthermal resistance,θJA,and theambienttemperature,TA.See theElectricalCharacteristicstableforthethermalresistance.The maximum allowablepower dissipationatany ambienttemperatureiscalculatedusing:PD (MAX) = (TJ(MAX) − TA)/θJA.Exceedingthemaximum allowablepower dissipationwillcause excessivedietemperature,and theregulatorwillgo intothermalshutdown. (5) The human body model isa 100 pF capacitordischargedthrougha 1.5kΩ resistorintoeach pin.The machine model isa 200pF capacitordischargeddirectlyintoeach pin. OperatingConditions OperatingJunctionTemperatureRange (1) −40°C to+125°C StorageTemperature −65°C to+150°C SupplyVoltage 2.2Vto12V SW Voltage 17.5V (1) Alllimitsspecifiedatroom temperature(standardtypeface)and attemperatureextremes(boldtypeface).Allroom temperaturelimitsare 100% testedorensuredthroughstatisticalanalysis.Alllimitsattemperatureextremesareensuredviacorrelationusingstandard StatisticalQualityControl(SQC) methods.Alllimitsareused tocalculateAverageOutgoingQualityLevel(AOQL).

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www.ti.com SNVS152C –MAY 2001–REVISED MARCH 2013 ElectricalCharacteristics SpecificationsinstandardtypefaceareforTJ = 25°C and thosewithboldfacetypeapplyoverthefullOperating Temperature Range (TJ = −40°C to+125°C) Unlessotherwisespecified.VIN =2.2V and IL = 0A,unlessotherwisespecified. Min Typ MaxSymbol Parameter Conditions Units(1) (2) (1) IQ QuiescentCurrent FB = 2.2V(NotSwitching) 1.2 2 mAFSLCT = 0V FB = 2.2V(NotSwitching) 1.3 2 mAFSLCT = VIN VSHDN = 0V 5 20 µA VFB Feedback Voltage 1.2285 1.26 1.2915 V ICL (3) SwitchCurrentLimit VIN = 2.7V(4) 2.55 3.6 4.3 A %V FB /ΔVIN Feedback VoltageLine 2.2V≤ VIN ≤ 12.0V 0.02 0.07 %/V Regulation IB FB PinBiasCurrent 0.5 40 nA(5) VIN InputVoltageRange 2.2 12 V gm ErrorAmp Transconductance ΔI= 5µA 40 155 290 µmho AV ErrorAmp VoltageGain 135 V/V D MAX Maximum DutyCycle FSLCT = Ground 78 85 % D MIN Minimum DutyCycle FSLCT = Ground 15 FSLCT = VIN 30 fS SwitchingFrequency FSLCT = Ground 480 600 720 kHz FSLCT = VIN 1 1.25 1.5 MHz ISHDN Shutdown PinCurrent VSHDN = VIN 0.008 1 µA VSHDN = 0V −0.5 −1 IL SwitchLeakage Current VSW = 18V 0.02 20 µA R DSON SwitchR DSON (6) VIN = 2.7V,ISW = 2A 80 150 m Ω ThSHDN SHDN Threshold OutputHigh 0.9 0.6 V OutputLow 0.6 0.3 V UVP On Threshold 1.95 2.05 2.2 V OffThreshold 1.85 1.95 2.1 V θJA ThermalResistance(7) TSSOP, package only 150 °C/W WSON, package only 45 (1) Alllimitsspecifiedatroom temperature(standardtypeface)and attemperatureextremes(boldtypeface).Allroom temperaturelimitsare 100% testedorensuredthroughstatisticalanalysis.Alllimitsattemperatureextremesareensuredviacorrelationusingstandard StatisticalQualityControl(SQC) methods.Alllimitsareused tocalculateAverageOutgoingQualityLevel(AOQL). (2) Typicalnumbers areat25°C and representthemost likelynorm. (3) Dutycycleaffectscurrentlimitdue toramp generator. (4) Currentlimitat0% dutycycle.See TypicalPerformanceCharacteristicssectionforSwitchCurrentLimitvs.VIN (5) BiascurrentflowsintoFB pin. (6) Does notincludethebond wires.Measured directlyatthedie. (7) RefertoTexas Instrument's packagingwebsiteformore detailedthermalinformationand mountingtechniquesfortheWSON and TSSOP packages. Copyright© 2001–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 5 ProductFolderLinks:LM2700

SNVS152C –MAY 2001–REVISED MARCH 2013 www.ti.com TypicalPerformance Characteristics Efficiencyvs.Load Current Efficiencyvs.Load Current (VOUT = 8V,fS = 600 kHz) (VOUT = 8V,fS = 1.25MHz) Figure3. Figure4. Efficiencyvs.Load Current Efficiencyvs.Load Current (VOUT = 5V,fS = 600 kHz) (VOUT = 12V,fS = 600 kHz) Figure5. Figure6. Switch CurrentLimitvs.Temperature Switch CurrentLimitvs.VIN Figure7. Figure8.

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www.ti.com SNVS152C –MAY 2001–REVISED MARCH 2013 TypicalPerformance Characteristics(continued) R DSON vs.VIN IQ vs.VIN (ISW = 2A) (600kHz,not switching) Figure9. Figure10. IQ vs.VIN IQ vs.VIN (600kHz,switching) (1.25MHz, not switching) Figure11. Figure12. IQ vs.VIN IQ vs.VIN (1.25MHz, switching) (Inshutdown) Figure13. Figure14. Copyright© 2001–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 7 ProductFolderLinks:LM2700

SNVS152C –MAY 2001–REVISED MARCH 2013 www.ti.com TypicalPerformance Characteristics(continued) Frequency vs.VIN Frequency vs.VIN (600kHz) (1.25MHz) Figure15. Figure16.

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:R FB1 = RFB2 x VOUT - 1.26 1.26 VOUT = VIN 1-D , D' = (1-D) = VIN VOUT LM2700 www.ti.com SNVS152C –MAY 2001–REVISED MARCH 2013 Operation Figure17. SimplifiedBoost ConverterDiagram (a)FirstCycle ofOperation(b)Second Cycle Of Operation CONTINUOUS CONDUCTION MODE The LM2700 isa current-mode,PWM boostregulator.A boostregulatorstepstheinputvoltageup toa higher outputvoltage.Incontinuousconductionmode (when theinductorcurrentneverreacheszeroatsteadystate), theboostregulatoroperatesintwo cycles. In the firstcycleof operation,shown inFigure17(a),the transistorisclosedand the diodeisreversebiased. Energyiscollectedintheinductorand theloadcurrentissuppliedby C OUT . The second cycleisshown inFigure17(b).Duringthiscycle,the transistorisopen and the diodeisforward biased.The energystoredintheinductoristransferredtotheloadand outputcapacitor. The ratioofthesetwo cyclesdeterminestheoutputvoltage.The outputvoltageisdefinedapproximatelyas: (1) where D isthedutycycleoftheswitch,D and D ′ willbe requiredfordesigncalculations. SETTING THE OUTPUT VOLTAGE The outputvoltageissetusingthe feedbackpinand a resistordividerconnectedto the outputas shown in Figure19. The feedbackpinvoltageis1.26V,so the ratioof the feedbackresistorssetsthe outputvoltage accordingtothefollowingequation: (2) Copyright© 2001–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 9 ProductFolderLinks:LM2700

2S(RC + RO )CC fPC = Hz1fZC = 2SR C C C LM2700 SNVS152C –MAY 2001–REVISED MARCH 2013 www.ti.com INTRODUCTION TO COMPENSATION Figure18. (a)Inductorcurrent.(b)Diode current. The LM2700 isa currentmode PWM boostconverter.The signalflowofthiscontrolscheme has two feedback loops,one thatsensesswitchcurrentand one thatsensesoutputvoltage. To keep a currentprogrammed controlconverterstableabove duty cyclesof 50%, the inductormust meet certaincriteria.The inductor,alongwithinputand outputvoltage,willdeterminetheslopeofthecurrentthrough theinductor(seeFigure18(a)).Iftheslopeoftheinductorcurrentistoogreat,thecircuitwillbe unstableabove dutycyclesof 50%. A 4.7µH inductorisrecommended formost 600 kHz applications,whilea 2.2µH inductor may be used formost 1.25MHz applications.Ifthedutycycleisapproachingthemaximum of85%, itmay be necessaryto increasethe inductanceby as much as 2X. See Inductorand Diode Selectionformore detailed inductorsizing. The LM2700 providesa compensationpin(VC )tocustomizethevoltageloopfeedback.Itisrecommended thata seriescombinationofR C and C C be used forthecompensationnetwork,as shown inFigure19.For any given application,thereexistsa uniquecombinationofR C and C C thatwilloptimizetheperformanceoftheLM2700 circuitin terms of itstransientresponse.The seriescombinationof R C and C C introducesa pole-zeropair accordingtothefollowingequations: (3) (4)

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'iL = (in Amps) VIND 2Lfs VINR DSON 0.144 fs L > ( ) D ( ) D D' +1 (in H) LM2700 www.ti.com SNVS152C –MAY 2001–REVISED MARCH 2013 where R O is the outputimpedance of the erroramplifier,approximately850kΩ. For most applications, performancecan be optimizedby choosingvalueswithintherange5kΩ ≤ R C ≤ 20kΩ (RC can be up to200kΩ if C C2 isused,see High OutputCapacitorESR Compensation)and 680pF ≤ C C ≤ 4.7nF.RefertotheApplication Informationsectionforrecommended valuesforspecificcircuitsand conditions.RefertotheCOMPENSATION sectionforotherdesignrequirement. COMPENSATION Thissectionwillpresenta generaldesignproceduretohelpinsurea stableand operationalcircuit.The designs inthisdatasheetare optimizedforparticularrequirements.Ifdifferentconversionsare required,some of the components may need to be changed to ensure stability.Below isa setof generalguidelinesindesigninga stablecircuitforcontinuousconductionoperation(loadsgreaterthanapproximately100mA), inmost allcases thiswillprovideforstabilityduringdiscontinuousoperationas well.The power components and theireffectswill be determinedfirst,thenthecompensationcomponents willbe chosen toproducestability. INDUCTOR AND DIODE SELECTION Althoughthe inductorsizesmentioned earlierare fineformost applications,a more exact value can be calculated.To ensure stabilityat duty cyclesabove 50%, the inductormust have some minimum value determinedby theminimum inputvoltageand themaximum outputvoltage.Thisequationis: (5) where fsistheswitchingfrequency,D isthedutycycle,and R DSON istheON resistanceoftheinternalswitch takenfrom thegraph "RDSON vs.VIN" intheTypicalPerformanceCharacteristicssection.Thisequationisonly good fordutycyclesgreaterthan50% (D>0.5),fordutycycleslessthan50% therecommended valuesmay be used.The correspondinginductorcurrentrippleas shown inFigure18(a)isgivenby: (6) The inductorripplecurrentisimportantfora few reasons.One reasonisbecause thepeak switchcurrentwillbe theaverageinductorcurrent(inputcurrentor ILOAD /D')plusΔiL.As a sidenote,discontinuousoperationoccurs when the inductorcurrentfallsto zero duringa switchingcycle,or ΔiL isgreaterthan the average inductor current.Therefore,continuousconductionmode occurswhen ΔiL islessthantheaverageinductorcurrent.Care must be takentomake surethattheswitchwillnotreachitscurrentlimitduringnormaloperation.The inductor must alsobe sizedaccordingly.Itshouldhave a saturationcurrentratinghigherthanthepeak inductorcurrent expected.The outputvoltagerippleisalsoaffectedby thetotalripplecurrent. The outputdiodefora boostregulatormust be chosen correctlydependingon theoutputvoltageand theoutput current.The typicalcurrentwaveform forthediodeincontinuousconductionmode isshown inFigure18(b).The diodemust be ratedfora reversevoltageequaltoorgreaterthantheoutputvoltageused.The averagecurrent ratingmust be greaterthan the maximum loadcurrentexpected,and the peak currentratingmust be greater than the peak inductorcurrent.Duringshortcircuittesting,or ifshortcircuitconditionsare possiblein the application,the diode currentratingmust exceed the switchcurrentlimit.Using Schottkydiodeswithlower forwardvoltagedropwilldecreasepower dissipationand increaseefficiency. DC GAIN AND OPEN-LOOP GAIN Sincethecontrolstageoftheconverterformsa completefeedbackloopwiththepower components,itformsa closed-loopsystem thatmust be stabilizedtoavoidpositivefeedbackand instability.A valueforopen-loopDC gain willbe required,from which you can calculate,or place,polesand zeros to determinethe crossover frequencyand the phase margin.A highphase margin (greaterthan 45°) isdesiredforthe beststabilityand transientresponse.For thepurposeofstabilizingtheLM2700, choosinga crossoverpointwellbelow where the righthalfplanezeroislocatedwillensuresufficientphase margin.A discussionoftherighthalfplanezeroand checkingthecrossoverusingtheDC gainwillfollow. Copyright© 2001–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 11 ProductFolderLinks:LM2700

fZC = 1 2SC C R C (in Hz) fPC = 1 2S(RC + RO )CC (in Hz) (in Hz)RHPzero = VOUT (D')2 2S,LOAD L fZ1 = 1 2SR ESR C OUT (in Hz) fP1 = 1 2S(RESR + RL)COUT (in Hz) LM2700 SNVS152C –MAY 2001–REVISED MARCH 2013 www.ti.com INPUT AND OUTPUT CAPACITOR SELECTION The switchingactionof a boost regulatorcauses a triangularvoltagewaveform at the input.A capacitoris requiredtoreducetheinputrippleand noiseforproperoperationoftheregulator.The sizeused isdependanton theapplicationand board layout.Iftheregulatorwillbe loadeduniformly,withverylittleloadchanges,and at lowercurrentoutputs,theinputcapacitorsizecan oftenbe reduced.The sizecan alsobe reducediftheinputof theregulatorisveryclosetothesourceoutput.The sizewillgenerallyneed tobe largerforapplicationswhere theregulatorissupplyingnearlythemaximum ratedoutputoriflargeloadstepsareexpected.A minimum value of 10µF shouldbe used forthe lessstressfulcondtionswhilea 33µF or 47µF capacitormay be requiredfor higherpower and dynamic loads.Largervaluesand/orlowerESR may be needed iftheapplicationrequiresvery lowrippleon theinputsourcevoltage. The choiceofoutputcapacitorsisalsosomewhat arbitraryand depends on thedesignrequirementsforoutput voltageripple.Itisrecommended thatlowESR (EquivalentSeriesResistance,denotedR ESR )capacitorsbe used such as ceramic,polymerelectrolytic,orlow ESR tantalum.HigherESR capacitorsmay be used butwillrequire more compensationwhich willbe explainedlateron in the section.The ESR is also importantbecause it determinesthepeak topeak outputvoltagerippleaccordingtotheapproximateequation: ΔVOUT ≊ 2ΔiLR ESR (inVolts) (7) A minimum valueof10µF isrecommended and may be increasedtoa largervalue.Afterchoosingtheoutput capacitoryou can determinea pole-zeropairintroducedintothecontrolloopby thefollowingequations: (8) (9) Where R L istheminimum loadresistancecorrespondingtothemaximum loadcurrent.The zerocreatedby the ESR oftheoutputcapacitorisgenerallyveryhighfrequencyiftheESR issmall.Iflow ESR capacitorsareused it can be neglected.If higher ESR capacitorsare used see the HIGH OUTPUT CAPACITOR ESR COMPENSATION section. RIGHT HALF PLANE ZERO A currentmode controlboostregulatorhas an inherentrighthalfplanezero(RHP zero).Thiszerohas theeffect ofa zerointhegainplot,causingan imposed +20dB/decade on therolloff,buthas theeffectofa poleinthe phase, subtractinganother90° in the phase plot.This can cause undesirableeffectsifthe controlloop is influencedby thiszero.To ensuretheRHP zerodoes notcause instabilityissues,thecontrolloopshouldbe designedtohave a bandwidthoflessthan½ thefrequencyoftheRHP zero.Thiszerooccursata frequencyof: (10) where ILOAD isthemaximum loadcurrent. SELECTING THE COMPENSATION COMPONENTS The firststepinselectingthecompensationcomponents R C and C C istoseta dominantlow frequencypolein the controlloop.Simply choose valuesforR C and C C withinthe ranges givenin the INTRODUCTION TO COMPENSATION sectiontosetthispoleinthearea of10Hz to500Hz. The frequencyofthepolecreatedis determinedby theequation: (11) where R O istheoutputimpedance oftheerroramplifier,approximately850kΩ.SinceR C isgenerallymuch less thanR O ,itdoes nothave much effecton theabove equationand can be neglecteduntila valueischosen toset thezerofZC .fZC iscreatedtocanceloutthepolecreatedby theoutputcapacitor,fP1.The outputcapacitorpole willshiftwithdifferentloadcurrentsas shown by theequation,so settingthezeroisnotexact.Determinethe range of fP1 over the expectedloadsand then set the zero fZC to a pointapproximatelyin the middle.The frequencyofthiszeroisdeterminedby: (12)

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m1 # VINR DSON L (in V/s) n = 1+ 2mc m1 (no unit) Leff = L (D')2 Zc (in rad/s)2fs nD'# ADC(DB) = 20log10 {[(ZcLeff)// RL]//RL} (in dB) R FB1 + RFB2 R FB2 ( ) gm R O D' R DSON fPC2 = 1 2SC C2 (RC //RO ) (in Hz) LM2700 www.ti.com SNVS152C –MAY 2001–REVISED MARCH 2013 Now R C can be chosen withtheselectedvalueforC C .Check tomake surethatthepolefPC isstillinthe10Hz to 500Hz range,change each valueslightlyifneeded toensurebothcomponent valuesare intherecommended range.Aftercheckingthedesignattheend ofthissection,thesevaluescan be changed a littlemore tooptimize performanceifdesired.Thisisbestdone inthelabon a bench,checkingtheloadstepresponsewithdifferent valuesuntiltheringingand overshooton theoutputvoltageattheedge oftheloadstepsisminimal.Thisshould produce a stable,high performancecircuit.For improved transientresponse,highervaluesof R C shouldbe chosen.Thiswillimprovetheoverallbandwidthwhichmakes theregulatorrespondmore quicklytotransients.If more detailisrequired,or the most optimalperformanceisdesired,referto a more in depth discussionof compensatingcurrentmode DC/DC switchingregulators. HIGH OUTPUT CAPACITOR ESR COMPENSATION When usingan outputcapacitorwitha highESR value,orjusttoimprovetheoverallphase marginofthecontrol loop,anotherpolemay be introducedtocancelthezerocreatedby theESR. Thisisaccomplishedby adding anothercapacitor,C C2 ,directlyfromthecompensationpinVC toground,inparallelwiththeseriescombinationof R C and C C .The poleshouldbe placedatthesame frequencyas fZ1,theESR zero.The equationforthispole follows: (13) To ensurethisequationisvalid,and thatC C2 can be used withoutnegativelyimpactingtheeffectsofR C and C C , fPC2 must be greaterthan10fZC . CHECKING THE DESIGN The finalstepistocheck thedesign.Thisistoensurea bandwidthof½ or lessofthefrequencyoftheRHP zero.Thisisdone by calculatingtheopen-loopDC gain,ADC .Afterthisvalueisknown, you can calculatethe crossovervisuallyby placinga −20dB/decadeslopeateach pole,and a +20dB/decadeslopeforeach zero.The pointatwhichthegainplotcrossesunitygain,or0dB, isthecrossoverfrequency.Ifthecrossoverfrequencyis lessthan½ theRHP zero,thephase marginshouldbe highenough forstability.The phase margincan alsobe improvedby addingC C2 as discussedearlierinthesection.The equationforADC isgivenbelow withadditional equationsrequiredforthecalculation: (14) (15) (16) (17) mc ≊ 0.072fs(inV/s) (18) (19) where R L is the minimum load resistance,VIN is the minimum inputvoltage,gm is the erroramplifier transconductancefound inthe ElectricalCharacteristicstable,and R DSON isthe valuechosen from the graph "RDSON vs.VIN "intheTypicalPerformanceCharacteristicssection. Copyright© 2001–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 13 ProductFolderLinks:LM2700

SNVS152C –MAY 2001–REVISED MARCH 2013 www.ti.com LAYOUT CONSIDERATIONS The LM2700 uses two separateground connections,PGND forthedriverand NMOS power deviceand AGND forthe sensitiveanalog controlcircuitry.The AGND and PGND pinsshouldbe tieddirectlytogetherat the package.The feedbackand compensationnetworksshouldbe connecteddirectlytoa dedicatedanalogground planeand thisground planemust connectto the AGND pin.Ifno analogground planeisavailablethen the ground connectionsofthefeedbackand compensationnetworksmust tiedirectlytotheAGND pin.Connecting thesenetworkstothePGND can injectnoiseintothesystemand effectperformance. The inputbypass capacitorC IN,as shown inFigure19,must be placedclosetotheIC.Thiswillreducecopper traceresistancewhicheffectsinputvoltagerippleoftheIC.For additionalinputvoltagefiltering,a 100nF bypass capacitorcan be placedinparallelwithC IN,closetotheVIN pin,toshuntany highfrequencynoisetoground. The outputcapacitor,C OUT ,shouldalsobe placedclosetotheIC.Any coppertraceconnectionsfortheC OUT capacitorcan increasetheseriesresistance,whichdirectlyeffectsoutputvoltageripple.The feedbacknetwork, resistorsR FB1 and R FB2 , shouldbe keptcloseto the FB pin,and away from the inductor,to minimizecopper traceconnectionsthatcan injectnoiseintothe system.Trace connectionsmade to the inductorand schottky diode shouldbe minimizedto reduce power dissipationand increaseoverallefficiency.For more detailon switchingpower supplylayoutconsiderationssee ApplicationNote AN-1149: LayoutGuidelinesforSwitching Power Supplies(literaturenumber SNVA021 ).

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www.ti.com SNVS152C –MAY 2001–REVISED MARCH 2013

APPLICATION INFORMATION

Figure19. 600 kHz operation,8V output Figure20. 1.25MHz operation,8V output Figure21. 600 kHz operation,5V output Copyright© 2001–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 15 ProductFolderLinks:LM2700

SNVS152C –MAY 2001–REVISED MARCH 2013 www.ti.com VIN = 3.3V,IOUT = 200mA ⇝ 700mA ⇝ 200mA CH1: IOUT 0.5A/divDC Coupled CH2: VOUT 500mV/divAC Coupled CH3: InductorCurrent1A/divDC Coupled 20µs/div Figure22. Load TransientforFigure21 Figure23. 600 kHz operation,12V output

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www.ti.com SNVS152C –MAY 2001–REVISED MARCH 2013 VIN = 3.3V,IOUT = 50mA ⇝ 350mA ⇝ 50mA CH1: IOUT 0.5A/divDC Coupled CH2: VOUT 500mV/divAC Coupled CH3: InductorCurrent1A/divDC Coupled 50µs/div Figure24. Load TransientforFigure23 Figure25. TripleOutput TFT Bias (600kHz operation) Copyright© 2001–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 17 ProductFolderLinks:LM2700

SNVS152C –MAY 2001–REVISED MARCH 2013 www.ti.com VIN = 3.3V,IOUT = 500mA CH1: VIN 2V/divDC Coupled CH2: VOUT 5V/divDC Coupled CH3: InductorCurrent500mA/divDC Coupled 1ms/div Figure26. StartUp Waveform forFigure25 VIN = 3.3V,IOUT = 50mA ⇝ 375mA ⇝ 50mA CH1: IOUT 0.2A/divDC Coupled CH2: VOUT 2V/divAC Coupled CH3: InductorCurrent1A/divDC Coupled 500µs/div Figure27. Load TransientforFigure25,8V Output

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www.ti.com SNVS152C –MAY 2001–REVISED MARCH 2013

REVISION HISTORY

www.ti.com 1-Nov-2013 Addendum-Page 1 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Qty Eco Plan (2) Lead/Ball Finish (6) MSL Peak Temp (3) Op Temp (°C) Device Marking (4/5) Samples LM2700LD-ADJ/NOPB ACTIVE WSON NHE 14 1000 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 S00001B LM2700LDX-ADJ/NOPB ACTIVE WSON NHE 14 4500 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 S00001B LM2700MT-ADJ NRND TSSOP PW 14 94 TBD Call TI Call TI -40 to 125 2700MT -ADJ LM2700MT-ADJ/NOPB ACTIVE TSSOP PW 14 94 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2700MT -ADJ LM2700MTX-ADJ/NOPB ACTIVE TSSOP PW 14 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2700MT -ADJ (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device.

www.ti.com 1-Nov-2013 Addendum-Page 2 (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

*All dimensions are nominal Device Package Type Package Drawing Pins SPQ Reel Diameter (mm) Reel Width W1 (mm) (mm) (mm) (mm) (mm) W (mm) Pin1 Quadrant PACKAGE MATERIALS INFORMATION www.ti.com 6-Nov-2015 Pack Materials-Page 1

*All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2700LD-ADJ/NOPB WSON NHE 14 1000 213.0 191.0 55.0 LM2700LDX-ADJ/NOPB WSON NHE 14 4500 367.0 367.0 35.0 LM2700MTX-ADJ/NOPB TSSOP PW 14 2500 367.0 367.0 35.0 PACKAGE MATERIALS INFORMATION www.ti.com 6-Nov-2015 Pack Materials-Page 2

www.ti.com LDA14A (REV A)

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