K04RLM12 TI1 | Alldatasheet

Document overview

  • Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
  • PDF pages: 23

Technical content

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 LM12CL80WOperationalAmplifier Check forSamples: K04RLM12 ,LM12CL The turn-oncharacteristicsare controlledby keeping1FEATURES theoutputopen-circuiteduntilthetotalsupplyvoltage 2• InputProtection reaches14V. The outputisalsoopened as thecase

  • ControlledTurn On temperatureexceeds 150°C or as thesupplyvoltage approachestheBV CEO oftheoutputtransistors.The• Thermal Limiting IC withstandsovervoltagesto80V.• OvervoltageShutdown Thismonolithicop amp iscompensated forunity-gain• Output-CurrentLimiting feedback,witha small-signalbandwidthof 700 kHz.• Dynamic Safe-AreaProtection Slew rateis9V/μs,even as a follower.Distortionand capacitive-loadstabilityrivalthatofthebestdesigns DESCRIPTION usingcomplementaryoutputtransistors.Further,the The LM12 isa power op amp capableofdriving±25V IC withstandslargedifferentialinputvoltagesand is at ±10A whileoperatingfrom ±30V supplies.The wellbehaved should the common-mode range be monolithicIC can deliver80W of sinewave power exceeded. The IC delivers±10A outputcurrentat any output supplies,high-voltageregulators,high-qualityaudio voltageyetiscompletelyprotectedagainstoverloads, amplifiers,tape-headpositioners,x-yplottersorother includingshortsto the supplies.The dynamic safe- servo-controlsystems. area protectionis providedby instantaneouspeak- The LM12 issuppliedina four-lead,TO-220 packagetemperaturelimitingwithinthepower transistorarray. withV− on the case.A gold-eutecticdie-attachto a molybdenum interfaceis used to avoid thermal fatigueproblems.The LM12 is specifiedforeither militaryorcommercialtemperaturerange. Connection Diagram TypicalApplication* *Low distortion(0.01%)audioamplifier4-pinglassepoxy TO-3 socketisavailablefrom Figure1.AUGAT INC. Partnumber 8112-AG7 TO-220 Bottom View See Package Number NEP Pleasebe aware thatan importantnoticeconcerningavailability,standardwarranty,and use incriticalapplicationsof Texas Instrumentssemiconductorproductsand disclaimerstheretoappearsattheend ofthisdatasheet. 2Alltrademarksarethepropertyoftheirrespectiveowners. PRODUCTION DATA informationiscurrentas ofpublicationdate. Copyright© 1999–2013,Texas InstrumentsIncorporatedProductsconform to specificationsper the terms of the Texas Instrumentsstandardwarranty.Productionprocessingdoes not necessarilyincludetestingofallparameters.

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com These deviceshave limitedbuilt-inESD protection.The leadsshouldbe shortedtogetherorthedeviceplacedinconductivefoam duringstorageorhandlingtopreventelectrostaticdamage totheMOS gates. AbsoluteMaximum Ratings(1)(2) TotalSupplyVoltage(1) 80V InputVoltage See (3) OutputCurrent InternallyLimited JunctionTemperature See (4) StorageTemperatureRange −65°C to150°C Lead Temperature(Soldering,10 seconds) 300°C (1) Absolutemaximum ratingsindicatelimitsbeyond whichdamage tothedevicemay occur.The maximum voltageforwhichtheLM12 is ensuredtooperateisgivenintheoperatingratingsand inNote 4.Withinductiveloadsoroutputshorts,otherrestrictionsdescribedin applicationssectionapply. (2) IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheTexas InstrumentsSalesOffice/Distributorsforavailabilityand specifications. (3) Neitherinputshouldexceed thesupplyvoltageby more than50 voltsnorshouldthevoltagebetween one inputand any otherterminal exceed 60 volts. (4) Operatingjunctiontemperatureisinternallylimitednear225°C withinthepower transistorand 160°C forthecontrolcircuitry. OperatingRatings TotalSupplyVoltage 15V to60V Case Temperature(1) 0°C to70°C (1) The supplyvoltageis±30V (VMAX = 60V),unlessotherwisespecified.The voltageacrosstheconductingoutputtransistor(supplyto output)isVDISS and internalpower dissipationisPDISS.Temperaturerangeis0°C ≤ TC ≤ 70°C where TC isthecase temperature. Standardtypefaceindicateslimitsat25°C whileboldfacetypereferstolimitsor specialconditionsover fulltemperaturerange. Withno heatsink,thepackage willheatata rateof35°C/secper100W ofinternaldissipation.

2 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 ElectricalCharacteristics(1) LM12CLTypParameter Conditions Units25°C Limits InputOffsetVoltage ±10V ≤ VS ≤ ±0.5VMAX ,VCM = 0 2 15/20 mV (max) InputBiasCurrent V− + 4V ≤ VCM ≤ V+ −2V 0.15 0.7/1.0 μA (max) InputOffsetCurrent V− +4V ≤ VCM ≤ V+ −2V 0.03 0.2/0.3 μA (max) Common Mode Rejection V− +4V ≤ VCM ≤ V+ −2V 86 70/65 dB (min) Power SupplyRejection V+ = 0.5VMAX , 90 70/65 dB (min) V− = −0.5VMAX , 110 75/70 dB (min) 6V ≤ V+ ≤ 0.5VMAX OutputSaturationThreshold tON = 1 ms, ΔVIN = 5 (10 )mV, IOUT = 1A 1.8 2.2/2.5 V (max) 8A 4 5/7 V (max) 10A 5 V (max) LargeSignalVoltageGain tON = 2 ms, VSAT = 2V,IOUT = 0 100 30/20 V/mV (min) VSAT = 8V,R L = 4Ω 50 15/10 V/mV (min) ThermalGradientFeedback PDISS = 50W, tON = 65 ms 30 100 μV/W (max) Output-CurrentLimit tON = 10 ms, VDISS = 10V 13 16 A (max) tON = 100 ms, VDISS = 58V 1.5 0.9/0.6 A (min) 1.5 1.7 A (max) Power DissipationRating tON = 100 ms, VDISS = 20V 100 80/55 W (min) VDISS = 58V 80 52/35 W (min) DC ThermalResistance See (2)VDISS = 20V 2.3 2.9 °C/W (max) VDISS = 58V 2.7 4.5 °C/W (max) AC ThermalResistance See (2) 1.6 2.1 °C/W (max) SupplyCurrent VOUT = 0,IOUT = 0 60 120/140 mA (max) (1) The supplyvoltageis±30V (VMAX = 60V),unlessotherwisespecified.The voltageacrosstheconductingoutputtransistor(supplyto output)isVDISS and internalpower dissipationisPDISS.Temperaturerangeis0°C ≤ TC ≤ 70°C where TC isthecase temperature. Standardtypefaceindicateslimitsat25°C whileboldfacetypereferstolimitsor specialconditionsover fulltemperaturerange. Withno heatsink,thepackage willheatata rateof35°C/secper100W ofinternaldissipation. (2) Thisthermalresistanceisbased upon a peak temperatureof200°C inthecenterofthepower transistorand a case temperatureof 25°C measured atthecenterofthepackage bottom.The maximum junctiontemperatureofthecontrolcircuitrycan be estimatedbased upon a dc thermalresistanceof0.9°C/W oran ac thermalresistanceof0.6°C/W forany operatingvoltage. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 3 ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com Output-TransistorRatings(Ensured) Althoughtheoutputand supplyleadsareresistanttoelectrostaticdischargesfromhandling,theinputleadsarenot.The part shouldbe treatedaccordingly. Safe Area DC Thermal Resistance Figure2. Figure3. Pulse Thermal Resistance Figure4.

4 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 TypicalPerformance Characteristics Pulse Power Limit Pulse Power Limit Figure5. Figure6. Peak Output Current Output SaturationVoltage Figure7. Figure8. Large SignalResponse FollowerPulse Response Figure9. Figure10. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 5 ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com TypicalPerformance Characteristics(continued) Large SignalGain Thermal Response Figure11. Figure12. TotalHarmonic Distortion Frequency Response Figure13. Figure14. Output Impedance Power Supply Rejection Figure15. Figure16.

6 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 TypicalPerformance Characteristics(continued) InputBias Current InputNoise Voltage Figure17. Figure18. Common Mode Rejection Supply Current Figure19. Figure20. Supply Current Cross-SupplyCurrent Figure21. Figure22. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 7 ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com

APPLICATION INFORMATION

Twenty fiveyears ago the operationalamplifierwas a specializeddesign toolused primarilyforanalog computation.However, the availabilityof low costIC op amps inthe late1960'sprompted theiruse inrather mundane applications,replacinga few discretecomponents.Once a few basicprinciplesaremastered,op amps can be used togiveexceptionallygood resultsina wide range ofapplicationswhileminimizingbothcostand designeffort. The availabilityofa monolithicpower op amp now promisestoextendtheseadvantagestohigh-powerdesigns. Some conventionalapplicationsare givenhere to illustrateop amp designprinciplesas theyrelateto power circuitry.The inevitablefallinprices,as theeconomies ofvolume productionarerealized,willprompttheiruse in applicationsthatmight now seem trivial.Replacingsinglepower transistorswithan op amp willbecome economical because of improved performance,simplificationof attendantcircuitry,vastlyimproved fault protection,greaterreliabilityand thereductionofdesigntime. Power op amps introducenew factorsintothe designequation.With currenttransientsabove 10A, both the inductanceand resistanceofwireinterconnectsbecome importantina number ofways. Further,power ratings area crucialfactorindeterminingperformance.But thepower capabilityoftheIC cannotbe realizedunlessitis properlymounted toan adequateheatsink.Thus,thermaldesignisofmajorimportancewithpower op amps. Thisapplicationsummary startsoffby identifyingtheoriginofstrangeproblemsobservedwhileusingtheLM12 in a wide varietyof designswithallsortsof faultconditions.A few simpleprecautionswilleliminatethese problems.One would do wellto read the sectionon supply bypassing,lead inductance,output clamp diodes,ground loops and reactiveloadingbeforedoing any experimentation.Should therebe problems witherraticoperation,blow-outs,excessivedistortionor oscillation,anotherlook atthese sectionsisin order. The management and protectioncircuitrycan alsoaffectoperation.Should the totalsupplyvoltageexceed ratingsor drop below 15–20V, the op amp shutsoffcompletely.Case temperaturesabove 150°C alsocause shut down untilthe temperaturedrops to 145°C. This may take severalseconds,depending on the thermal system.Activationofthedynamic safe-areaprotectioncauses boththemain feedbacklooptolosecontroland a reductionin outputpower, withpossibleoscillations.In ac applications,the dynamic protectionwillcause waveform distortion.SincetheLM12 iswellprotectedagainstthermaloverloads,thesuggestionsfordetermining power dissipationand heatsinkrequirementsarepresentedlast. SUPPLY BYPASSING Allop amps shouldhave theirsupplyleadsbypassed withlow-inductancecapacitorshavingshortleadsand locatedcloseto the package terminalsto avoidspuriousoscillationproblems.Power op amps requirelarger bypass capacitors.The LM12 isstablewithgood-qualityelectrolyticbypass capacitorsgreaterthan20 μF.Other considerationsmay requirelargercapacitors. The currentin the supplyleads is a rectifiedcomponent of the load current.Ifadequate bypassingis not provided,thisdistortedsignalcan be fedback intointernalcircuitry.Low distortionathighfrequenciesrequires thatthesuppliesbe bypassedwith470 μF ormore,atthepackage terminals. LEAD INDUCTANCE Withordinaryop amps, lead-inductanceproblemsareusuallyrestrictedtosupplybypassing.Power op amps are alsosensitivetoinductanceintheoutputlead,particularlywithheavy capacitiveloading.Feedback totheinput shouldbe takendirectlyfrom the outputterminal,minimizingcommon inductancewiththe load.Sensing to a remote loadmust be accompanied by a high-frequencyfeedbackpath directlyfrom the outputterminal.Lead inductancecan alsocause voltagesurgeson thesupplies.Withlongleadstothepower source,energystoredin theleadinductancewhen theoutputisshortedcan be dumped back intothesupplybypass capacitorswhen the shortisremoved.The magnitudeofthistransientisreducedby increasingthesizeofthebypass capacitornear theIC.With20 μF localbypass,thesevoltagesurgesareimportantonlyiftheleadlengthexceeds a couplefeet (> 1 μH leadinductance).Twistingtogetherthesupplyand groundleadsminimizestheeffect.

8 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 GROUND LOOPS With fast,high-currentcircuitry,allsortsofproblemscan arisefrom impropergrounding.Ingeneral,difficulties can be avoidedby returningallgrounds separatelyto a common point.Sometimes thisisimpractical.When compromising,specialattentionshouldbe paidto the ground returnsforthe supplybypasses,loadand input signal.Ground planesalsohelptoprovidepropergrounding. Many problemsunrelatedtosystem performancecan be tracedtothegroundingofline-operatedtestequipment used forsystemcheckout.Hiddenpathsareparticularlydifficulttosortoutwhen severalpiecesoftestequipment are used but can be minimizedby using currentprobes or the new isolatedoscilloscopepre-amplifiers. Eliminatingany directground connectionbetween the signalgeneratorand the oscilloscopesynchronization inputsolvesone common problem. OUTPUT CLAMP DIODES When a push-pullamplifiergoes intopower limitwhiledrivingan inductiveload,thestoredenergyintheload inductancecan drivethe outputoutsidethe supplies.Althoughthe LM12 has internalclamp diodesthatcan handleseveralamperes fora few milliseconds,extremeconditionscan cause destructionoftheIC.The internal clamp diodesare imperfectinthatabout halfthe clamp currentflowsintothe supplyto which the outputis clamped whiletheotherhalfflowsacrossthesupplies.Therefore,theuse ofexternaldiodestoclamp theoutput tothepower suppliesisstronglyrecommended. Thisisparticularlyimportantwithhighersupplyvoltages. Experiencehas demonstratedthathard-wireshortingthe outputto the suppliescan inducerandom failuresif theseexternalclamp diodesarenotused and thesupplyvoltagesareabove ±20V. Thereforeitisprudenttouse outputclampdiodeseven when theloadisnotparticularlyinductive.Thisalsoappliestoexperimentalsetupsin thatblowoutshave been observedwhen diodeswere notused.Inpackaged equipment,itmay be possibleto eliminatethesediodes,providingthatfaultconditionscan be controlled. Heat sinkingoftheclamp diodesisusuallyunimportantinthattheyonlyclamp currenttransients.Forwarddrop with15A faulttransientsis of greaterconcern.Usually,these transientsdie out rapidly.The clamp to the negativesupplycan have somewhat reducedeffectivenessunderworstcase conditionsshouldtheforwarddrop exceed 1.0V.Mountingthisdiodetothepower op amp heatsinkimprovesthesituation.Althoughtheneed has onlybeen demonstratedwithsome motor loads,includinga thirddiode(D3 above)willeliminateany concern abouttheclamp diodes.Thisdiode,however,must be capableofdissipatingcontinuouspower as determinedby thenegativesupplycurrentoftheop amp. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 9 ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com REACTIVE LOADING The LM12 isnormallystablewithresistive,inductiveorsmallercapacitiveloads.Largercapacitiveloadsinteract withthe open-loopoutputresistance(about1Ω) to reduce the phase margin of the feedbackloop,ultimately causingoscillation.The criticalcapacitancedepends upon thefeedbackappliedaroundtheamplifier;a unity-gain followercan handleabout0.01μF, whilemore than1 μF does notcause problemsiftheloopgainisten.With loopgainsgreaterthanunity,a speedup capacitoracrossthefeedbackresistorwillaidstability.Inallcases,the op amp willbehave predictablyonlyifthesuppliesareproperlybypassed,groundloopsarecontrolledand high- frequencyfeedbackisderiveddirectlyfromtheoutputterminal,as recommended earlier. So-calledcapacitiveloadsare not always capacitive.A high-Q capacitorin combinationwithlong leadscan presenta series-resonantloadtotheop amp. Inpractice,thisisnotusuallya problem;butthesituationshould be keptinmind. Largecapacitiveloads(includingseries-resonant)can be accommodated by isolatingthefeedbackamplifierfrom the loadas shown above.The inductorgiveslow outputimpedance at lowerfrequencieswhileprovidingan isolatingimpedance athighfrequencies.The resistorkillstheQ ofseriesresonantcircuitsformedby capacitive loads.A low inductance,carbon-compositionresistorisrecommended. Optimum valuesofL and R depend upon thefeedbackgainand expectednatureoftheload,butarenotcritical.A 4 μH inductorisobtainedwith14 turns ofnumber 18 wire,closespaced,arounda one-inch-diameterform. The LM12 can be made stableforallloads witha largecapacitoron the output,as shown above. This compensationgivesthe lowestpossibleclosed-loopoutputimpedance at highfrequenciesand the bestload- transientresponse.Itisappropriateforsuch applicationsas voltageregulators. A feedbackcapacitor,C 1,isconnecteddirectlytotheoutputpinoftheIC.The outputcapacitor,C 2,isconnected attheoutputterminalwithshortleads.Single-pointgroundingtoavoiddc and ac groundloopsisadvised. The impedance,Z1,isthewireconnectingtheop amp outputtotheloadcapacitor.About 3-inchesofnumber-18 wire (70 nH) givesgood stabilityand 18-inches(400 nH) begins to degrade load-transientresponse.The minimum loadcapacitanceis47 μF, ifa solid-tantalumcapacitorwithan equivalentseriesresistance(ESR) of 0.1Ω isused.Electrolyticcapacitorswork as well,althoughcapacitancemay have tobe increasedto200 μF to bringESR below0.1Ω. Loop stabilityisnottheonlyconcernwhen op amps areoperatedwithreactiveloads.Withtime-varyingsignals, power dissipationcan alsoincreasemarkedly.Thisisparticularlytruewiththecombinationofcapacitiveloads and high-frequencyexcitation.

10 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 INPUT COMPENSATION The LM12 ispronetolow-amplitudeoscillationburstscoming outofsaturationifthehigh-frequencyloopgainis nearunity.The voltagefollowerconnectionismost susceptible.Thisglitchingcan be eliminatedattheexpense ofsmall-signalbandwidthusinginputcompensation.Inputcompensationcan alsobe used incombinationwith LR loadisolationtoimprovecapacitiveloadstability. An example ofa voltagefollowerwithinputcompensationisshown here.The R 2C 2 combinationacrosstheinput works withR 1 toreducefeedbackathighfrequencieswithoutgreatlyaffectingresponsebelow 100 kHz.A lead capacitor,C 1,improvesphase marginattheunity-gaincrossoverfrequency.Properoperationrequiresthatthe outputimpedance of the circuitrydrivingthe followerbe wellunder 1 kΩ at frequenciesup to a few hundred kilohertz. Extendinginputcompensationtotheintegratorconnectionisshown here.Both thefollowerand thisintegrator willhandle1 μF capacitiveloadingwithoutLR outputisolation. CURRENT DRIVE Thiscircuitprovidesan outputcurrentproportionaltotheinputvoltage.Currentdriveissometimes preferredfor servomotorsbecause itaidsinstabilizingtheservoloopby reducingphase lagcaused by motorinductance.In applicationsrequiringhighoutputresistance,such as operationalpower suppliesrunninginthecurrentmode, matchingof the feedbackresistorsto 0.01% isrequired.Alternately,an adjustableresistorcan be used for trimming. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 11 ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com PARALLEL OPERATION Outputdrivebeyond thecapabilityofone power amplifiercan be providedas shown here.The power op amps are wiredas followersand connectedin parallelwiththe outputscoupledthroughequalizationresistors.A standard,high-voltageop amp isused to providevoltagegain.Overallfeedbackcompensates forthe voltage droppedacrosstheequalizationresistors. Withparalleloperation,theremay be an increaseinunloadedsupplycurrentrelatedtotheoffsetvoltageacross theequalizationresistors.More outputbuffers,withindividualequalizationresistors,may be added tomeet even higherdriverequirements. This connectionallowsincreasedoutputcapabilitywithoutrequiringa separatecontrolamplifier.The output buffer,A2,providesloadcurrentthroughR 5 equaltothatsuppliedby themain amplifier,A1,throughR 4.Again, more outputbufferscan be added. Currentsharingamong paralleledamplifierscan be affectedby gain erroras the power-bandwidthlimitis approached.Inthefirstcircuit,theoperatingcurrentincreasewilldepend upon thematchingofhigh-frequency characteristics.Inthesecond circuit,however,theentireinputerrorofA2 appearsacrossR 4 and R 5.The supply currentincreasecan cause power limitingtobe activatedas theslew limitisapproached.Thiswillnotdamage theLM12. Itcan be avoidedinbothcases by connectingA1 as an invertingamplifierand restrictingbandwidth withC 1. SINGLE-SUPPLY OPERATION Althoughop amps are usuallyoperatedfrom dual supplies,single-supplyoperationispractical.This bridge amplifiersuppliesbi-directionalcurrentdrivetoa servomotorwhileoperatingfroma singlepositivesupply.The outputiseasilyconvertedtovoltagedriveby shortingR 6 and connectingR 7 totheoutputofA2,ratherthanA1.

12 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 Eitherinputmay be grounded,withbi-directionaldriveprovidedtotheother.Itisalsopossibletoconnectone inputtoa positivereference,withtheinputsignalvaryingaboutthisvoltage.Ifthereferencevoltageisabove 5V, R 2 and R 3 arenotrequired. HIGH VOLTAGE AMPLIFIERS The voltageswing deliveredto the loadcan be doubledby usingthe bridgeconnectionshown here.Output clampingtothesuppliescan be providedby usinga bridge-rectifierassembly. One limitationof the standardbridgeconnectionisthatthe loadcannotbe returnedto ground.Thiscan be circumventedby operatingthebridgewithfloatingsupplies,as shown above.For single-endeddrive,eitherinput can be grounded. Thiscircuitshows how two amplifierscan be cascaded todoubleoutputswing.The advantageoverthebridgeis thattheoutputcan be increasedwithany number ofstages,althoughseparatesuppliesarerequiredforeach. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 13 ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com Discretetransistorscan be used toincreaseoutputdriveto±70V at±10A as shown above.Withproperthermal design,theIC willprovidesafe-areaprotectionfortheexternaltransistors.Voltagegainisaboutthirty. OPERATIONAL POWER SUPPLY Note:SupplyvoltagesfortheLM318s are±15V Externalcurrentlimitcan be providedfora power op amp as shown above.The positiveand negativecurrent limitscan be setpreciselyand independently.Fastresponseisassuredby D 1 and D 2.Adjustmentrangecan be set down to zero withpotentiometersR 3 and R 7. Alternately,the limitcan be programmed from a voltage suppliedto R 2 and R 6. Thisisthe setup requiredforan operationalpower supplyor voltage-programmable power source.

14 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 SERVO AMPLIFIERS When making servosystems witha power op amp, thereisa temptationto use itforfrequencyshapingto stabilizetheservoloop.Sometimes thisworks;othertimestherearebetterways;and occasionallyitjustdoesn't fly.Usuallyit'sa matterofhow quicklyand towhat accuracytheservomust stabilize. Thismotor/tachometerservogivesan outputspeed proportionaltoinputvoltage.A low-levelop amp isused for frequencyshapingwhilethe power op amp providescurrentdriveto the motor.Currentdriveeliminatesloop phase shiftdue tomotorinductanceand makes high-performanceservoseasiertostabilize. Thispositionservouses an op amp todeveloptheratesignalelectricallyinsteadofusinga tachometer.Inhigh- performanceservos,ratesignalsmust be developedwithlargeerrorsignalswellbeyond saturationofthemotor drive.Using a separateop amp witha feedbackclamp allowsthe ratesignalto be developedproperlywith positionerrorsmore than an orderof magnitudebeyond the loop-saturationlevelas longas the photodiode sensorsarepositionedwiththisinmind. VOLTAGE REGULATORS An op amp can be used as a positiveornegativeregulator.Unlikemost regulators,itcan sinkcurrenttoabsorb energydumped back intotheoutput.Thispositiveregulatorhas a 0–50V outputrange. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 15 ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com Dual suppliesarenotrequiredtouse an op amp as a voltageregulatorifzerooutputisnotrequired.This4V to 50V regulatoroperatesfroma singlesupply.Shouldtheop amp notbe abletoabsorbenough energytocontrol an overvoltagecondition,a SCR willcrowbartheoutput. REMOTE SENSING Remote sensingas shown above allowstheop amp tocorrectfordc dropsincablesconnectingtheload.Even so,cabledropwillaffecttransientresponse.Degradationcan be minimizedby usingtwisted,heavy-gaugewires on theoutputline.Normally,common and one inputareconnectedtogetheratthesendingend. AUDIO AMPLIFIERS A power amplifiersuitableforuse inhigh-qualityaudioequipmentisshown above.Harmonic distortionisabout 0.01-percent.Intermodulationdistortion(60 Hz/7 kHz, 4:1)measured 0.015-percent.Transientresponse and saturationrecoveryareclean,and the9 V/μs slewrateoftheLM12 virtuallyeliminatestransientintermodulation distortion.Using separateamplifierstodrivelow-and high-frequencyspeakersgetsridofhigh-levelcrossover networksand attenuators.Further,itpreventsclippingon the low-frequencychannelfrom distortingthe high frequencies.

16 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 DETERMINING MAXIMUM DISSIPATION Itisa simplemattertoestablishpower requirementsforan op amp drivinga resistiveloadatfrequencieswell below 10 Hz. Maximum dissipationoccurswhen the outputisat one-halfthe supplyvoltagewithhigh-line conditions.The individualoutputtransistorsmust be ratedto handlethispower continuouslyat the maximum expectedcase temperature.The power ratingislimitedby themaximum junctiontemperatureas determinedby TJ = TC + PDISS θJC where

  • TC isthecase temperatureas measured atthecenterofthepackage bottom
  • PDISS isthemaximum power dissipation
  • θJC isthethermalresistanceattheoperatingvoltageoftheoutputtransistor (1) Recommended maximum junctiontemperaturesare200°C withinthepower transistorand 150°C forthecontrol circuitry. Ifthereisrippleon thesupplybus,itisvalidtouse theaveragevalueinworst-casecalculationsas longas the peak ratingofthepower transistorisnotexceeded attheripplepeak.With 120 Hz ripple,thisis1.5timesthe continuouspower rating. Dissipationrequirementsare notso easilyestablishedwithtimevaryingoutputsignals,especiallywithreactive loads.Both peak and continuousdissipationratingsmust be takenintoaccount,and thesedepend on thesignal waveform as wellas loadcharacteristics. With a sinewave output,analysisisfairlystraightforward.With supplyvoltagesof±VS,themaximum average power dissipationofbothoutputtransistorsis where
  • ZL isthemagnitudeoftheloadimpedance
  • θ itsphase angle (2) Maximum averagedissipationoccursbelowmaximum outputswingforθ < 40°. The instantaneouspower dissipationovertheconductinghalfcycleofone outputtransistorisshown here.Power dissipationisnearzeroon theotherhalfcycle.The outputlevelisthatresultinginmaximum peak and average dissipation.Plotsaregivenfora resistiveand a seriesRL load.The latterisrepresentativeofa 4Ω loudspeaker operatingbelow resonance and would be the worst case conditionin most audio applications.The peak dissipationofeach transistorisaboutfourtimesaverage.Inac applications,power capabilityisoftenlimitedby thepeak ratingsofthepower transistor. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 17 ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com The pulsethermalresistanceoftheLM12 isspecifiedforconstantpower pulseduration.Establishingan exact equivalencybetween constant-powerpulsesand thoseencounteredinpracticeisnot easy.However, forsine waves, reasonableestimatescan be made at any frequencyby assuming a constantpower pulseamplitude givenby: where

  • φ = 60°
  • θ istheabsolutevalueofthephase angleofZL (3) EquivalentpulsewidthistON ≃ 0.4τ forθ = 0 and tON ≃ 0.2τ forθ ≥ 20°, where τ isthe periodof the output waveform. DISSIPATION DRIVING MOTORS A motor witha lockedrotorlookslikean inductanceinserieswitha resistance,forpurposesof determining driverdissipation.With slow-responseservos,the maximum signalamplitudeat frequencieswhere motor inductanceissignificantcan be so smallthatmotorinductancedoes nothave tobe takenintoaccount.Ifthisis thecase,themotorcan be treatedas a simple,resistiveloadas longas therotorspeed islow enough thatthe back emf issmallby comparisontothesupplyvoltageofthedrivertransistor. A permanent-magnetmotor can buildup a back emf thatisequaltotheoutputswing oftheop amp drivingit. Reversingthismotor from fullspeed requiresthe outputdrivetransistorto operate,initially,alonga loadline based upon themotor resistanceand totalsupplyvoltage.Worst case,thisloadlinewillhave tobe withinthe continuousdissipationratingof the drivetransistor;but system dynamics may permittakingadvantageof the higherpulseratings.Motorinductancecan cause added stressifsystemresponseisfast. Shunt-and series-woundmotors can generateback emf'sthatare considerablymore than the totalsupply voltage,resultingineven higherpeak dissipationthana permanent-magnetmotorhavingthesame locked-rotor resistance. VOLTAGE REGULATOR DISSIPATION The pass transistordissipationof a voltageregulatoriseasilydeterminedin the operatingmode. Maximum continuousdissipationoccurswithhigh linevoltageand maximum load current.As discussedearlier,ripple voltagecan be averagedifpeak ratingsarenotexceeded;however,a higheraveragevoltagewillbe requiredto insurethatthepass transistordoes notsaturateattherippleminimum. Conditionsduringstart-upcan be more complex.Ifthe inputvoltageincreasesslowlysuch thatthe regulator does notgo intocurrentlimitchargingoutputcapacitance,thereare no problems.Ifnot,loadcapacitanceand loadcharacteristicsmust be takenintoaccount.Thisisalsothecase ifautomaticrestartisrequiredinrecovering fromoverloads. Automaticrestartor start-upwithfast-risinginputvoltagescannotbe ensuredunlessthecontinuousdissipation ratingof the pass transistoris adequate to supplythe load currentcontinuouslyat allvoltagesbelow the regulatedoutputvoltage.Inthisregard,theLM12 performsmuch betterthanIC regulatorsusingfoldbackcurrent limit,especiallywithhigh-lineinputvoltageabove 20V.

18 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 POWER LIMITING Shouldthepower ratingsoftheLM12 be exceeded,dynamic safe-areaprotectionisactivated.Waveforms with thispower limitingareshown fortheLM12 driving±26V at30 Hz into3Ω inserieswith24 mH (θ = 45°).Withan inductiveload,theoutputclamps tothesuppliesinpower limit,as above.Withresistiveloads,theoutputvoltage dropsinlimit.Behaviorwithmore complexRCL loadsisbetween theseextremes. Secondary thermallimitisactivatedshouldthecase temperatureexceed 150°C. Thisthermallimitshutsdown theIC completely(open output)untilthecase temperaturedropstoabout145°C. Recovery may takeseveral seconds. POWER SUPPLIES Power op amps do notrequireregulatedsupplies.However, theworst-caseoutputpower isdeterminedby the low-linesupplyvoltagein the rippletrough.The worst-casepower dissipationisestablishedby the average supplyvoltagewithhigh-lineconditions.The lossinpower outputthatcan be ensuredisthesquareoftheratio ofthesetwo voltages. Relativelysimpleoff-lineswitchingpower suppliescan providevoltageconversion,lineisolationand 5-percent regulationwhilereducingsizeand weight. The regulationagainstrippleand linevariationscan providea substantialincreaseinthepower outputthatcan be specifiedunder worst-caseconditions.Inaddition,switchingpower suppliescan convertlow-voltagepower sourcessuch as automotivebatteriesup toregulated,dual,high-voltagesuppliesoptimizedforpoweringpower op amps. HEAT SINKING A semiconductormanufacturerhas no controloverheatsinkdesign.Temperatureratingcan onlybe based upon case temperatureas measured atthecenterofthepackage bottom.Withpower pulsesoflongerdurationthan 100 ms, case temperatureisalmostentirelydependenton heatsinkdesignand themountingoftheIC tothe heatsink. The design of heat sink is beyond the scope of thiswork. Convection-cooledheat sinks are available commercially,and theirmanufacturersshouldbe consultedforratings.The precedingfigureisa roughguidefor temperatureriseas a functionoffinarea(bothsides)availableforconvectioncooling. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 19 ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com PropermountingoftheIC isrequiredtominimizethethermaldropbetween thepackage and theheatsink.The heat sinkmust alsohave enough metalunder the package to conductheat from the centerof the package bottomtothefinswithoutexcessivetemperaturedrop. A thermalgrease such as Wakefieldtype120 or ThermalloyThermacote shouldbe used when mountingthe package to the heat sink.Withoutthiscompound, thermalresistancewillbe no betterthan 0.5°C/W, and probablymuch worse.With the compound, thermalresistancewillbe 0.2°C/W or less,assuming under 0.005 inchcombined flatnessrunoutforthepackage and heatsink.Propertorquingofthemountingboltsisimportant. Fourtosixinch-poundsisrecommended. Should itbe necessaryto isolateV− from the heat sink,an insulatingwasher isrequired.Hard washers like beryliumoxide,anodizedaluminum and mica requiretheuse ofthermalcompound on bothfaces.Two-milmica washers are most common, givingabout 0.4°C/W interfaceresistancewiththe compound. Silicone-rubber washers arealsoavailable.A 0.5°C/W thermalresistanceisclaimedwithoutthermalcompound. Experiencehas shown thattheserubberwashersdeteriorateand must be replacedshouldtheIC be dismounted. “Isostrate”insulatingpads forfour-leadTO-220 packagesareavailablefromPower Devices,Inc.Thermalgrease isnotrequired,and theinsulatorsshouldnotbe reused. DefinitionofTerms Inputoffsetvoltage:The absolutevalueofthevoltagebetween theinputterminalswiththeoutputvoltageand currentatzero. Inputbiascurrent:The absolutevalueoftheaverageofthetwo inputcurrentswiththeoutputvoltageand currentatzero. Inputoffsetcurrent:The absolutevalueofthedifferenceinthetwo inputcurrentswiththeoutputvoltageand currentatzero. Common-mode rejection:The ratiooftheinputvoltagerangetothechange inoffsetvoltagebetween the extremes. Supply-voltagerejection:The ratioofthespecifiedsupply-voltagechange tothechange inoffsetvoltage between theextremes. Output saturationthreshold:The outputswinglimitfora specifiedinputdrivebeyond thatrequiredforzero output.Itismeasured withrespecttothesupplytowhichtheoutputisswinging. Large signalvoltagegain: The ratiooftheoutputvoltageswingtothedifferentialinputvoltagerequiredto drivetheoutputfromzerotoeitherswinglimit.The outputswinglimitisthesupplyvoltagelessa specified quasi-saturationvoltage.A pulseofshortenough durationtominimizethermaleffectsisused as a measurement signal. Thermal gradientfeedback: The inputoffsetvoltagechange caused by thermalgradientsgeneratedby heatingoftheoutputtransistors,butnotthepackage.Thiseffectisdelayedby severalmillisecondsand resultsinincreasedgainerrorbelow100 Hz. Output-currentlimit:The outputcurrentwitha fixedoutputvoltageand a largeinputoverdrive.The limiting currentdropswithtimeonce theprotectioncircuitryisactivated. Power dissipationrating:The power thatcan be dissipatedfora specifiedtimeintervalwithoutactivatingthe protectioncircuitry.Fortimeintervalsinexcessof100 ms, dissipationcapabilityisdeterminedby heat sinkingoftheIC package ratherthanby theIC itself. Thermal resistance:The peak,junction-temperaturerise,perunitofinternalpower dissipation,above thecase temperatureas measured atthecenterofthepackage bottom.The dc thermalresistanceapplieswhen one outputtransistorisoperatingcontinuously.The ac thermalresistanceapplieswiththeoutput transistorsconductingalternatelyata highenough frequencythatthepeak capabilityofneithertransistor isexceeded. Supply current:The currentrequiredfromthepower sourcetooperatetheamplifierwiththeoutputvoltage and currentatzero.

20 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL www.ti.com SNOSBY8D –MAY 1999–REVISED APRIL 2013 EquivalentSchematic (excludingactiveprotectioncircuitry) Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 21 ProductFolderLinks:K04RLM12 LM12CL

K04RLM12,LM12CL SNOSBY8D –MAY 1999–REVISED APRIL 2013 www.ti.com

REVISION HISTORY

Changes from RevisionC (April2013)toRevisionD Page

22 SubmitDocumentationFeedback Copyright© 1999–2013,Texas InstrumentsIncorporated

ProductFolderLinks:K04RLM12 LM12CL

Texas InstrumentsIncorporatedand itssubsidiaries(TI)reservetherighttomake corrections,enhancements,improvementsand other changes toitssemiconductorproductsand servicesperJESD46, latestissue,and todiscontinueany productorserviceperJESD48, latest issue.Buyersshouldobtainthelatestrelevantinformationbeforeplacingordersand shouldverifythatsuch informationiscurrentand complete.Allsemiconductorproducts(alsoreferredtohereinas “components”)aresoldsubjecttoTI’s termsand conditionsofsale suppliedatthetimeoforderacknowledgment. TIwarrantsperformanceofitscomponents tothespecificationsapplicableatthetimeofsale,inaccordancewiththewarrantyinTI’s terms and conditionsofsaleofsemiconductorproducts.Testingand otherqualitycontroltechniquesareused totheextentTIdeems necessary tosupportthiswarranty.Exceptwhere mandated by applicablelaw,testingofallparametersofeach component isnotnecessarily performed. TIassumes no liabilityforapplicationsassistanceorthedesignofBuyers’products.Buyersareresponsiblefortheirproductsand applicationsusingTIcomponents.To minimizetherisksassociatedwithBuyers’productsand applications,Buyersshouldprovide adequatedesignand operatingsafeguards. TIdoes notwarrantorrepresentthatany license,eitherexpressorimplied,isgrantedunderany patentright,copyright,mask work right,or otherintellectualpropertyrightrelatingtoany combination,machine,orprocessinwhichTIcomponents orservicesareused.Information publishedby TIregardingthird-partyproductsorservicesdoes notconstitutea licensetouse such productsorservicesora warrantyor endorsementthereof.Use ofsuch informationmay requirea licensefroma thirdpartyunderthepatentsorotherintellectualpropertyofthe thirdparty,ora licensefromTIunderthepatentsorotherintellectualpropertyofTI. ReproductionofsignificantportionsofTIinformationinTIdatabooks ordatasheetsispermissibleonlyifreproductioniswithoutalteration and isaccompaniedby allassociatedwarranties,conditions,limitations,and notices.TIisnotresponsibleorliableforsuch altered documentation.Informationofthirdpartiesmay be subjecttoadditionalrestrictions. ResaleofTIcomponents orserviceswithstatementsdifferentfromorbeyond theparametersstatedby TIforthatcomponent orservice voidsallexpressand any impliedwarrantiesfortheassociatedTIcomponent orserviceand isan unfairand deceptivebusinesspractice. TIisnotresponsibleorliableforany such statements. Buyeracknowledgesand agreesthatitissolelyresponsibleforcompliancewithalllegal,regulatoryand safety-relatedrequirements concerningitsproducts,and any use ofTIcomponents initsapplications,notwithstandingany applications-relatedinformationorsupport thatmay be providedby TI.Buyerrepresentsand agreesthatithas allthenecessaryexpertisetocreateand implementsafeguardswhich anticipatedangerousconsequencesoffailures,monitorfailuresand theirconsequences,lessenthelikelihoodoffailuresthatmightcause harm and takeappropriateremedialactions.BuyerwillfullyindemnifyTIand itsrepresentativesagainstany damages arisingoutoftheuse ofany TIcomponents insafety-criticalapplications. Insome cases,TIcomponents may be promotedspecificallytofacilitatesafety-relatedapplications.Withsuch components,TI’s goalisto helpenablecustomerstodesignand createtheirown end-productsolutionsthatmeet applicablefunctionalsafetystandardsand requirements.Nonetheless,such components aresubjecttotheseterms. No TIcomponents areauthorizedforuse inFDA ClassIII(orsimilarlife-criticalmedicalequipment)unlessauthorizedofficersoftheparties have executeda specialagreementspecificallygoverningsuch use. OnlythoseTIcomponents whichTIhas specificallydesignatedas militarygradeor“enhanced plastic”aredesignedand intendedforuse in military/aerospaceapplicationsorenvironments.Buyeracknowledgesand agreesthatany militaryoraerospaceuse ofTIcomponents whichhave not been so designatedissolelyattheBuyer's risk,and thatBuyerissolelyresponsibleforcompliancewithalllegaland regulatoryrequirementsinconnectionwithsuch use. TIhas specificallydesignatedcertaincomponents as meetingISO/TS16949 requirements,mainlyforautomotiveuse.Inany case ofuse of non-designatedproducts,TIwillnotbe responsibleforany failuretomeet ISO/TS16949. Products Applications Audio www.ti.com/audio Automotiveand Transportationwww.ti.com/automotive Amplifiers amplifier.ti.com Communicationsand Telecom www.ti.com/communications Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers DLP ® Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps DSP dsp.ti.com Energyand Lighting www.ti.com/energy Clocksand Timers www.ti.com/clocks Industrial www.ti.com/industrial Interface interface.ti.com Medical www.ti.com/medical Logic logic.ti.com Security www.ti.com/security Power Mgmt power.ti.com Space,Avionicsand Defense www.ti.com/space-avionics-defense Microcontrollers microcontroller.ti.com Videoand Imaging www.ti.com/video RFID www.ti-rfid.com OMAP ApplicationsProcessors www.ti.com/omap TIE2E Community e2e.ti.com WirelessConnectivity www.ti.com/wirelessconnectivity MailingAddress:Texas Instruments,PostOfficeBox 655303,Dallas,Texas 75265 Copyright© 2013,Texas InstrumentsIncorporated