Tkool Electronics

I.IntroductionGroundpenetratingradar(GPR)hasbeenwidelyusedinmanyfieldsduetoitsnon-destructivedetectioncharacteristics.Itsdetectionprincipleis:useanantennatotransmithigh-frequencybroadbandelectromagneticwavestotheground,andthenreceivethereflectedechofromtheinterfaceoftheundergroundmedium.Throughtheprocessingandanalysisoftheechosignal,inferthestructureoftheundergroundmedium.Theimpactgroundpenetratingradarhasreceivedextensiveattentionduetoitssimplestructureandrichechoinformation.Thegroundpenetratingradarmentionedbelowreferstotheimpactgroundpenetratingradar.Duetothesharplossonthepropagationpath,thedynamicrangeoftheechosignalreceivedbytheantennaisextremelylarge,generallyupto150dB.ThedynamicrangeoftheA/Dconverterintheradarreceivingsystemcangenerallyonlyreach80-90dB,whichisdifficulttomeettherequirementsoftheradarsystem.Atthesametime,duetothesmallechoamplitudeofdeeptargets,thedetectiondepthandresolutionofthegroundpenetratingradarwillbeseriouslyaffectedifitisnotprocessed.Inordertoimprovethedetectiondepthandresolutionoftheradar,andatthesametimeincreasethedynamicrangeofthereceivingsystem,thisarticleusesAD603todesignatime-varyinggainamplifiertoprocesstheechosignal,andgivedifferentgainstotheechosignalatdifferenttimes.TocompensatethelackofthedynamicrangeoftheA/Dconverter,andachievethepurposeofmatchingthedynamicrangeoftheechosignal.CatalogI.IntroductionII.DesignofTime-varyingGainAmplifierIII.DesignoftheZeroAdjustmentCircuitoftheTime-varyingGainAmplifierIV.MeasuredResultsV.ConclusionFAQOrdering&QuantityII.DesignofTime-varyingGainAmplifierTheso-calledtime-varyinggainamplifiersimplymeansthatthegainoftheamplifierisafunctionoftime.Sinceinthegroundpenetratingradarsystem,timeactuallycorrespondstothedistancebetweenthetargetandtheantenna,fromthisperspective,intheradarsystem,itcanbecalledarangegainamplifier.Themechanismofactionistouseattenuationorlowergainamplificationforthescatteredechoesofnear-distancetargets,andusehighergainamplificationforthescatteredechoesoflong-distancetargets,sothattheechosignalsenteringthedataacquisitioncircuitbecomerelativelystable.Intheend,thestrongsignaloftheshallowtargetechoisattenuatedorsuppressedtoavoidtheamplifierfrombeingsaturatedandoverloadedortheamplifieroutputexceedstheinputrangeoftheA/Dconverter;theweaksignalofthedeeptargetechoiseffectivelyamplifiedtoensuretheacquisitionanddiscernmentofthetargetsignal.Therearemanyschemesfordesigningtime-varyinggainamplifiers.Inviewoftherequirementsofgroundpenetratingradarsystem,thisarticleusesthenewvoltage-controlledamplifierAD603producedbyAmericanAnalogDevicestorealizethetime-varyinggainamplifier.TheadvantagesofAD603are:lownoise,wideband,gain,gainrangeareadjustable,thegainvaluechangeslinearlywiththeexternalcontrolvoltage,andthebandwidthdoesnotchangewiththegain,etc.,whichcanfullymeettherequirementsoftheradarsystem.TheschematicdiagramisshowninFigure1.Figure1AD603schematicdiagramItcanbeseenfromtheschematicdiagramthattheinternalstructureofAD603isdividedinto3functionalareas:gaincontrolarea;precisionpassiveinputattenuationarea;fixedgainoperationalamplifierarea.Thecontrolvoltageinthegaincontrolareacontrolsthecontinuousattenuationoftheattenuator.Itislikeslidingthearrowonthenon-invertingendofthefixedgainopampinthefigurebetween0and-42.14dB.ThegainrangeandbandwidthofAD603aredeterminedbytheconnectionmodeofVOUTandFDBK.WhenVOUTandFDBKareshort-circuited,thegainrangeis10~30dB,andthebandwidthis90MHz;whentheoutputterminalVOUTandthefeedbackterminalFDBKhaveanindirect2.15kresistance.WhenthefeedbackterminalFDBKisgroundedthrough5.6pF,thegainrangeis0~40dB,frequencybandwidthis30MHz;whenVOUTandFDBKareopen,andthefeedbackterminalFDBKisgroundedthrough18pF,thegainrangeis10-50dBandthefrequencybandwidthis9MHz.Oncethegainrangeisdetermined,thebandwidthoftheentireamplifierisalsodetermined.Andwithinthegainrange,thebandwidthdoesnotchangewiththegain.ThisisbecausethegainadjustmentisrealizedbytheR-2Rladderresistanceattenuationnetworkbeforethefixedgainopamp,insteadofchangingthefeedbackresistanceoftheopamp,sothebandwidthoftheentireamplifierisnotaffectedbythegainadjustment.Sincethedynamicrangeofthegroundpenetratingradarechosignalisextremelylarge,inordertoprovidealargergaintotheweakechosignalinthedeeplayer,forsubsequentdataacquisitionandprocessing.Inthespecificimplementation,atwo-stageAD603cascademethodisusedtorealizevariablegainamplification,andthegainrangeofthefrontandbackstagesissetto0-40dB.Inthisway,thetwo-stageamplifyingcircuitcanprovideatotalvariablegainrangeof0-80dB,whichcanmeettheneedsofthegroundpenetratingradartoexpandthedynamicrange.Atthesametime,inordertoimprovethesignal-to-noiseratioofthetwo-stageamplifiercircuitasmuchaspossibleandreducethepossibilitythatthenoisegeneratedbythepreviousamplifierisamplifiedbythelatteramplifier,thetwo-stageamplifieradoptsasequentialcontrolconnectionmethod.ThecircuitprincipleisshowninFigure2.Figure2SchematicdiagramofvariablegainamplifiercircuitInordertominimizethefrequencybandlossafterthecascadeofthetwo-stageamplifier,improvethelow-frequencyresponsecharacteristicsoftheamplifier,andavoidthelossoflow-frequencycomponentsinthegroundpenetratingradarechosignal,thedirectcouplingmethodisselectedinthedesign.Asthegainchangerangeofthesingle-stageamplifierissetto0~40dB,itsbandwidthis30MHz.Afterthetwo-stageamplifieriscascaded,thetotalamplifier3dBbandwidthwillbereduced,andthebandwidthatthistimeisabout21MHz,butthedynamicrangeisimproved.Foragroundpenetratingradarwithanantennacenterfrequencyof100MHz,thehighestfrequencycomponentofitsechosignalisabout150MHz.Assumingthatthetransmittedpulserepetitionfrequencyis300kHzandthesamplingtimeintervalis0.1ns,thehighestfrequencycomponentoftheechosignalafterequivalentsamplingtransformationcanbeobtainedas:Itcanbeseenthatthehighestfrequencycomponentofthesignalaftersamplingandtransformationismuchsmallerthanthebandwidthoftheamplifier,whichcanensurethatthesignalisamplifiedwithoutfrequencydistortion。

STM32F769BIT6-208-LQFP-STMicroelectronics

I.IntroductionGroundpenetratingradar(GPR)hasbeenwidelyusedinmanyfieldsduetoitsnon-destructivedetectioncharacteristics.Itsdetectionprincipleis:useanantennatotransmithigh-frequencybroadbandelectromagneticwavestotheground,andthenreceivethereflectedechofromtheinterfaceoftheundergroundmedium.Throughtheprocessingandanalysisoftheechosignal,inferthestructureoftheundergroundmedium.Theimpactgroundpenetratingradarhasreceivedextensiveattentionduetoitssimplestructureandrichechoinformation.Thegroundpenetratingradarmentionedbelowreferstotheimpactgroundpenetratingradar.Duetothesharplossonthepropagationpath,thedynamicrangeoftheechosignalreceivedbytheantennaisextremelylarge,generallyupto150dB.ThedynamicrangeoftheA/Dconverterintheradarreceivingsystemcangenerallyonlyreach80-90dB,whichisdifficulttomeettherequirementsoftheradarsystem.Atthesametime,duetothesmallechoamplitudeofdeeptargets,thedetectiondepthandresolutionofthegroundpenetratingradarwillbeseriouslyaffectedifitisnotprocessed.Inordertoimprovethedetectiondepthandresolutionoftheradar,andatthesametimeincreasethedynamicrangeofthereceivingsystem,thisarticleusesAD603todesignatime-varyinggainamplifiertoprocesstheechosignal,andgivedifferentgainstotheechosignalatdifferenttimes.TocompensatethelackofthedynamicrangeoftheA/Dconverter,andachievethepurposeofmatchingthedynamicrangeoftheechosignal.CatalogI.IntroductionII.DesignofTime-varyingGainAmplifierIII.DesignoftheZeroAdjustmentCircuitoftheTime-varyingGainAmplifierIV.MeasuredResultsV.ConclusionFAQOrdering&QuantityII.DesignofTime-varyingGainAmplifierTheso-calledtime-varyinggainamplifiersimplymeansthatthegainoftheamplifierisafunctionoftime.Sinceinthegroundpenetratingradarsystem,timeactuallycorrespondstothedistancebetweenthetargetandtheantenna,fromthisperspective,intheradarsystem,itcanbecalledarangegainamplifier.Themechanismofactionistouseattenuationorlowergainamplificationforthescatteredechoesofnear-distancetargets,andusehighergainamplificationforthescatteredechoesoflong-distancetargets,sothattheechosignalsenteringthedataacquisitioncircuitbecomerelativelystable.Intheend,thestrongsignaloftheshallowtargetechoisattenuatedorsuppressedtoavoidtheamplifierfrombeingsaturatedandoverloadedortheamplifieroutputexceedstheinputrangeoftheA/Dconverter;theweaksignalofthedeeptargetechoiseffectivelyamplifiedtoensuretheacquisitionanddiscernmentofthetargetsignal.Therearemanyschemesfordesigningtime-varyinggainamplifiers.Inviewoftherequirementsofgroundpenetratingradarsystem,thisarticleusesthenewvoltage-controlledamplifierAD603producedbyAmericanAnalogDevicestorealizethetime-varyinggainamplifier.TheadvantagesofAD603are:lownoise,wideband,gain,gainrangeareadjustable,thegainvaluechangeslinearlywiththeexternalcontrolvoltage,andthebandwidthdoesnotchangewiththegain,etc.,whichcanfullymeettherequirementsoftheradarsystem.TheschematicdiagramisshowninFigure1.Figure1AD603schematicdiagramItcanbeseenfromtheschematicdiagramthattheinternalstructureofAD603isdividedinto3functionalareas:gaincontrolarea;precisionpassiveinputattenuationarea;fixedgainoperationalamplifierarea.Thecontrolvoltageinthegaincontrolareacontrolsthecontinuousattenuationoftheattenuator.Itislikeslidingthearrowonthenon-invertingendofthefixedgainopampinthefigurebetween0and-42.14dB.ThegainrangeandbandwidthofAD603aredeterminedbytheconnectionmodeofVOUTandFDBK.WhenVOUTandFDBKareshort-circuited,thegainrangeis10~30dB,andthebandwidthis90MHz;whentheoutputterminalVOUTandthefeedbackterminalFDBKhaveanindirect2.15kresistance.WhenthefeedbackterminalFDBKisgroundedthrough5.6pF,thegainrangeis0~40dB,frequencybandwidthis30MHz;whenVOUTandFDBKareopen,andthefeedbackterminalFDBKisgroundedthrough18pF,thegainrangeis10-50dBandthefrequencybandwidthis9MHz.Oncethegainrangeisdetermined,thebandwidthoftheentireamplifierisalsodetermined.Andwithinthegainrange,thebandwidthdoesnotchangewiththegain.ThisisbecausethegainadjustmentisrealizedbytheR-2Rladderresistanceattenuationnetworkbeforethefixedgainopamp,insteadofchangingthefeedbackresistanceoftheopamp,sothebandwidthoftheentireamplifierisnotaffectedbythegainadjustment.Sincethedynamicrangeofthegroundpenetratingradarechosignalisextremelylarge,inordertoprovidealargergaintotheweakechosignalinthedeeplayer,forsubsequentdataacquisitionandprocessing.Inthespecificimplementation,atwo-stageAD603cascademethodisusedtorealizevariablegainamplification,andthegainrangeofthefrontandbackstagesissetto0-40dB.Inthisway,thetwo-stageamplifyingcircuitcanprovideatotalvariablegainrangeof0-80dB,whichcanmeettheneedsofthegroundpenetratingradartoexpandthedynamicrange.Atthesametime,inordertoimprovethesignal-to-noiseratioofthetwo-stageamplifiercircuitasmuchaspossibleandreducethepossibilitythatthenoisegeneratedbythepreviousamplifierisamplifiedbythelatteramplifier,thetwo-stageamplifieradoptsasequentialcontrolconnectionmethod.ThecircuitprincipleisshowninFigure2.Figure2SchematicdiagramofvariablegainamplifiercircuitInordertominimizethefrequencybandlossafterthecascadeofthetwo-stageamplifier,improvethelow-frequencyresponsecharacteristicsoftheamplifier,andavoidthelossoflow-frequencycomponentsinthegroundpenetratingradarechosignal,thedirectcouplingmethodisselectedinthedesign.Asthegainchangerangeofthesingle-stageamplifierissetto0~40dB,itsbandwidthis30MHz.Afterthetwo-stageamplifieriscascaded,thetotalamplifier3dBbandwidthwillbereduced,andthebandwidthatthistimeisabout21MHz,butthedynamicrangeisimproved.Foragroundpenetratingradarwithanantennacenterfrequencyof100MHz,thehighestfrequencycomponentofitsechosignalisabout150MHz.Assumingthatthetransmittedpulserepetitionfrequencyis300kHzandthesamplingtimeintervalis0.1ns,thehighestfrequencycomponentoftheechosignalafterequivalentsamplingtransformationcanbeobtainedas:Itcanbeseenthatthehighestfrequencycomponentofthesignalaftersamplingandtransformationismuchsmallerthanthebandwidthoftheamplifier,whichcanensurethatthesignalisamplifiedwithoutfrequencydistortion。

IntroductionLM567isahigh-stabilitylow-frequencyintegratedphase-lockedloopdecoder.Duetoitsgoodnoisesuppressionabilityandcenterfrequencystability,itiswidelyusedinthedecodingofvariouscommunicationequipmentandthedemodulationcircuitofAMandFMsignals.LM567Imagesareforreferenceonly.LM567ToneDecoderCatalogIntroductionDocumentsandMediaPinConfigurationandFunctionsBasicParametersFeaturesApplicationsFunctionalBlockDiagramCircuitDiagramECCNUNSPSCProductManufacturerProductRangeOrdering&QuantityDocumentsandMediaComponentDatasheetsLM567(C)PinConfigurationandFunctionsThedatasheetprovidedaboveisforyourreference,sothatyoucanunderstandthephysicaldimensionsofallpackagesinmoredetail.Theconfigurationofall8pinsandthefunctionofeachpinareasfollows:PinConfigurationAndthefunctionofall8pinsandthefunctionofeachpinareasfollows:PinFunctionBasicParametersBrandNameTexasInstrumentsECCNCodeEAR99FactoryLeadTime1WeekHTSCode8542.39.00.01JESD-30CodeR-PDSO-G8JESD-609Codee3Length4.9mmManufacturerTexasInstrumentsManufacturerPartNumberLM567CMX/NOPBMoistureSensitivityLevel1NumberofFunctions1NumberofTerminals8OperatingTemperature-Max70CPackageBodyMaterialPLASTIC/EPOXYPackageCodeSOPPackageDescriptionSOP-8PackageEquivalenceCodeSOP8,.23PackageShapeRECTANGULARPackageStyleSMALLOUTLINEPartLifeCycleCodeActivePartPackageCodeSOICPbfreeCodeYesPeakReflowTemperature260℃PinCount8QualificationStatusNotQualifiedReachComplianceCodeCompliantRiskRank0.62RohsCodeYesSeatedHeight-Max1.75mmSupplyCurrent-Max15mASupplyVoltage-Nom5VSurfaceMountYESTelecomICTypeTONEDECODERCIRCUITTemperatureGradeCOMMERCIALTerminalFinishMatteTin(Sn)TerminalFormGULLWINGTerminalPitch1.27mmTerminalPositionDUALTime@PeakReflowTemperature-Max(s)NOTSPECIFIEDWidth3.91mmFeatures20to1FrequencyRangeWithanExternalResistorLogicCompatibleOutputWith100-mACurrentSinkingCapabilityBandwidthAdjustableFrom0to14%HighRejectionofOutofBandSignalsandNoiseImmunitytoFalseSignalsHighlyStableCenterFrequencyCenterFrequencyAdjustablefrom0.01Hzto500kHzApplicationsTheLM567tonedecoderisadevicecapableofdetectingwhetheraninputsignaliswithinaselectabledetectionrange.Thedevicehasanopencollectortransistoroutput,soanexternalresistorisrequiredtoreachtheappropriatelogiclevels.Whentheinputsignalisinthedetectionband,thedeviceoutputchangestotheLOWstate.TheinternalfreeoperatingfrequencyoftheVCOdefinesthecenterfrequencyofthedetectionband.AnexternalRCfilterisrequiredtoadjustthisfrequency.Thebandwidthinwhichthedevicewilldetectthedesiredfrequencydependsonthecapacityoftheloopfilterterminal.Usuallya1Fcapacitorisconnectedtothispin.LM567isgenerallyusedinthefollowingsituations:TouchToneDecodingPrecisionOscillatorFrequencyMonitoringandControlWideBandFSKDemodulationUltrasonicControlsCarrierCurrentRemoteControlsCommunicationsPagingDecodersFunctionalBlockDiagramCircuitDiagramThefollowingdescribestheclassiccircuitdiagramofthephase-lockedloopLM567usedincarriercommunicationapplications.Therearemanyapplicationsforit,butthethreecircuitsdescribedbelowhaveallbeentestedbypracticeforreferencebythosewholovecarriercommunication.ClassicCircuitDiagram(1)ClassicCircuitDiagram(2)ClassicCircuitDiagram(3)ECCNUNSPSCDescriptionValueECCNCodeEAR99HTSCode8542.39.00.01ProductManufacturerTexasInstrumentsInc.(TI)isanAmericantechnologycompanythatdesignsandmanufacturessemiconductorsandvariousintegratedcircuits,whichitsellstoelectronicsdesignersandmanufacturersglobally.ItsheadquartersareinDallas,Texas,UnitedStates.TIisoneofthetoptensemiconductorcompaniesworldwide,basedonsalesvolume.TexasInstrumentssfocusisondevelopinganalogchipsandembeddedprocessors,whichaccountsformorethan80%oftheirrevenue.TIalsoproducesTIdigitallightprocessing(DLP)technologyandeducationtechnologyproductsincludingcalculators,microcontrollersandmulti-coreprocessors.Todate,TIhasmorethan43,000patentsworldwide.ProductRangeDevicesBoardsDeveloperToolsARMPROCESSORSAUTOMOTIVEPRODUCTSIDENTIFICATIONSECURITYKinetisCortex-MMicrocontrollersIn-VehicleNetworkNFCLPCCortex-MMicrocontrollersMicrocontrollersandProcessorsRFIDAfterreadingtheblog,haveyoubetterunderstandLM567?IfyouarealsointerestedinhowtouseLM567totestthespeedofyourmotorcycle,youmaywishtobrowserighthererightnow!Finally,ifyouhaveanyquestionsaboutLM567,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!IIntroductionLM567isatonedecodingphase-lockedloopintegratedcircuit.Itiscompactindesign,simpleincircuit,andhasawiderangeofapplications.However,ifusingimproperly,itwillbringtroublesindebugging.ThisblogintroducestheworkingprincipleandtipsabouthowtouseLM567tonedecoderforreadersreference.Figure1.LM567ToneDecoderCatalogIIntroductionIILM567InternalStructurePinFunctionIIILM567WorkingPrincipleApplicationIVTipsofUsingToneDecoderLM567Ordering&QuantityIILM567InternalStructurePinFunctionThenameofLM567isphase-lockedlooptonedecoder,itspackageformuses8-pindualin-line,itsinternalstructureandpinfunctionsareillustratedinFigure2.Itsinternalcircuitstructureiscomposedofquadraturephase,detector,phase-lockedloop,amplifier,etc.TheoperatingvoltagerangeofLM567is4.75-9V,theoperatingfrequencycanreach500KHz,andthestaticoperatingcurrentisonly8mA.Thepin③isthesignalinputterminal,whichrequirestheinputsignaltobegreaterthan25mV.Thepin⑧isthelogicoutputterminal.Itcanbeseenfromthefigurethatitisanopencollectortransistoroutput,whichallowsamaximumsinkcurrentof100mA.Theexternalresistanceandcapacitanceofpins⑤and⑥determinethecenterfrequencyf01/1.1RCofICinternalvoltagecontrolledoscillator.Pins①and②areusuallyconnectedtothegroundseparatelytoformanoutputfilternetworkandalooplow-passfilternetwork.Thecapacitorconnectedtopin②determinesthecapturebandwidth.Thelargerthevalueofthecapacitor,thenarrowertheloopbandwidthis.Figure2.TopViewofLM567IIILM567WorkingPrincipleApplicationWhenthetonedecoderLM567works,itsphase-lockedloopinternalcurrent-controlledoscillatorgeneratesanoscillationsignalofacertainfrequencyandphase.Thissignalissenttothequadraturephasedetectortogetherwiththesignalinputatpin③forcomparison.Whenthefrequencyofthesignalfallswithinagivenpassband,thephase-lockedlooplocksthissignal,andatthesametimetheinternaltransistoroftheLM567iscontrolledtobepoweredup,andtheoutputterminaloftheLM567outputslowlevel.The⑤pinofLM567outputstherectangularsignaloftheinternaloscillator,andthe⑥pinoutputsthesawtoothpulse.Thefrequencyofbothisthesameasthecenterfrequencyoftheinternaloscillator.The②pinistheoutputofthephase-lockedloopphasedetector.ThevoltageonisthesignalafterF/Vconversion.Ifthetonesignalisinputtothe②pin,thenthe⑤pinoutputstheFMsquarewavesignalmodulatedbythe②pininputsignal.FromthebasicfunctionofLM567,LM567canbeusedasanoscillator,modulatorordemodulator.Therefore,itcanbeusedasabasicdeviceinthecircuit.TheapplicationofLM567hasthefunctionofdecodingaspecificfrequencyintheinputsignal,anditiswidelyusedincommunication,remotecontrol,measurement,frequencymonitoring,etc.Figure3.LM567ToneDecoderIVTipsofUsingToneDecoderLM567AlthoughLM567hasaverywiderangeofapplications,ifitisnothandledproperlyduringdesignandapplication,itstillfailstoachievetheexpectedresults,andevenbringstroubletothedebuggingoraffectsthereliabilityoftheproduct.Therefore,itshouldbeconsideredfromthefollowingaspectswhenusingit:1.SetOperatingFrequencyandBandwidthofLM567AccuratelyandAppropriatelyWeknowthattheinternaloscillationfrequencyf0ofLM567canbepre-setwithintherangeof0.1KHzto500KHz,anditscorrespondingbandwidthcanalsobedeterminedasrequiredwithinthefieldrangeof7%f0to14%f0.Therefore,afterthedetectedsignalisdetermined,theinternaloscillationfrequencyf0ofLM567shouldbesettocoincidewiththecenterfrequencyofthemeasuredsignal,andthetimingcomponentsRandCconnectedwiththe5and6feetofLM567shouldbeusedwithhighprecision.Amongthem,thesettingofthecenterfrequencycanbedeterminedbytheresistancevalueofthetunerR.Whenadjusting,itisnecessarytopreventRshortcircuitoropencircuit,otherwisetheoutputlevelof⑧pinwillbelowlevelwhetherthereisinputsignalornot.Theexternalcapacitanceofthe②pinofLM567determinesthecapturebandwidth.Thesmallerthecapacity,thewiderthecapturebandwidth.However,thecapacitancecannotbereducedblindlytoincreasethebandwidth,soasnottoreducetheanti-interferenceabilityoreventriggerfalsely,whichaffectsthereliabilityoftheproduct.2.MaketheCenterFrequencyofthePassbandCoincidewiththeCenterFrequencyoftheOscillationAsMuchAsPossibleItshouldbenotedthatthecenterfrequencyofthepassbanddoesnotalwayscoincidewiththecenterfrequencyoftheoscillator,andsometimesitwilldeviateseverely.Thiswillinevitablycauseadecreaseinreliabilityandsensitivity.Therefore,measuresshouldbetakentomakethetwocenterscoincideasmuchaspossible.ThecircuitshowninFigure4canminimizethefrequencyoffsetofthetwocenters.Figure4.CircuitofLM5673.WorkingVoltageofLM567ShouldBeStableThestabilityoftheoperatingvoltageoftheLM567hasafixedresponsetothestabilityofthecenterfrequencyofthetonedecoder.4.AvoidMisoperationWhentheOutputTerminalisPoweredOnLM567outputsalowlevelatthemomentwhenthepoweristurnedon.Therefore,forsomeremotecontrolcircuits,itisnecessarytoaddaCRintegrationdelaycircuittotheoutputendtoavoiderroneousoperationwhenthepoweristurnedon.Thisisespeciallyimportantintheon-offcontrolcircuit.Afterreadingtheblog,haveyoubetterunderstandLM567?Finally,ifyouhaveanyquestionsaboutLM567,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!

STM32F769BIT6-208-LQFP-STMicroelectronics

IIntroductionWhentestingenvironmentalprotection,safety,andeconomicindicatorssuchasnoise,accelerationperformance,maximumspeed,andfuelconsumptionofmotorvehicles,itisnecessarytomeasureandcontrolthevehiclespeed.Mostexistingvehiclespeedmeasurementmethodsuseelectronictimingdevicesorstopwatchestomeasurevehicles.Thetimeittakestotravelafixeddistanceandthenfindtheaveragespeed.Generally,theprocessorandthedisplaypartoftheelectronictimingdevicearebasicallythesame,butthespeedsensorpartisdifferent,andthecharacteristicsofthesensordirectlyaffecttheaccuracyofthemeasurementresult.Atpresent,thecommonlyusedspeedsensorsincludepressuresensitivesensors,COMScamerasandparallellightsources.Theformerhasasimplestructure,butitiscumbersometolay,thesensoriseasilydamaged,andthesensitivityisreducedafterlong-termuse,whichaffectsthemeasurementresults.Thelatterhashighsensitivityandaccuratemeasurement.However,thecostistoohigh,involvesmoreequipment,andhashigherrequirementsfortheplacementofthelightsource.Consideringtheaboveproblems,itisafeasiblemethodtodesignanewinfraredspeedsensorusingLM567.Thesensorissmallinsize,lowincost,simpleinoperation,easytouse,hashighsensitivity,accuracy,stabilityandanti-interferenceability,andissuitableformeasuringtheaveragespeedofavehiclewithinafixeddrivingdistance.Figure1.LM567CatalogIIntroductionIIWorkingPrincipleofTraditionalSpeedMeasuringDevice2.1UsingPressureBeltRoadTester2.2UsingLaserRoadTesterIIIWorkingPrincipleofInfraredSpeedSensorBasedonLM5673.1InternalStructureandFunctionofLM5673.2PrincipleofInfraredSpeedMeasurementBasedonLM567IVConclusionOrdering&QuantityIIWorkingPrincipleofTraditionalSpeedMeasuringDeviceThefollowingusesthemeasurementofmotorcycleaccelerationnoiseasanexample,tointroducetheprinciplesandadvantagesdisadvantagesoftheconventionalspeedmeasuringdevicescurrentlycommonlyused.Figure1isasimplifiedlayoutofmotorcycleaccelerationnoisetest.2.1UsingPressureBeltRoadTesterForthespeedmeasurementmethodusingthepressurebeltroadtester,placethepressurebeltatAA,BB,CC,DDrespectivelyandstickthepressurebelttotheroadsurfacewell.ThedistancebetweenAAandBB,CCandDD(thatis,thespeedmeasurementzone)is1meter,andthepressurebeltandtheroadtesterareconnectedinsequencewithacable.WhenthevehiclepassesthepressurebeltatAA,thepressure-sensitivesensorinthepressurebeltistriggered,andthetriggersignalissenttotheroadtestertostartthetimingofitsinternaltimingdevice;WhenthevehiclepassesBB,atriggersignalisgeneratedagaintostopthetimingdevice.Usingtheinternalprocessoroftheroadtester,thetimetakentopassthedistancebetweenAAandBBisconvertedintovehiclespeedanddisplayedontheLCDscreen.Figure2.LayoutDiagramUsingPressureBeltRoadTesterSimilarly,avehiclespeedvaluecanbemeasuredbetweenCCandDDtomeettherequirementsofnoisemeasurement.Theworkingprincipleofthisspeedmeasurementmethodissimple,buttheequipmentismoretroublesometolay,andthesensoriseasilydamaged.Afterlong-termuse,thesensitivitywillbereduced,whichwillaffectthemeasurementresult.2.2UsingLaserRoadTesterForthespeedmeasurementmethodusingthelaserroadtester,fourparallellaserlightsourcesareplacedatfourpositionsofA,B,C,andD,andfourareplacedatfourpositionsofABCD.CMOScameraforreceivinglasersignals.Thelightsourcecanbeadjustedsothatthelaserlightemittedisalignedwiththecenterofthecamera,andthecameraisconnectedtotheroadtesterinsequence.WhenthevehiclepassesAA,thelightisblocked,andthecamerageneratesatriggersignaltomaketheinternaltimingdeviceoftheroadtesterwork;WhenthevehiclepassesBB,atriggersignalisgeneratedagaintostopthetimingdevice,andtheinternalprocessoroftheroadtesterisusedtoconvertthetimespentthroughthedistancebetweenAAandBBtothevehiclespeedanddisplayitontheLCDscreen.on.Figure3.LayoutDiagramUsingLaserRoadTesterSimilarly,aspeedvaluecanbemeasuredbetweenCCandDD.Thesensitivityandmeasurementaccuracyofthisspeedmeasurementmethodareveryhigh,buttheoperationisextremelyinconvenient.Notonlydoeseachlaserlightsourcerequireanindependentpowersupply,butalsothelasersignalmustbedirectedtothecenterreceivingpointofthecamera,whichplaceshighrequirementsontheplacementofthelightsource,otherwisethesensorwillbedifficulttoworkproperly.IIIWorkingPrincipleofInfraredSpeedSensorBasedonLM567Thisblogusesaphase-lockedloopaudiodecodingchipLM567todesignanewinfraredspeedsensor.Itscircuitdiagramandworkingprincipleareasfollows.3.1InternalStructureandFunctionofLM567LM567isspeciallyusedtodemodulateasingletonefrequencymodulationsignal,anditsoperatingfrequencycanbeashighas500kHz.Itiswidelyusedinindustrialautomaticcontrol,remotecontroltelemetry,securityalarmandotherfields.LM567ismainlycomposedofquadraturephasedetector,phase-lockedloopandamplifier.ItsinternalstructureisshowninFigure2.Pins5and6ofLM567areexternallyconnectedwithtimingresistorsandcapacitorsR,C.RandCdeterminethecenterfrequencyf0ofthephase-lockedloopinternalvoltagecontrolledoscillator,thatis,f0.ResistorRisconnectedbetweenpins5and6,ofwhichpin6isgroundedthroughcapacitorC(Uss).IfRis2~20k,theLM567canextractthetonesignalintherangeof0.01~500kHz.Pins1and2ofLM567arerespectivelyconnectedtothegroundwithacapacitortoformanoutputfilternetworkandaphase-lockedlooplow-passfilternetwork.ThecapacityoftheexternalcapacitorC2onpin2determinesthecapturebandwidthofthephase-lockedloop,anditssizeisBw1070.Uinistheeffectivevalueofthesinewavesignalvoltageinputfrompin3,andrequiresUin25mV,generallybetween100~200mV.TheexternalcapacitorC1ofpin1istheoutputfiltercapacitorofthequadraturephasedetector,anditscapacityismorethantwicethecapacityofthecapacitorC2connectedtopin2,whichshouldsatisfyC12C2.Figure4.TopViewofLM567(1)UsingLM567asFrequencyModulatorPin2isconnectedtotheinputofthelow-passfilterofthephase-lockedloop.Themodulatedsignaladdedfrompin2isfilteredbyalow-passfiltertoremoveout-of-bandnoiseandnoise,andthenaddedtothecenterfrequencyf0ofthevoltage-controlledoscillatorforfrequencymodulation,andthenthepin5outputstheFMsignal.Thecenterfrequencyf0oftheFMsignalisdeterminedbytheparametersoftheRCresistor-capacitornetworkconnectedtopins5and6.WhenLM567isusedasthefrequencymodulationcircuit,onlyitsinternalphase-lockedlooplow-passfilterandvoltage-controlledoscillatorareused.ChangingtheparametervalueoftheRCnetworkcanrealizemodulationtodifferentfrequencies.(2)UsingLM567asFrequencyDemodulatorThemodulatedsignalisinputfrompin3.Whenthecenterfrequencyoftheinputsignalisequaltothecenterfrequencyf0ofthevoltage-controlledoscillatorintheLM567,thelow-passfilter(pin2)oftheloopoutputsthedemodulatedsignal.3.2PrincipleofInfraredSpeedMeasurementBasedonLM567ThecircuitdiagramoftheinfraredspeedsensorbasedonLM567isshowninFigure3.TheinternaloscillatoroftheLM567providesasquarewavesignaltodrivefourLEDstoemitinfraredlight,anditsfrequencyisdeterminedbyR2andC4.Figure5.CircuitDiagramofInfraredSpeedSensorPlacethefoursensorsinthefourpositionsA,B,C,andDinFigure1.Whenthevehiclepassesthesensor,theinfraredraysemittedbytheLEDarereflectedbythevehiclebody.ThephotosensitivetubeQ1receivesthereflectedlight,isamplifiedbythetransistorandconvertedintoavoltagesignal,andissenttotheinternalphasedetectoroftheLM567forsynchronousdemodulation,andthenconvertedintoadigitalsignalbythecomparatorinsidetheLM567andoutputfrompin8.Theoutputsignalistransmittedtotheroadtester,whichtriggersthetimingdeviceintheroadtestertostarttiming.Similarly,whenthevehiclepassesthesensoratpointB,atriggersignalisgeneratedtostopthetimingdeviceandpasstheroadtester.TheinternalprocessoroperatestoobtainthespeedofthevehicleasitpassesAAandBB.LM567isaphase-lockedloopaudiodecodingcircuit.Inthecircuit,itisusedforfrequencyselection,thatis,thecircuitoutputslowlevelonlywhenthefrequencyofthe3-pininputsignalisconsistentwiththefrequencyoftheLM567internaloscillator,otherwisetheoutputishigh.Level.Inotherwords,onlywhenthereflectedinfraredlightreceivedbyQ1comesfromtheLEDinitsowncircuit,theLM567willoutputatriggersignalfromhightolowtotheroadtester.Thebiggestfeatureofthiscircuitistorealizetheautomaticsynchronizationoftheinfraredemissionfrequencyandtheworkingfrequencyofthereceivingcircuit;Thatis,thereisnospecialpulsegeneratingcircuitintheinfraredtransmittingpart,andthepulseisdirectlyintroducedfromthedetectioncircuitofthereceivingpart(LM567phase-lockedcenterfrequencysignal).Inthisway,thewiringanddebuggingworkissimplified,avoidinginconsistenttransmissionandreceptionfrequenciescausedbychangesinthesurroundingenvironmentandcomponentparameters,eliminatingmutualinterferencebetweenadjacentsensors,andgreatlyenhancingcircuitstabilityandanti-interferencecapabilities.IVConclusionTheinfraredspeedsensordesignedbasedontheLM567modulationanddemodulationfunctionrealizestheautomaticsynchronizationoftheinfraredtransmissionfrequencyandtheworkingfrequencyofthereceivingcircuit.Inaddition,ithasthecharacteristicsofstronganti-interferenceabilityandstability,lowcostandsimplestructure.Therefore,itcanbewidelyusedtomeasuretheaveragespeedofvehiclessuchasautomobilesandmotorcycles.Figure6.LM567Afterreadingtheblog,haveyoubetterunderstandLM567?Finally,ifyouhaveanyquestionsaboutLM567,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!TheLM2940isacommonlow-dropout(LDO)linearregulator.ThisisacomprehensiveintroductiontoLM2940voltageregulator,fromitspinout,feature,parametertoitsapplication,itsdifferencebetweenLM7805andmore.CatalogLM2940DescriptionLM2940PinoutLM2940FeaturesLM2940ParametersLM2940EquivalentLM2940VSLM7805LM2940TypicalApplicationLM2940PackageLM2940ApplicationComponentDatasheetLM2940DescriptionTheLM2940isacommonlow-dropout(LDO)linearregulator.Thedropoutvoltageofaregulatoristhevoltagerequiredbetweentheinputandtheregulatedoutputvoltage.Theregulatorwastesthisvoltage(multipliedbycurrent),sothelowerthedropoutonalinearregulator,themoreefficientitis.ThismeansthattheLM2940,witha5Vdropoutat1amp,canbeusedwitha6voltwallwarttoprovidearegulated5Voutput.Thisalsomeansthattheregulatorwilloperateatamuchlowertemperaturethanastandard7805,whichwouldrequireamuchhigherinputvoltage(around7.5volts)foraregulated5Voutput.LM2940PinoutLM2940voltageregulatorLM2940PinoutPinNo.PinNameDescription1VinA(+ve)voltageisgivenasinputtothispin.2GNDCommontobothInputandOutput.3VoutOutputregulated12VistakenatthispinoftheIC.LM2940FeaturesInputVoltageRange=6Vto26VDropoutVoltageTypically0.5VatIOUT=1AOutputCurrentinExcessof1AOutputVoltageTrimmedBeforeAssemblyReverseBatteryProtectionInternalShortCircuitCurrentLimitMirrorImageInsertionProtectionP+ProductEnhancementTestedLM2940ParametersOutputoptionsFixedOutputIout(Max)(A)1Vin(Max)(V)26Vin(Min)(V)6Vout(Max)(V)15Vout(Min)(V)5Fixedoutputoptions(V)5,8,9,10,12,15Noise(uVrms)150Iq(Typ)(mA)10ThermalresistanceJA(C/W)23Loadcapacitance(Min)(F)22RatingCatalogRegulatedoutputs(#)1Features-Accuracy(%)2PSRR@100KHz(dB)48Dropoutvoltage(Vdo)(Typ)(mV)500Operatingtemperaturerange(C)-40to125,-40to85LM2940EquivalentTheequivalentforLM2940isLM7805.LM2940VSLM7805TheLM7805isapopularlinearvoltageregulatorbecauseitrequiresnoadditionalcomponentstooperate.Itisaverylow-costcomponent.Becauseofitscharacteristics,itreducestheoutputvoltageattheexpenseofheatdissipation,makingitinefficient.TheLM7805requiresaminimuminputvoltageof7.3Vtofunctionproperly.Itcanhandleamaximumcurrentof1A.Somemodelscanhandleupto1.5A.Itisrecommended,andinsomecasesrequired,tousecapacitorstoreduceoreliminatetheeffectsofthefrequenciesintroducedbytheotherelementsofthecircuit.Theyalsohelptoreducetheimpactofpeakconsumption.WhiletheLM2940isfromadifferentgeneration,butitspinisstillcompatiblewiththeLM7805.ItisaLow-dropout(LDO)LinearRegulatorthatismoreefficientthantheLM7805,butitwillrequirecapacitors.ThemaindifferencebetweenLM2940andLM7805isthatthemaximumoutputcurrentofLM2940is1A.ThemaximumoutputcurrentofLM7805is1.5A.Othersareveryclose,soifthecircuitonlyrequires1Aorbelow,LM2940canbeusedinsteadofLM7805.Whatsmore,the7805isexpendingtheexcesspowerasheat.Whichisverylossyespecialyifyourprojectusesbatteries.Theotherchipisabuckconverterissoitapproaches90%efficiencybyswitchingsothereisnowasteheat,thatswhyeventhoughLM7805ischeaperandeasiertousebuttheresstillalotofpeoplewouldgoforLM2940.LM2940LM7805SchematicComparisonLM2940SchematicLM7805SchematicLM2940TypicalApplicationLM2940PackageLM2940ApplicationPostregulatorforswitchingsuppliesLogicpowerSuppliesIndustrialInstrumentationComponentDatasheetLM2940DatasheetIDescriptionThisblogusestheuniversalintegratedchipTL494toconvertanalogsignalsintoPWM(pulsewidthmodulation)signals.Intheoutputpart,N-channelMOSFETandP-channelMOSFETareusedtoformaswitchingpoweramplifier.CatalogIDescriptionIIIntroduction2.1SwitchingPowerAmplifierOverview2.2TL494IntroductionIIISchemeDesign3.1DutyCycleAdjustmentCircuit3.2InputSignalCompressionCircuit3.3MOSFETDriveCircuit3.4WorkingPrincipleofOutputPartIVExperimentalResultsVConclusionFAQOrdering&QuantityIIIntroduction2.1SwitchingPowerAmplifierOverviewWiththerapiddevelopmentofhigh-speedpowerMOSFETproductiontechnology,theoperatingfrequencyofMOSFETisgettinghigherandhigher,thedrivingmethodisgettingsaferandthepriceisgettinglower.Therefore,alargenumberofswitchingpoweramplifiersappliedtovarioushouseholdappliancesandindustrialalarmshaveappearedonthemarketinrecentyears.Comparedwiththelinearpoweramplifier,althoughthecircuitoftheswitchingpoweramplifierisslightlymorecomplicated.Butitisveryefficientandcanreducethesizeoftheheatsink,evenwithoutusingtheheatsink.Therefore,thevolumeoftheproductcanbegreatlyreduced.2.2TL494IntroductionTL494isaswitchingpowersupplypulsewidthmodulation(PWM)controlchip.Formanyyears,asthecheapestdouble-endedPWMchip,TL494hasbeenwidelyusedindouble-endedtopologiessuchaspush-pullandhalf-bridge.Becauseofitsloweroperatingfrequencyandsingle-endedoutputportcharacteristics.Itisoftenusedwithpowerbipolartransistors(BJT).IfusedwithpowerMOSFET,anexternalcircuitisrequired.TL494worksinawidevoltagerangefrom7Vto40V,withamaximumoperatingfrequencyof200kHz,withtheinternalsawtoothgenerator,PWMgenerator,andlagtimeadjustmentfunctions.IIISchemeDesignFigure1isablockdiagramofaTL494-basedswitchingpoweramplifier.Thekeytothecircuitdesignisthedutycycleadjustmentcircuit,inputsignalcompressioncircuit,andMOSFETdrivecircuit.Figure1.TL494SwitchingPowerAmplifier3.1DutyCycleAdjustmentCircuitThedutycycleisthekeytoimprovingvoltageutilizationduringPWMsignalmodulation.BecauseTL494isanintegratedchipforswitchingpowersupply.Therefore,theminimumlagtimeissetto0.1Vinternally.Themaximumdutycycleisapproximately96%attheoutputofthetransmitterstage.Figure2showstheinputpartandpartofthecircuitforPWMsignalmodulation.Figure2.SignalInputsectionandPWMGeneratorInFigure2,whenC4=1000pFandR4=24k,theoperatingfrequencyisabout78kHz.IfthereisnodutycycleadjustmentcircuitD8,D17,R23,becausethecomparisonpointoftheinternaldelaytimecomparatoris0.1V.Sotheminimumon-timeisabout1.52s,andtheminimumdutycycleisD=1.52/1312%.Therefore,thevoltageutilizationratewilldecreaseduringPWM.IfD8,D17,andR23areused,a0.82VbiasvoltagewillbegeneratedatthepointEofthecapacitorC4forthesawtoothwavegeneration,andthestartingpointofthesawtoothwavewillbeincreasedfrom0Vto0.82V.Therefore,theon-timeisreducedto0.64s,andtheminimumdutycycleisreducedtoD=0.64/134.9%.Thiscansignificantlyimprovethevoltageutilization.Figure3istheoutputwaveformwhenthereisnodutycycleadjustmentcircuit.Figure4istheoutputwaveformwhenthereisadutycycleadjustmentcircuit.Figure3.OutputWaveformwithoutDutyCycleAdjustmentCircuitFigure4.OutputWaveformwithDutyCycleAdjustmentCircuit3.2InputSignalCompressionCircuitBecausetheinputsignalofthealarmhasalargevariationrange,itisnecessarytocompressthesignalwithalargeamplitudeaccordingtoacertainratio.InFigure2,R6,R16,D10,D11constitutetheinputsignalcompressioncircuit,anditskeyistousetheinputcharacteristicsofthediode.Figure5showsitsinputcharacteristics.Amongthem,D10andD11areconnectedinparalleltocompresssignalsinbothpositiveandnegativedirections.Figure5.OutputCharacteristicsofInputSignalCompressionCircuitThecompressionratiodependsonthevaluesofR6andR16.Thelargerthevalue,thelargerthecompressionratio.ByadjustingthevaluesofR6andR16,thechangerangeofthecompressedsignalissetto-0.82V~0.82V.Theamountofchangeis1.64V.WecanseeFigure4,thesawtoothvoltagevariationrangeis0.82V~3.25V.SotheoutputsignalvariationrangeoftheTL494internalerroramplifieris2.43V.ThegainoftheinternalerroramplifierdependsonR7andR20.Byadjustingtheirvalues,whentheamountofchangeofthecompressedsignalis1.64V,theoutputsignalchangerangeoftheinternalerroramplifiercanbesetto2.43V.Sincemostalarmsusetweeters,thebasswithalargeamplitudecanbegreatlyreduced.3.3MOSFETDriveCircuitP-channelMOSFETusesIRF9540.Ithasthecharacteristicsofthemaximumoperatingvoltageof100V,themaximumoperatingcurrentof18A,andsaturationwhenVGSvoltageis5V~15V.N-channelMOSFETusesIRF540.Ithasthecharacteristicsofthemaximumoperatingvoltageof100V,themaximumoperatingcurrentof27A,andsaturationwhenVGSvoltageis5V~15V.ThedrivingtransistorQ3adoptsNPNtypeC8050,andQ7adoptsPNPtypeC8550.Bothofthesetwodrivetransistorshavethecharacteristicsofamaximumoperatingvoltageof30V,amaximumoperatingcurrentof1A,andaVBEof12V.Figure6showstheMOSFETdrivecircuit.Figure6.MOSFETDriveCircuitFigure7showstheMOSFETdrivingprinciplewaveform.WhenthepulsevoltageatpointAislow,thecurrentflowsthroughthereversebiasoftheZenerdiodeD7andthetransistorQ3toformaVGSvoltage,andQHisturnedon.WhenthepulsevoltageatpointAishigh,thecurrentflowsthroughthereversebiasoftheZenerdiodeD9andthetransistorQ7toformaVGSvoltage,andQListurnedon.Inaddition,Figure7alsoshowsdetaileddrivingwaveforms.lWhenthepulsevoltageislow,thevoltageislowerthanVLtomakeQHturnon.lWhenthepulsevoltageishigh,itsvoltageishigherthanVHtomakeQLturnon.IttakesacertainamountoftimetochangefromVLtoVH.Atthistime,QHandQLwillbecutoffatthesametime.Therefore,thepulsechangeprocessisverysafe.Figure7.MOSFETDrivingPrincipleWaveformTheVGSofQHandQLisdeterminedbythefollowingformula:Where:VGSisthedrivingvoltageofMOSFET;VCisthepowersupplyvoltage;VDistheregulatedvoltageofZenertubesD7andD9(usuallythesameZenertubeisused);VBEisthecounterbreakdownvoltageofC8050andC8550.Figure8isthemeasureddrivewaveform.Whenthepulsevoltagechangesfromlowtohigh,thetimeforQHandQLtocutoffatthesametimeisabout100~300ns.Figure8.MeasuredDriveWaveform3.4WorkingPrincipleofOutputPartAsshowninFigure6,theoutputpartconsistsofQH,QLandL3,C8,C5,andC7.TheoutputvoltageistransmittedtotheloadafterfilteringhighfrequencywavesthroughL3andC8.Generally,anelectrolyticcapacitorisusedattheoutputend,butthiscircuitusesC5andC7toformahalfbridge,andthenconnectthemidpointtotheload.Theadvantageofthisconnectionmethodisthatthetwocapacitorsarenotonlythetransmissionpathoftheoutputsignal(thecapacitancevalueistheparallelvalueofthetwocapacitors),butalsohasafilteringeffectonthepowersupply(thecapacitancevalueistheseriesvalueofthetwocapacitorsatthistime),andreducetheinternalpressureofthecapacitorbyhalf.IVExperimentalResultsTable1showsthequiescentcurrentwhentheinputvoltageis35Vandtheoperatingfrequencyis78kHzwhenusingdifferentvoltageregulatordiodes.ItcanbeseenfromTable1:Whenthevoltageregulationvalueofthevoltagestabilizingdiodeis0V,5V,thedistancebetweentheconductionpointsofVLandVHistooclose,andtheconductiontimeistoolong,andthereisalargerstaticcurrent.Althoughthecurrentisrelativelysmallat20V,theMOSFETgeneratessevereheat.AscanbeseenfromTable1,whentheoperatingvoltageis35V,theselectionrangeoftheZenerdiodeis7.5V~15V.VConclusionTheexperimentalresultsshowthatthePWMsignalofTL494isusedforN-channelMOSFETandP-channelMOSFETtoformaswitchingpoweramplifierwithauniquedrivingmodetoovercometheshortcomingsofsimultaneousconductionoftwopowerMOSFETs.Notonlythat,italsohasidealdrivewaveforms,efficiencygreaterthan95%,goodbandwidthandlowprice,whichfullymeetstherequirementsofindustrialalarms.Andunder18Woutputpower,comparedwiththepoweramplifiercomposedofTDA7481,thereisnotmuchdifference,andthereisbasicallynoheatingphenomenon,andtheheatsinkcanberemoved.Ifyouwanttogetmoreoutputpower,youonlyneedtoincreasetheworkingvoltagetomorethan35VandfitaproperZenerdiode.FAQWhatisTL494?TL494isaPWMcontrollerICusedforpowerelectronicscircuits.Itcomprisesofon-chiptwoerroramplifiersanoscillatorwithadjustablefrequencyfeature,anoutputflip-flophavingpulsesteeringcontrol,andanoutputcontrolcircuitwithfeedback.WhatisthedetaileddescriptionofTL494?TheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.WhatareTL494productfeatures?CompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeWhatisPWMIC?TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology....ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.HowdoesPWMICwork?Asitsnamesuggests,pulsewidthmodulationspeedcontrolworksbydrivingthemotorwithaseriesofON-OFFpulsesandvaryingthedutycycle,thefractionoftimethattheoutputvoltageisONcomparedtowhenitisOFF,ofthepulseswhilekeepingthefrequencyconstant.WhichICisbetterforabuckconverter,TL494orUC3843?TheymainlydifferintypeofcontrolTL494=voltagemodecontrol(Oneloopcontrol).whileUC3843usescurrentmodecontrol(Nestedloopcontrol,withainner/fastcurrentloopandanotherouter/slowervoltageloop)Typicallyvoltagemodeareusedinmultipleoutputconverterswithgoodcross-regulation.CurrentmodewhenyouwanttoparallelmultipleconverterstomakeasingleconverterwithhighercurrentratingTL494isaverypopularIC.IfyouhavesimplerequirementsTL494isrecommendedHowdoIproperlysetthefeedbackpinonaTL494SMPSIC?Thefeedbackpinistheoutputofbotherroramplifiers,usedincomparingandadjustingtheoutputpulsewidthtotheDCcontrolvoltage.OnvariouscircuitsIhavelookedup,theop-ampconnectedtopins23areusedtosetthegainofthefeedbackloop,using2resistorswithoneresistorconnectingto2.5Vpotentialdivideron5Vreferencevoltage.Withtheotherconnectingtotheoutput(viasuitableisolation)Thegainappearstobesetat101,usinga51kfeedbackwith510ohmstothe2.5Vreference.Itisusedtocontrolthegainofthefeedbackvoltage.NoliteratureIhaveyetfound,givesanindicationonhowthisgainbeset,exceptagraphshowinganopenloopgainof1000,presumablythegainissetforthebeststability,althoughtherewillalsobeatimeconstant.WhyistherenofrequencycompensationrequiredinTIsTL494examplebuckregulatordesign(operationalamplifier,buckphase,shiftphase,margin,TL494,electronics)?ItsafixedfrequencyPWMcontrollerwithinternaldeadtimetimer.Frequencycompensationisnotrequired.Takealookatthedatasheet.HowtouseTL494?

STM32F769BIT6-208-LQFP-STMicroelectronics

IDescriptionTL494,isaswitchingpowersupplypulse-widthmodulation(PWM)controlchip.DesignedandintroducedbyTexasInstrumentsintheearly1980s,theTL494gainedimmediateandwidespreadmarketacceptance,especiallyinATXhalf-bridgepowersuppliesforPCcomputers.TL494PWMControllerTL494hasbecomeanindustry-standardchip,producedbymanyintegratedcircuitmanufacturers.Widelyusedinsingle-endedforwarddual-tube,half-bridge,andfull-bridgeswitchingpowersupplies.TL494hastwopackagingforms,SO-16andPDIP-16,tomeettherequirementsofdifferentoccasions.CatalogIDescriptionIITL494FeaturesIIITL494InternalStructure3.15VReferenceSource3.2SawtoothOscillator3.3OperationalAmplifier3.4Comparator3.5PulseTrigger3.6QuietTimeComparatorIVTL494WorkingPrincipleVConclusionFAQOrdering&QuantityIITL494FeaturesCompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeInternalRegulatorProvidesaStable5-VReferenceSupplyWith5%ToleranceCircuitArchitectureAllowsEasySynchronizationIIITL494InternalStructureFigure1.TL494InternalStructure3.15VReferenceSourceTL494hasabuilt-inreferencesourcebasedonthebandgapprinciple.Thestableoutputvoltageofthereferencesourceis5V.TheconditionisthattheVCCvoltageisabove7V.Theerroriswithin100mV.Theoutputpinofthereferencesourceisthe14thpinREF.3.2SawtoothOscillatorTL494hasabuilt-inlinearsawtoothwaveoscillator,whichgeneratesa0.3~3Vsawtoothwave.TheoscillationfrequencycanbeadjustedbyanexternalresistorRtandacapacitorCt.Itsoscillationfrequencyis:f=1/Rt*CtAmongthem:TheunitofRtisohm;TheunitofCtisfarad.ThesawtoothwavecanbemeasuredattheCtpin.3.3OperationalAmplifierTL494integratestwooperationalamplifierspoweredbyasinglepowersupply.Thetransferfunctionoftheoperationalamplifierisft(ni,inv)=A(ni-inv),butitcannotexceedtheoutputswing.Ingeneralpowercircuits,theop-ampisconnectedtooperateinaclosed-loop.Open-loopisusedinafewspecialcases,andthesignalisinputfromtheoutside.Theoutputterminalsofthetwooperationalamplifiersarerespectivelyconnectedtoadiode,whichisconnectedtotheCOMPpinandthesubsequentcircuit(comparator).Thisensuresthatthehigheroutputofthetwoop-ampsentersthesubsequentcircuit.3.4ComparatorThesignal(COMPpin)outputbytheoperationalamplifierentersthepositiveinputterminalofthecomparatorinsidethechipandiscomparedwiththesawtoothwaveenteringthenegativeinputterminal.WhenthesawtoothwaveishigherthanthesignaloftheCOMPpin,thecomparatoroutputs0,otherwise,itoutputs1.3.5PulseTriggerThepulseflip-flopturnsonatthefallingedgeofthesawtoothwaveandthecomparatoroutputs1.Thismakesoneofthetwooutputs(inturn)on-chiptransistorsareturnedonandcutoffwhenthecomparatoroutputdropstozero.3.6QuietTimeComparatorThedeadzonetimeissetbyDeadTimeControlpin4.Itusesacomparatortointerferewiththepulsetriggerandlimitthemaximumdutycycle.Theupperlimitofthedutycycleofeachendcanbesetupto45%,andtheupperlimitofthedutycycleisabout42%whentheoperatingfrequencyishigherthan150KHz.(WhentheDTCpinlevelissetto0).IVTL494WorkingPrincipleTL494isafixedfrequencypulsewidthmodulationcircuitwithabuilt-inlinearsawtoothoscillator.Theoscillationfrequencycanbeadjustedbyanexternalresistorandacapacitor.Theoscillationfrequencyisasfollows:ThewidthoftheoutputpulseisachievedbycomparingthepositivesawtoothvoltageonthecapacitorCTwiththeothertwocontrolsignals.ThepoweroutputtubesQ1andQ2arecontrolledbyaNORgate.Itwillbestrobedwhentheclocksignaloftheflip-flopislow.Thatis,itwillbegatedonlywhenthesawtoothvoltageisgreaterthanthecontrolsignal.Whenthecontrolsignalincreases,theoutputpulsewidthwilldecrease.Wecantakealookatthepicturebelow.Figure2.TL494PulseControlWaveform​Thecontrolsignalisinputfromtheoutsideoftheintegratedcircuit.Oneissenttothedeadtimecomparator,andoneissenttotheinputoftheerroramplifier.Thedead-timecomparatorhasaninputcompensationvoltageof120mV,whichlimitstheminimumoutputdead-timetoapproximately4%ofthesawtoothperiod.Whentheoutputterminalisgrounded,themaximumoutputdutycycleis96%.Whentheoutputterminalisconnectedtothereferencelevel,thedutycycleis48%.Whenthedeadtimecontrolinputisconnectedtoafixedvoltage(rangebetween0-3.3V),additionaldeadtimecanbegeneratedontheoutputpulse.Thepulsewidthmodulationcomparatorprovidesameansfortheerroramplifiertoadjusttheoutputpulsewidth.Whenthefeedbackvoltagechangesfrom0.5Vto3.5,theoutputpulsewidthdropstozerofromthemaximumon-percentagetimedeterminedbythedeadzone.Thetwoerroramplifiershaveacommonmodeinputrangefrom-0.3Vto(Vcc-2.0),whichmaybedetectedfromtheoutputvoltageandcurrentofthepowersupply.Theoutputoftheerroramplifierisalwaysatahighlevel.ItperformsORoperationwiththeinvertinginputterminalofthepulsewidthmodulator.Itisthiscircuitstructurethattheamplifiercandominatethecontrolloopwithminimaloutput.WhenthecomparatorCTdischarges,apositivepulseappearsattheoutputofthedeadzonecomparator,andtheflip-flopconstrainedbythepulseistimed.AtthesametimestoptheworkoftheoutputtubesQ1andQ2.Iftheoutputcontrolterminalisconnectedtothereferencevoltagesource,themodulatedpulseisalternatelyoutputtothetwooutputtransistors,andtheoutputfrequencyisequaltohalfofthepulseoscillator.Ifitworksinasingle-endedstateandthemaximumdutycycleislessthan50%,theoutputdrivesignalisobtainedfromthetransistorQ1orQ2respectively.Afeedbackwindinganddiodeoftheoutputtransformerprovidefeedbackvoltage.Insingle-endedoperatingmode,whenahigherdrivecurrentoutputisrequired,Q1andQ2canalsobeusedinparallel.Atthistime,theoutputmodecontrolpinneedstobegroundedtoturnofftheflip-flop.Inthisstate,theoutputpulsefrequencywillbeequaltotheoscillatorfrequency.VConclusionThisblogsummarizesthecharacteristics,internalstructureandworkingprincipleofTL494.AlthoughthearchitectureofTL494hasbeenproventobeextremelyexcellentinhistory,itisfacingeliminationinthehigh-endmarketduetoitsoldtechnology,lowfrequency,andlackofnewenergy-savingfeatures.However,itisworthmentioningthatTL494isstillwidelyadoptedinthelow-endandmid-endmarkets.FAQWhatisTL494?TL494isaPWMcontrollerICusedforpowerelectronicscircuits.Itcomprisesofon-chiptwoerroramplifiersanoscillatorwithadjustablefrequencyfeature,anoutputflip-flophavingpulsesteeringcontrol,andanoutputcontrolcircuitwithfeedback.WhatisthedetaileddescriptionofTL494?TheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.WhatareTL494productfeatures?CompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeWhatisPWMIC?TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology....ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.HowdoesPWMICwork?Asitsnamesuggests,pulsewidthmodulationspeedcontrolworksbydrivingthemotorwithaseriesofON-OFFpulsesandvaryingthedutycycle,thefractionoftimethattheoutputvoltageisONcomparedtowhenitisOFF,ofthepulseswhilekeepingthefrequencyconstant.WhichICisbetterforabuckconverter,TL494orUC3843?TheymainlydifferintypeofcontrolTL494=voltagemodecontrol(Oneloopcontrol).whileUC3843usescurrentmodecontrol(Nestedloopcontrol,withainner/fastcurrentloopandanotherouter/slowervoltageloop)Typicallyvoltagemodeareusedinmultipleoutputconverterswithgoodcross-regulation.CurrentmodewhenyouwanttoparallelmultipleconverterstomakeasingleconverterwithhighercurrentratingTL494isaverypopularIC.IfyouhavesimplerequirementsTL494isrecommendedHowdoIproperlysetthefeedbackpinonaTL494SMPSIC?Thefeedbackpinistheoutputofbotherroramplifiers,usedincomparingandadjustingtheoutputpulsewidthtotheDCcontrolvoltage.OnvariouscircuitsIhavelookedup,theop-ampconnectedtopins23areusedtosetthegainofthefeedbackloop,using2resistorswithoneresistorconnectingto2.5Vpotentialdivideron5Vreferencevoltage.Withtheotherconnectingtotheoutput(viasuitableisolation)Thegainappearstobesetat101,usinga51kfeedbackwith510ohmstothe2.5Vreference.Itisusedtocontrolthegainofthefeedbackvoltage.NoliteratureIhaveyetfound,givesanindicationonhowthisgainbeset,exceptagraphshowinganopenloopgainof1000,presumablythegainissetforthebeststability,althoughtherewillalsobeatimeconstant.WhyistherenofrequencycompensationrequiredinTIsTL494examplebuckregulatordesign(operationalamplifier,buckphase,shiftphase,margin,TL494,electronics)?ItsafixedfrequencyPWMcontrollerwithinternaldeadtimetimer.Frequencycompensationisnotrequired.Takealookatthedatasheet.HowtouseTL494?IDescriptionThisblogintroducesapulsewidthmodulationtechnologywithTL494asthecontrolcore.AnditisappliedtoDCmotorcontrolsystem.Theworkingprincipleofthesystem,therealizationcircuitandthestructureandspecificapplicationofthePWMcontrolchipareanalyzedindetail.CatalogIDescriptionIIWorkingPrincipleandRealizationofControlSystem2.1HowSystemWorks2.2SelectionofPWMControlChip2.3RealizationCircuitofSystemIIISimulationResultsIVConclusionFAQOrdering&QuantityIIWorkingPrincipleandRealizationofControlSystem2.1HowSystemWorksThebasicdesignideaofthiscontrolsystemistouseastep-downchoppercircuitasshowninFigure1.Figure1.Step-downChopperCircuitanditsWaveformInthefigure,theDCpowersupplyisUd,andtheloadisamotor(M).Whentheswitchingdevice(VT)istriggeredandturnedon,theDCvoltageisappliedtothemotorforadurationoft1.Whenthefieldswitchingdeviceisturnedoff,thevoltageontheloadiszeroandlastsfort2time.IfwedefinethedutycycleT=t1+t2,andthedutycyclek=t/T,thewaveformdiagramandtheprincipleoftheDCchoppercircuitareasfollows:Theaveragevalue(Uo)ofthesystemoutputvoltageis:Theeffectivevalue(U)ofitsoutputvoltageis:Thepulsewidthmodulation(PWM)workingmodeadoptedbythissystemkeepsTunchangedandt1changes.TheprincipleblockdiagramofthecontrolsystemisshowninFigure2.Figure2.ControlSystemBlockDiagramThepowersupplyinthissystemmakesthemotorworkthroughthepowerdrivecircuit.Theon-offofthepowerdrivecircuitiscontrolledbythePWMcontrolchip.ThesystemsamplesthemotorcurrentfeedsitbacktothePWMcontrolchipandcomparesitwiththecurrentvalueofthecurrentcomparisoncircuit.TocontrolthePWMsignaloutputtoachievethepurposeofspeedregulation.ThesystemalsosamplesthepowersupplyvoltageandfeedsitbacktothePWMcontrolchip.Inthisway,itcanbecomparedwiththevoltagevalueofthevoltagecomparisoncircuittocontrolthePWMsignaloutputandachievetheeffectofUndervoltageprotection.WeusethecommonBUCKcircuitforthepowerdrivecircuitandPowerMOSFETfortheswitchtube.Theregulationofitsoutputvoltageisrealizedbycontrollingtheturn-ontimeofthedevice.Consideringtheinfluenceoftheinductanceofthemotor,theoutputcurrentisrelativelystableandtheenergyconsumptionislow.2.2SelectionofPWMControlChipInthecontrolcircuitofthemotorPWMcontrolsystem,theTL494chipisselected.TL494chiphasthefeaturesofstronganti-interferenceability,simplestructure,highreliabilityandlowprice.TheinternalcircuitofTL494(Figure3)consistsofthefollowingparts:Thereferencevoltagegeneratingcircuit;Oscillationcircuit;Intermittentadjustmentcircuit;Twoerroramplifiers;Pulsewidthmodulationcomparator;Outputcircuit;...Figure3.TL494InternalStructureAmongthem:Forpins1and2,theyarethenon-invertingandinvertinginputterminalsoferroramplifier1.Forpin3,itisphasecorrectionandgainscontrol.Forpin4,itisanintermittentperiodofconditioning,andthecut-offtimecanbechangedfrom2%to100%whenavoltageof0~3.3Visappliedtoit.Forpins5and6,theyareusedtoconnectexternaloscillationresistorRTandoscillationcapacitorCTtodeterminethefrequencyfoscofthesawtoothwavegeneratedbytheoscillator.Where:ThevaluerangeofRTandCT:RT=5~100kQ,CT=0.001~0.1F.Pin7isthegroundterminal;Forpins8,9and11,10,theyarethecollectorandemitterofthetwofinaloutputtransistorsinsideTL494;For12feet,itisthepowersupplyterminal;Forpin13,itistheoutputcontrolterminal.Whenthispinisgrounded,itisaparallelsingle-endedoutputmode.Whenpin14isconnected,itisapush-pulloutputmode;For14feet,itisthe5Vreferencevoltageoutputterminal,themaximumoutputcurrentis10mA;For15and16pins,theyaretheinvertingandnon-invertinginputterminalsoftheerroramplifier2.2.3RealizationCircuitofSystemTheconcreterealizationcircuitofthiscontrolsystemisshowninFig.4.Thesystemusescurrentnegativefeedbacktotrackthespeedofthemotor.Atthesametime,throughthenegativefeedbackofthevoltageofthepowersupply,thesystemhasthefunctionofundervoltageprotection.Figure4.SystemImplementationCircuitThemotorcurrentisdetectedandfedbacktopin1oftheerroramplifier1oftheTL494,comparedwiththecurrentreferencesignalofpin2tocontrolthePWMoutputofTL494.Soastorealizethefunctionofregulatingthespeedofthemotor.Byadjustingtheresistancevalueoftheadjustableresistor(RES1).Thatis,changethesizeofthesetcurrentreferencesignaltoadjustthedutycycleofthePWMoutputsignal.Soastoachievethepurposeofadjustingthemotorspeed.Bysamplingthevoltageofthepowersupply,itisfedbacktopin15oftheinternalerroramplifier2ofTI494.Thencomparewiththevoltagereferencesignalofpin16tocontrolthePWMoutputofTL494.Soastorealizetheundervoltageprotectionfunctionofthesystem.ThesystempowerisdrivenbyPowerMOSFET,whichhasahighinputimpedanceandcanbedirectlydrivenbyatransistor.Pin13ofTI494isusedtocontroltheoutputmode.Inthissystem,choosetoinputthisendaslowlevel.Atthistime,theflip-flopsQ1andQ2intheTL494donotwork,thetwooutputsarethesame,thefrequencyisthesameastheoscillatorfrequency,andthemaximumdutycycleis98%.IIISimulationResultsInordertoverifytheeffectivenessofthesystem,wecansimulatethecircuitoftheabove-mentionedDCmotorcontrolsystembasedonPWMtechnologybycomputer.WesetthesystemspowersupplyvoltageUcc=12V,DCmotorratedparameters:Un=12V,In=15A,4poles,armatureresistanceRa=0.21Q,momentofinertiaJ=0.57kg㎡.ThroughchangingtheadjustableresistanceRES1ofthecontrolcircuittorealizethedifferentdutyratioofthesystemoutput.Whentheoutputdutyratiois0.2,0.65/0.8,thevoltageandcurrentwaveformsofthemotorareshowninFigure5.Figure5.MotorVoltageandCurrentWaveformItcanbeseenfromFigure5thatwhenoutputtingdifferentdutyratios,thevoltageandcurrentwaveformsofthemotorarestable,whichisconducivetothelong-termstableoperationofthemotor.ThisshowsthattheTL494-basedPWMcontroltechnologyintroducedinthisarticleisfeasibleinpracticalapplicationsandrunsstably.IVConclusionThisblogsummarizesaPWMcontroltechnologybasedontheTL494chip.Thesimulationresultsshowthatthesystemhasasimplestructure,lowenergyconsumption,andstableoperation.AndthecharacteristicsoftheTL494chiphavebeenfullyutilizedsothatthesystemhastheadvantagesofundervoltageprotection.FAQWhatisTL494?TL494isaPWMcontrollerICusedforpowerelectronicscircuits.Itcomprisesofon-chiptwoerroramplifiersanoscillatorwithadjustablefrequencyfeature,anoutputflip-flophavingpulsesteeringcontrol,andanoutputcontrolcircuitwithfeedback.WhatisthedetaileddescriptionofTL494?TheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.WhatareTL494productfeatures?CompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeWhatisPWMIC?TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology....ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.HowdoesPWMICwork?Asitsnamesuggests,pulsewidthmodulationspeedcontrolworksbydrivingthemotorwithaseriesofON-OFFpulsesandvaryingthedutycycle,thefractionoftimethattheoutputvoltageisONcomparedtowhenitisOFF,ofthepulseswhilekeepingthefrequencyconstant.WhichICisbetterforabuckconverter,TL494orUC3843?TheymainlydifferintypeofcontrolTL494=voltagemodecontrol(Oneloopcontrol).whileUC3843usescurrentmodecontrol(Nestedloopcontrol,withainner/fastcurrentloopandanotherouter/slowervoltageloop)Typicallyvoltagemodeareusedinmultipleoutputconverterswithgoodcross-regulation.CurrentmodewhenyouwanttoparallelmultipleconverterstomakeasingleconverterwithhighercurrentratingTL494isaverypopularIC.IfyouhavesimplerequirementsTL494isrecommendedHowdoIproperlysetthefeedbackpinonaTL494SMPSIC?Thefeedbackpinistheoutputofbotherroramplifiers,usedincomparingandadjustingtheoutputpulsewidthtotheDCcontrolvoltage.OnvariouscircuitsIhavelookedup,theop-ampconnectedtopins23areusedtosetthegainofthefeedbackloop,using2resistorswithoneresistorconnectingto2.5Vpotentialdivideron5Vreferencevoltage.Withtheotherconnectingtotheoutput(viasuitableisolation)Thegainappearstobesetat101,usinga51kfeedbackwith510ohmstothe2.5Vreference.Itisusedtocontrolthegainofthefeedbackvoltage.NoliteratureIhaveyetfound,givesanindicationonhowthisgainbeset,exceptagraphshowinganopenloopgainof1000,presumablythegainissetforthebeststability,althoughtherewillalsobeatimeconstant.WhyistherenofrequencycompensationrequiredinTIsTL494examplebuckregulatordesign(operationalamplifier,buckphase,shiftphase,margin,TL494,electronics)?ItsafixedfrequencyPWMcontrollerwithinternaldeadtimetimer.Frequencycompensationisnotrequired.Takealookatthedatasheet.HowtouseTL494?

STM32F769BIT6-208-LQFP-STMicroelectronics

DescriptionTL494wasdesignedandlaunchedbyTexasInstrumentsintheearly1980s.Itwaswidelyacceptedbythemarketimmediatelyafteritwaslaunched,especiallyontheATXhalf-bridgepowersupplyofPCs.Untiltoday,aconsiderableproportionofPCpowersuppliesarestillbasedontheTL494chip.HowtoTestTL494NCatalogDescriptionComponentDatasheetTL494PinoutTL494ParameterFeaturesAdvantagesApplicationsTL494SimplifiedBlockDiagramTL494PackageandPinsFunctionalBlockDiagramWheretouseTL494HowtouseTL494TL494TypicalApplicationFAQOrdering&QuantityComponentDatasheetDatasheetTL494Pulse-Width-ModulationControlCircuitsdatasheet(Rev.H)Applicationnotes1IsolatedMultipleOutputFlybackConverterDesignUsingTL494Applicationnotes2DesigningSwitchingVoltageRegulatorsWiththeTL494(Rev.E)TL494PinoutPinDescriptionNameNO.1IN+1Noninvertinginputtoerroramplifier11IN2Invertinginputtoerroramplifier12IN+16Noninvertinginputtoerroramplifier22IN-15Invertinginputtoerroramplifier2C18CollectorterminalofBJToutput1C211CollectorterminalofBJToutput2CT5CapacitorterminalusedtosetoscillatorfrequencyDTC4Dead-timecontrolcomparatorinputE19EmitterterminalofBJToutput1E210EmitterterminalofBJToutput2FEEDBACK3InputpinforfeedbackGND7GroundOUTPUTCTRL13Selectssingle-ended/paralleloutputorpush-pulloperationREF145-VreferenceregulatoroutputRT6ResistorterminalusedtosetoscillatorfrequencyVCC12PositiveSupplyTL494ParameterTopologyBoost,Buck,Flyback,Forward,Full-Bridge,Half-Bridge,Push-PullControlmethodVoltageVCC(Min)(V)7VCC(Max)(V)40Dutycycle(Max)(%)45UVLOthresholdson/off(V)Frequency(Max)(kHz)300Operatingtemperaturerange(C)-40to85,0to70Gatedrive(Typ)(A)0.2FeaturesAdjustableSwitchingFrequency,DeadTimeControl,ErrorAmplifier,Multi-topologyRatingCatalogFeaturesCompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeInternalRegulatorProvidesaStable5-VReferenceSupplyWith5%ToleranceCircuitArchitectureAllowsEasySynchronizationAdvantagesTheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.TheTL494Cdeviceischaracterizedforoperationfrom0Cto70C.TheTL494Ideviceischaracterizedforoperationfrom40Cto85C.ApplicationsDesktopPCsMicrowaveOvensPowerSupplies:AC/DC,Isolated,WithPFC,90WServerPSUsSolarMicro-InvertersWashingMachines:Low-EndandHigh-EndE-BikesPowerSupplies:AC/DC,Isolated,NoPFC,90WPower:Telecom/ServerAC/DCSupplies:DualController:AnalogSmokeDetectorsSolarPowerInvertersTL494SimplifiedBlockDiagramTL494PackageandPinsPackagePinsSizePDIP(N)16181mm19.3x9.4SOIC(D)1659mm9.9x6SOP(NS)1680mm10.2x7.8TSSOP(PW)1622mm4.4x5FunctionalBlockDiagramWheretouseTL494TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology.TL494canbeusedtoprovideaconstantcurrentbyvaryingtheoutputvoltagetotheload.ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.SoifyouarelookingforanICtoproducePWMsignalsforcontrollingapowerswitchbasedonthecurrentflowingthroughthecircuit,thenthisICmightbetherightchoiceforyou.HowtouseTL494AtestcircuitfromtheTL494datasheetisshownbelow.NoninvertingpinsareconnectedtotheRefpinwhileinvertingpinsareconnectedtotheground.TestinputsaregiventoDTCandFEEDBACKpins.Externalcapacitorandresistorareconnectedtopin56tocontroltheoscillatorfrequency.Theerroramplifiercomparesasampleofthe5-VoutputtothereferenceandadjuststhePWMtomaintainaconstantoutputcurrentTL494TypicalApplicationSwitchingandControlSectionsInputPowerSourceError-AmplifierSectionCurrent-LimitingCircuitSoft-StartCircuitSwitchingCircuitPower-SwitchSectionFAQWhatisTL494?TL494isaPWMcontrollerICusedforpowerelectronicscircuits.Itcomprisesofon-chiptwoerroramplifiersanoscillatorwithadjustablefrequencyfeature,anoutputflip-flophavingpulsesteeringcontrol,andanoutputcontrolcircuitwithfeedback.WhatisthedetaileddescriptionofTL494?TheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.WhatareTL494productfeatures?CompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeWhatisPWMIC?TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology....ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.HowdoesPWMICwork?Asitsnamesuggests,pulsewidthmodulationspeedcontrolworksbydrivingthemotorwithaseriesofON-OFFpulsesandvaryingthedutycycle,thefractionoftimethattheoutputvoltageisONcomparedtowhenitisOFF,ofthepulseswhilekeepingthefrequencyconstant.WhichICisbetterforabuckconverter,TL494orUC3843?TheymainlydifferintypeofcontrolTL494=voltagemodecontrol(Oneloopcontrol).whileUC3843usescurrentmodecontrol(Nestedloopcontrol,withainner/fastcurrentloopandanotherouter/slowervoltageloop)Typicallyvoltagemodeareusedinmultipleoutputconverterswithgoodcross-regulation.CurrentmodewhenyouwanttoparallelmultipleconverterstomakeasingleconverterwithhighercurrentratingTL494isaverypopularIC.IfyouhavesimplerequirementsTL494isrecommendedHowdoIproperlysetthefeedbackpinonaTL494SMPSIC?Thefeedbackpinistheoutputofbotherroramplifiers,usedincomparingandadjustingtheoutputpulsewidthtotheDCcontrolvoltage.OnvariouscircuitsIhavelookedup,theop-ampconnectedtopins23areusedtosetthegainofthefeedbackloop,using2resistorswithoneresistorconnectingto2.5Vpotentialdivideron5Vreferencevoltage.Withtheotherconnectingtotheoutput(viasuitableisolation)Thegainappearstobesetat101,usinga51kfeedbackwith510ohmstothe2.5Vreference.Itisusedtocontrolthegainofthefeedbackvoltage.NoliteratureIhaveyetfound,givesanindicationonhowthisgainbeset,exceptagraphshowinganopenloopgainof1000,presumablythegainissetforthebeststability,althoughtherewillalsobeatimeconstant.WhyistherenofrequencycompensationrequiredinTIsTL494examplebuckregulatordesign(operationalamplifier,buckphase,shiftphase,margin,TL494,electronics)?ItsafixedfrequencyPWMcontrollerwithinternaldeadtimetimer.Frequencycompensationisnotrequired.Takealookatthedatasheet.HowtouseTL494?

I.DesriptionInthefieldofmeasurementandcontrol,itisoftenencounteredthattheoutputsignalofthemonitoredobjectissmall,anditisdifficulttodirectlycollectit.Generally,itneedstobeamplifiedbeforeprocessing.Thisarticleintroducesamethodofimplementingasmallsignalacquisitionsystem.Thesmallestsystemisrealizedbyusingthesingle-chipSTC25A60S2withA/Dconversionfunctionandtheeasy-to-useamplifierAD620withpreciseamplificationfunction.Thesystemdesignandimplementationarediscussedandtheacquisitionisintroducedindetail.Theprocessofsmallsignal,andgivespracticalapplicationexamples,aswellastheapplicationofsmallsignalacquisitioninrelatedfields.AD620CatalogI.DesriptionII.AD620IntroductionIII.IntroductiontoSTC12C5A60S2IV.SystemHardwareDesign4.1SystemPrincipleBlockDiagram4.2PowerSupplyCircuitDesign4.3SignalConditioningCircuit4.4SystemDecouplingCircuit4.5RealizationofA/DConversion4.6Follow-upWorkV.PracticalApplicationVI.ConclusionFAQOrdering&QuantityII.AD620IntroductionAsamonolithicinstrumentamplifier,AD620haslowpowerconsumption,achipwithhighgainthroughexternalresistors,andfeatureslowinputdriftandtemperaturedrift.AD620isdevelopedfromthetraditionalthreeoperationalamplifiers,butsomeofthemainperformanceisbetterthanthedesignoftheinstrumentamplifiercomposedofthreeoperationalamplifiers,suchaswidepowersupplyrange(2.3~18V),smalldesignvolume,andverypowerconsumptionLow(themaximumpowersupplycurrentisonly1.3mA),soitissuitableforlow-voltage,low-powerapplications.Figure1SchematicdiagramofAD620principleThemonolithicstructureandlasercrystaladjustmentofAD620allowcircuitcomponentstobecloselymatchedandtracked,therebyensuringtheinherenthighperformanceofthecircuit.AD620isathree-op-ampintegratedinstrumentationamplifierstructure.Inordertoprotectthehighprecisionofgaincontrol,theinputtransistorprovidesasimpledifferentialbipolarinput,andusestheprocesstoobtainalowerinputbiascurrent.Throughtheinputstageinternalop-ampThefeedbacktokeepthecollectorcurrentoftheinputtransistorconstant,andtheinputvoltageisaddedtotheexternalgaincontrolresistorRG.ThetwointernalgainresistorsofAD620are24.7k8,sothegainequationis:G=49.4k/RG+1(1)Fortherequiredgain,theexternalcontrolresistancevalueis:RG=49.4/(G-1)k(2)III.IntroductiontoSTC12C5A60S2STC12C5A60S2isanewgeneration8051single-chipmicrocomputerwithA/Dconversionfunction.Theinstructioncodeisfullycompatiblewiththetraditional8051,butthespeedis8-12timesfaster.With8channelsofhigh-speed10-bitinputA/Dconversion(250k/s),itcanbeusedfortemperaturedetection,batteryvoltagedetection,keyscanning,spectrumdetection,etc.TheusercansetanychannelasA/Dconversion,andtheportsthatdonotneedtobeusedasA/DcancontinuetobeusedasI/Oports.Itscharacteristicsareasfollows:Figure2STC12C5A60S2(1)On-chipintegrated1280bytesRAM;(2)WithEEPROMfunction(STC12C5A62S2/AD/PWMwithoutinternalEEPROM);(3)Enhanced8051CPU,1T,singleclock/machinecycle,instructioncodeisfullycompatiblewithtraditional8051;(4)InternalintegratedMAX810dedicatedresetcircuit(whentheexternalcrystalisbelow12M,theresetpincanbedirectlyconnectedtothegroundwith1Kresistance);(5)Userapplicationspace8K/16K/20K/32K/40K/48K/52K/60K/62Kbytes;(6)ISP(In-SystemProgrammable)/IAP(In-ApplicationProgrammable),noneedforadedicatedprogrammer,noneedforadedicatedemulator,youcandownloadtheuserprogramdirectlythroughtheserialport(P3.0/P3.1),andonepiececanbecompletedinafewseconds;(7)STC12C5A60S2serieshavedualserialports,onlythosewiththeS2logosuffixhavedualserialports,RxD2/P1.2(canbesettoP4.2byregister),TxD2/P1.3(canbesettoP4.3byregister);(8)GeneralI/Oports(36/40/44),afterreset,theyare:quasi-bidirectionalport/weakpull-up(normal8051traditionalI/Oport),whichcanbesettofourmodes:quasi-bidirectionalport/weakPull-up,push-pull/strongpull-up,onlyinput/highimpedance,open-drain,eachI/Oportdrivecapacitycanreach20mA,butthewholechipshouldnotexceed120mA;(9)A/Dconversion,10-bitprecisionADC,8channelsintotal,conversionspeedupto250K/S(250,000timespersecond),universalfull-duplexasynchronousserialport(UART),becausetheSTC12seriesishigh-speed8051,canreusetimerorPCAsoftwaretorealizemultipleserialports.IV.SystemHardwareDesign4.1SystemPrincipleBlockDiagramGenerallyspeaking,beforethesignalisused,itneedstobefilteredandthenamplified,oramplifiedandthenfiltered,andthenobtained/perceivedbymeanssuchasA/D.Forsmallsignals,thesignalamplitudeisonlyafewmillivoltsorevensmaller.Iffilteredfirst,usefulsignalsmaybefilteredout.Therefore,inthiscase,youneedtoamplifyfirst,thenfilter,andthenperformA/Dconversionorotherprocessing.Accordingtothecharacteristicsofthissystem,theinterferenceinthesystemcanbeignored,sothesignalfilteringlinkisnotconsidered.Therefore,thesystemismainlyrealizedthroughthreeimportantlinks:signalextraction,signalamplification,andA/Dacquisition.Thedatageneratedinthethirdlinkcanguidepeoplesworkordisplayrelevantinformation.TheblockdiagramoftheentiresystemisshowninFigure3.Figure3Systemblockdiagram4.2PowerSupplyCircuitDesignAD620amplifiercanusesinglepowersupplyordualpowersupply,butwhenusingdualpowersupply,itsperformanceisbetterthansinglepowersupply.Inintegratedcircuitdesign,singlepowersupplyiseasytoimplement,butconsideringtheworkingperformanceofthechip,dualpowersupplyisusedinthissystem.UsetheICL7660Schiptoconvertanexternalsinglepowersupplyintoadualpowersupply.ICL7660Sisavoltageconversionchipthatcanrealizethefunctionofconvertingapositivevoltagetoanegativevoltage,anditsperipheralcircuitisrelativelysimple.ThespecificcircuitisshowninFigure4.Figure4PowersupplyimplementationschematicdiagramTheotherchipsinthesystemarepoweredbyasingle5Vpowersupply,andtheconnected5Vpowersupplycanbeusedwithoutanyprocessing,whichisnotdescribedhere.4.3SignalConditioningCircuitTheactualweaksignalisgenerallymVlevelorevensmaller.Beforeprocessing,itneedstobeamplifiedandthenA/Dcollected.AccordingtotheA/DfunctionofSTC12C5A60S2,itisnecessarytoaccuratelyamplifythesignaltoreachtheVlevel,sotheAD620amplifierisused.AD620hasagoodamplificationeffecton2inputdifferentialsignals.Inpracticalapplications,thesignalsaregenerallygeneratedbyelectricbridges.Inordertorealizesignalamplification,AD620needsanexternalresistor,whichdeterminestheamplificationfactortogetherwiththeinternalresistor.SupposethemagnificationisG,thenthereisthefollowingformula.G=(RG/R1)+1(1)canalsobewrittenasthefollowingformula:G=49.4k/RG+1(2)1)Intheformula,RGistheinternalresistanceofAD620,andR1istheexternalresistance.Itcanbeseenfromtheformulas(1)and(2)thatthesizeofRGintheformula(1)is49.4k.Theconditionedsignalisoutputthroughthe6-pinofAD620.Atthistime,itcanbedirectlyconnectedtotheA/Dconversionchiptorealizedatacollection.Itcanbereducedbythecorrespondingmultiplewhenusingit.TheprincipleofsignalconditioningisshowninFigure5.Figure5Signalconditioningcircuit4.4SystemDecouplingCircuitSincethesystemmainlyrealizessmallsignalamplificationandA/Dconversionafteramplification,thechipthatcompletestheA/Dfunctionofthissystem,namelySTC12C5A60S2,usesitsownworkingpowersupplyasthereferencevoltage.Inordertoensuretheconsistencyoftheconversionresults,itisnecessarytoensurethepowersupplyvoltagestability.Tofilterouttheinterferenceinthepowersupply,itcanbefilteredbymultiplecapacitorsinparallel.Afterthecapacitorsareconnectedinparallel,thecapacitancevalueincreases,buttheequivalentresistanceinsidethecapacitorisreducedduetotheparallelconnection,whichisbeneficialtoreducetheloss.Therefore,manycapacitorsareusedinparallel,andtherealizationprincipleisshowninFigure6.Figure6Powerdecouplingcircuit4.5RealizationofA/DConversionAsmentionedearlier,STC12C5A60S2isasingle-chipmicrocomputerwithA/Dconversionfunction,whichisconvenient,simple,andmulti-functional.ItsA/Dconversiononlyrequires90clockcycles(relatedtoitsoperatingfrequency)atthefastest.ThissystemUseittoachieveA/Dconversion.STC12C5A60S2usesportP1asan8-channelA/Dconversioninputinterface.Whenusingit,youonlyneedtosetitasananaloginterface.Bysettingthecorrespondingregister,theA/Dconversioncanbecompleted.Theunusedpinscanstillbeusedasordinarytubes.ThissystemrealizestheA/Dconversionofoneinputsignal,soitonlyneedstosetone.Inthissystem,P1.0portisusedasthesignalinputport.ThissystemrealizestheprincipleofA/DconversionasshowninFigure7.Figure7A/Dacquisitioncircuit4.6Follow-upWorkAftertheA/Dconversioniscompleted,dataanalysisisrequired.Generally,itcanbesenttotheuppercomputerthroughthecommunicationport(usuallyserialport),andthedataisprocessedbytheuppercomputer.Accordingtothedifferentcharacteristicsofthespecificsystem,thedataprocessingmethodsarealsodifferent,soitsnoneedtodiscussthemindetailhere.Table1ADconversiondataandactualdataAfterthesystemperformsA/Dconversiononsignalsofdifferentsizes,aseriesofactualdataandtheoreticaldataareobtained,asshowninTable1.DrawthecurveofA/DdatathroughExcel,andfoundthatthesystemA/Dconverterhasgoodlinearity.AsshowninFigure8.Figure8LinearityofA/DconverterV.PracticalApplicationThesmallsignalconditioning,A/Dconversion,andprocessingmethodsarediscussedinmoredetailabove.Thespecificapplicationisintroducedbelowthroughexamples.Asakindofsensingelement,resistancestraingaugeiscommonlyusedtomonitorthedeformationoftheobject.Generally,thestraingaugeisattachedtothesidepointofthecomponent.Afterthecomponentisstressed,duetothestrainofthemeasuringpoint,theresistancechanges,resultinginaweakvoltagechange.Thevoltagechangecanbecalculatedtoobtainthedeformationdegreeofthecomponent,soastoachievethepurposeofmonitoringtheconditionofthecomponentandguidetherelevantengineeringpersonneltodealwithit.Thissystemcanbeappliedtothevoltagegeneratedbytheelectricbridge.AschematicdiagramoftheelectricbridgeisshowninFigure9.Inthefigure,R4,R3,R1,andR2arethefourarmsofthebridge,R4andR3arefixedresistancesofimpedance,andR1andR2areinOneisaresistorwhoseresistancevaluechangesafterbeingstressed.R4andR3havethesameresistancevalue,andR1andR2havethesameresistancevaluewhentheyarenotstressed.Inthecaseofnoforce,thetwopointsofthebridge3and4areequipotential,thatis,thepotentialdifferenceis0.IfitisinputasAD620,theinputsignalisconsideredtobe0,andthebridgeissaidtobebalancedatthistime.WhentheforceofR1orR2changes,theresultofthechangeisreflectedinitsresistancevalue,whichcanbeobtainedbyOhmslaw.Thepotentialatpoints3and4isdifferent,thatis,thereisapotentialdifference.Atthistime,thebridgeisoutofbalance,butatthistimeThesignalisveryweakandcannotbecollecteddirectly.Therefore,thesignalisamplifiedthroughthesignalconditioningcircuitmentionedinthearticle,thatis,points3and4inthebridgeareconnectedtopins2and3ofAD620,afteramplification,thenA/Dacquisitionisperformed.Figure9SchematicdiagramofelectricbridgeThissystemusesasimpleelectricbridgebuiltbyitselfduringsimulation,asshowninFigure10.Figure10SimpleelectricbridgeByadjustingR2inthefigure,differentweaksignalsaregenerated,andthesimplebridge1and2areconnectedtothesignalconditioningcircuit,andthenafterA/Dconversion,weaksignalacquisitioncanberealized.The1,2endsofthesimpleelectricbridgecorrespondtothe3and4endsinthefigure.Inthissimulation,adjustR2togenerateabout5.35mVatbothendsof1,2andadjusttheexternalresistanceinthesignalconditioningcircuitto160.7.Thecalculatedmagnificationisabout308.4times,andtheA/Dreferencevoltageis4.256VBymeasuringtheoutputofAD620,itcanbeobtainedthatthevoltageis1.645V,andthemagnificationfactorG=1.647V/5.35mV308canbecalculated.Itcanbeseenthatthemagnificationeffectisgood(afterremovingthemagnificationeffect,theerrorisonlynVlevel).ThroughmultipleA/Dconversions,thereturnedresultsareallaround0x018B,whichprovesthatthesystemhashighcredibility(ithasbeenusedinactualsystems).VI.ConclusionThisarticledescribesindetailthedesignandimplementationofsmallsignalacquisitionsystemsfromchipselection,circuitdesign,etc.,suchas8-bitsingle-chipSTC12C5A60S2asthecontrollerandA/Dconverter;AD620asthemainchipofthesignalconditioningcircuit;electricbridgeprincipleetc.Throughthetest,thecircuithasrealizeditsfunctionwell,andithasaccomplishedtheexpectedgoalexcellentlyintheactualsystem,whichhascertainpracticalvalue.FAQWhatisAD620?AD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyrequiresanexternalresistortosetthegain.Thegainrangeis1to10,000.CanIchangeAD620toAD623whenmakingMCUproducts?BothAD620andAD623aresingleinstrumentationamplifiers,andthepinarrangementisexactlythesame.Themaindifferenceis:AD620mustusepositiveandnegativepowersupplies,AD623canbeapositiveandnegativepowersupplyorasinglepowersupply.IftheoriginalboardisAD620,youcanreplaceitwith623;iftheoriginalboardisAD623,youmaynotbeabletoreplaceitwith620(itdependsonwhetherthepowersupplyoftheoriginalboardcircuitisdualpowersupplyorsinglepowersupply).AfterreplacingAD620andAD623insingle-chipproducts,theprogramcanworknormallywithoutmodification.WhatisthedifferencebetweenAD620BRandAD620AN?Theirpackagesaredifferent.WhatistheoutputresistanceofAD620?Howtoadjustit?AD620isakindoflowpowerconsumptioninstrumentamplifier,itsoutputresistanceisabout10K,thisistheinherentcharacteristicofthischip,generallyitisdifficulttoadjust.Ifyouhaverequirementsforoutputresistance,youcangenerallyuseanexternalcircuittosolveit.IsAD620apositivephaseamplificationorareversephaseamplification?AD620isaninstrumentamplifier,theoutputvoltageis[(Vin+)-(Vin-)]*gain.Ifthedesiredsignalis(Vin+)-(Vin-),thegainispositive,whichisequivalenttopositiveamplification.Conversely,ifthedesiredsignalis(Vin-)-(Vin+),thegainisequivalenttonegative,whichisequivalenttoreverseamplification.Whatisaninstrumentationamplifier?Instrumentationamplifier,animprovementofthedifferentialamplifier,hasaninputbuffer,doesnotrequireinputimpedancematching,sothattheamplifierissuitableformeasurementandelectronicinstrumentsDescriptionTIP122isanNPNDarlingtontransistor.Darlingtontransistormeanstherearetwotransistorinonepackageconnectedtoincreasegainatoutput.TIP122transistorhasalotofgoodfeatureslike5Acollectorcurrent,maxemitter-basevoltageis5V,maxcollectordissipationis65watt,minimummaximumcurrentgainisequalto1000.Thistransistorisdesignedtouseasaswitchandforamplificationpurposes.CatalogDescriptionTIP122ComponentDatasheetTIP122PinoutTIP122FeaturesTIP122ApplicationsTIP122EnvironmentalandExportClassificationsTIP122ParametersWorkingofTIP122HowtoSafelyLongRuninaCircuitDarlingtonCircuitSchematicWheretouseTIP122HowtouseTIP122TIP122ReplacementandEquivalentComplementofTIP122TIP122AlternativeNPNTransistorsTIP122SameFamilyTransistorsAdditionalResourcesFAQOrdering&QuantityTIP122ComponentDatasheetResourceTypeLinkDatasheetsTIP120-22TIP120-22,TIP125-27TO220B03PkgDrawingPCNObsolescence/EOLMultipleDevices19/Jun/2009MultDeviceEOL19/May/2017PCNDesign/SpecificationHeatsinkDesingChanges24/Feb/2014Logo17/Aug/2017PCNPackagingTapeandBox/ReelBarcodeUpdate07/Aug/2014MultDevices24/Oct/2017HTMLDatasheetTO220B03PkgDrawingTIP122PinoutPinNumberPinNameDescription1BaseItgovernsthebiasingofthetransistorandworkstoturnONorOFFthetransistor.2CollectorCurrentflowsinthroughcollector,usuallyconnectedtoload3EmitterCurrentcomesoutbytheemitter,itisusuallylinkedtoground.TIP122FeaturesHighDCCurrentGainhFE=2500(Typ)@IC=4.0AdcCollectorEmitterSustainingVoltage@100mAdcVCEO(sus)=60Vdc(Min)TIP120,TIP125=80Vdc(Min)TIP121,TIP126=100Vdc(Min)TIP122,TIP127LowCollectorEmitterSaturationVoltageVCE(sat)=2.0Vdc(Max)@IC=3.0Adc=4.0Vdc(Max)@IC=5.0AdcMonolithicConstructionwithBuiltInBaseEmitterShuntResistorsPbFreePackagesareAvailable*TIP122ApplicationsAudioAmplifierAudioAmplifierStagesAudioPreamplifiersSwitchingLoadsUnder5ATIP122EnvironmentalandExportClassificationsAttributeDescriptionRoHSStatusRoHSnon-compliantMoistureSensitivityLevel(MSL)1(Unlimited)TIP122ParametersBaseProductNumberTIP122CategoryDiscreteSemiconductorProducts-Transistors-Bipolar(BJT)-SingleCollector-BaseVoltageVCBO100VConfigurationSingleCurrent-Collector(Ic)(Max)5ACurrent-CollectorCutoff(Max)500ADCCurrentGain(hFE)(Min)@Ic,Vce1000@3A,3VDescriptionTRANSNPNDARL100V5ATO220ABDetailedDescriptionBipolar(BJT)TransistorEmitter-BaseVoltageVEBO5VFactoryPackQuantity200Height9.4mmLength10.67mmManufacturerONSemiconductorManufacturerProductNumberTIP122MaximumCollectorCut-offCurrent200uAMaximumDCCollectorCurrent5AMaximumOperatingTemperature+150CMinimumOperatingTemperature-65CMountingStyleThroughHoleMountingTypeThroughHoleOperatingTemperature-65C~150C(TJ)PackagingBulkPartStatusObsoletePower-Max2WProductTypeDarlingtonTransistorsSeriesTIP122SubcategoryTransistorsTransistorTypeNPN-DarlingtonUnitWeight0.042329ozVceSaturation(Max)@Ib,Ic4V@20mA,5AVoltage-CollectorEmitterBreakdown(Max)100VWidth4.83mmWorkingofTIP122Thistransistorisrecognizedforitshighercurrentgainwhichis1000andhighercollectorcurrent5amperes,therefore,itisusuallyusedtoswitchThistransistorhaslessbaseandemitterVoltageofthemerely5VhenceforthcanbeeffortlesslyorganizedbyaLogicinstrumentsuchasamicrocontrollerThoughprecautionhastobeengagedtocheck,ifthelogicinstrumentscanfontupto120mA.ThoughTIP122hasextraordinarycurrentatcollectorandcurrentgain,itisimpartiallymodesttoswitchtheexpedientmeanwhileithasanEmitter-Basevoltage(VBE)oftheonly5VandIbofmerely120mA.HowtoSafelyLongRuninaCircuitTogetbetterperformancewiththisdarlingtiontransistorwesuggesttoalwaysstayingbelowitsmaximumratings.Donotoperateitincircuitsusingmorethan100V.Donotprovideloadmorethan5A.Alwaysuseasuitablebaseresistortoproviderequiredcurrentatitsbase.Useasuitableheatsinktosaveitfromoverheatinganddostoreoruseitintemperaturebelow-65centigradeandabove+150centigrade.DarlingtonCircuitSchematicWheretouseTIP122Thistransistorisknownforitshighcurrentgain(hfe=1000)andhighcollectorcurrent(IC=5A)henceitisnormallyusedtocontrolloadswithhighcurrentorinapplicationswherehighamplificationisrequired.ThistransistorhasalowBase-EmitterVoltageoftheonly5VhencecanbeeasilycontrolledbyaLogicdevicelikemicrocontrollers.Althoughcarehastobetakentocheckifthelogicdevicecansourceupto120mA.So,ifyoulookingforatransistorthatcouldbeeasilycontrolledbyaLogicdevicetoswitchhighpowerloadsortoamplifyhighcurrentthenthisTransistormightbeanidealchoiceforyourapplication.HowtouseTIP122AlthoughTIPhashighcollectorcurrentandcurrentgain,itisfairlysimpletocontrolthedevicesinceithasanEmitter-Basevoltage(VBE)ofonly5Vandbasecurrentofonly120mA.InthebelowcircuitIhaveusedtheTIP122tocontrola48Vmotorwhichhasacontinuouscurrentofabout3A.Thecontinuescollectorcurrentofthistransistoris5Aandourloadconsumesonly3Awhichisfine.Themaximumbasecurrentisabout120mA,butIhaveusedhighvalueof100ohmresistortolimititto42mA.Youcanuseevena1Kresistorifyourcollectorcurrentrequirementisless.Thepeak(pulse)currentofthistransistoris8Asomakesureyourmotordoesnotconsumemorethanthat.Thisisjustamodelcircuitdiagramthatshowstheworkingonthistransistoritcannotbeusedassuch.So,similarlyyoucancontrolyourloadinthesameway.TIP122ReplacementandEquivalentTIP132,TIP102,NTE261,NTE263,2N6045,2N6045G,2SD2495,BDT65B,2N6532,BDT63B,BDW43,TIP142T(PinconfigurationofsometransistorsmaydifferfromTIP122,checkpinconfigurationbeforereplacinginacircuit)TIP22isadarlingtionpairtransistormanufacturedinTO-220package,itsagoodtransistortouseasahighgainswitchoramplifier.ComplementofTIP122ThecomplementoftheTIP122transistorisTIP127.TIP122AlternativeNPNTransistorsBC547,BC548,BC549,BC636,BC639,2N2369,2N3055,2N3904,2N3906,2SC5200TIP122SameFamilyTransistorsNPNFamilytransistorsareTIP120,TIP121,TIP122,andPNPFamilyareTIP125,TIP126,TIP127(PNP)AdditionalResourcesAttributeDescriptionOtherNamesTIP122FSTIP122FS-NDTIP122FS-NDRTIP122OSFAQWhatisTIP122transistor?TIP122TransistorisanNPNDarlingtontransistor....TIP122Darlingtontransistorhasalotofgoodfeatures,like5Acollectorcurrent,maximumemitter-basevoltageis5V,maximumcollectordissipationis65watt,andsoon.Thistransistorismanufacturedtouseasaswitchandforamplificationpurposes.WhattypeofpackageisusedforTIP122transistor?TheTIP122isasiliconNPNDarlingtontransistorinaTO-220typepackagedesignedforgeneralpurposeamplifierandlow-speedswitchingapplications.HowdoyoutestatransistorTIP122?Harvino.Theproperwaytotestistosetyourdmmtodiodetest(usually2ksettingontheohmscale).Transistorshavethreelegs;anemitter,abase,andacollector.HowdoIknowifmytransistorisblown?Connectthebaseterminalofthetransistortotheterminalmarkedpositive(usuallycolouredred)onthemultimeter.Connecttheterminalmarkednegativeorcommon(usuallycolouredblack)tothecollectorandmeasuretheresistance.Itshouldreadopencircuit(thereshouldbeadeflectionforaPNPtransistor).Whatarethe3terminalsofatransistor?Abipolartransistorhasterminalslabeledbase,collector,andemitter.Asmallcurrentatthebaseterminal(thatis,flowingbetweenthebaseandtheemitter)cancontrolorswitchamuchlargercurrentbetweenthecollectorandemitterterminals.HowtomakeminiaudioamplifieruseTIP122/TIP127transistor?

IntroductionLM339(Quaddifferentialcomparator)consistoffourindependentvoltagecomparators.Itisacommonintegratedcircuitandismainlyusedinhigh-voltagedigitallogicgatecircuits.UsingLM339caneasilyformvariousvoltagecomparatorcircuitsandoscillatorcircuits.CatalogIntroductionCatalogICircuitofSingleLimitComparatorIIOverheatDetectionandProtectionCircuitIIIHysteresisComparatorIVOver-voltageDetectionCircuitVDoubleLimitComparatorVIUsingLM339toformanOscillatorFAQOrdering&QuantityICircuitofSingleLimitComparatorFigure(a)showsabasicsinglelimitcomparator.AddtheinputsignalUIN(i.e.voltagetobecompared)tothein-phaseinputterminal,andconnectareferencevoltageUrattheanti-phaseinputterminal.WhentheinputvoltageUinUr,theoutputishighlevelUOH.Figure(b)showsitstransmissioncharacteristics.Figure1.CircuitofSingleLimitComparatorIIOverheatDetectionandProtectionCircuitItispoweredbyasinglepowersupply.Afixedreferencevoltageisaddedtotheanti-phaseinputterminalof1/4LM339,anditsvaluedependsonR1andR2.UR=R2/(R1+R2)*UCC.Thevoltageatthein-phaseterminalisequaltothevoltagedropofthethermistorRT.Whenthetemperatureinsidethemachineisbelowthesetvalue,the+terminalvoltageisgreaterthanthe-terminalvoltage,andUoisahighpotential.Whenthetemperaturerisesabovethesetvalue,the-terminalvoltageisgreaterthanthe+terminal,andtheUooutputisatzeropotential,whichcausestheprotectioncircuittooperate.AdjustingthevalueofR1canchangethethresholdvoltage,whichsetsthetemperaturevalue.Figure2.OverheatDetectionandProtectionCircuitIIIHysteresisComparatorThehysteresiscomparatorcanalsoberegardedasasinglelimitcomparatorwithpositivefeedback.Inthesinglelimitcomparatordescribedabove,iftheinputsignalUinhasslightinterferencenearthethreshold,theoutputvoltagewillproducecorrespondingundulation.Thisshortcomingcanbeovercomebyintroducingpositivefeedbackintothecircuit..Figure(a)showsahysteresiscomparator.ThefamiliarSchmidtcircuitisacomparatorwithhysteresis.Figure(b)showsthetransmissioncharacteristicsofthehysteresiscomparator.Figure3.HysteresisComparatorItisnotdifficulttoseethatoncetheoutputstateischanged,theoutputvoltagewillbestableaslongastheinterferencenearthejumpvoltagevaluedoesnotexceedthevalueofU.Accordingly,itcomestoareductioninresolution.Forthehysteresiscomparator,itcantdistinguishtwoinputvoltageswhosedifferenceislessthanU.Thehysteresiscomparatorwithpositivefeedbackcanacceleratetheresponsespeedofthecomparator,whichisoneofitsadvantages.Inaddition,sincethepositivefeedbackaddedbythehysteresiscomparatorisverystrongandmuchstrongerthantheparasiticcouplinginthecircuit,thehystericcomparatorcanalsoavoidtheself-oscillationcausedbytheparasiticcouplingofthecircuit.IVOver-voltageDetectionCircuitFigure4showsthepartofover-voltagedetectioncircuitinaninductioncookercircuit.Whenthegridvoltageisnormal,1/4lm339u42.8v,thecomparatorturnsover.Theoutputis0VandBG1iscutoff.ThevoltageofU5iscompletelydeterminedbythepartialvoltagevalueofR1andR2,whichis2.7V.ItmakesU4largerthanU5,whichmakesthestateafteroverturningextremelystableandavoidstheinstabilitycausedbythesmallfluctuationofgridvoltageneartheover-voltagepoint.Duetocertainhysteresis,afterovervoltageprotection,theinductioncookerstartstoworkagainwhenthegridvoltagedropsto242-5=237vandU4U3.Figure4.Over-voltageDetectionCircuitVDoubleLimitComparatorThecircuitinFigure5consistsoftwoLM339toformawindowcomparator.WhenthecomparedsignalvoltageUinisbetweenthethresholdvoltages(UR1UinUR2),theoutputishighpotential(UO=UOH).WhenUinisnotbetweenthethresholdpotentialrange,(UinUR2orUinUR1)theoutputislowpotential(UO=UOL),andthewindowvoltageU=UR2-UR1.Itcanbeusedtojudgewhethertheinputsignalpotentialisbetweenthespecifiedthresholdpotential.Figure5.DoubleLimitComparatorVIUsingLM339toformanOscillatorFigure6showsthecircuitofanaudiosquarewaveoscillatorcomposedof1/4LM339.ChangingC1canchangethefrequencyoftheoutputsquarewave.Inthiscircuit,whenC1=0.1uF,f=53Hz;whenC1=0.01uF,f=530Hz;whenC1=0.001uF,f=5300Hz.LM339canalsoformahigh-voltagedigitallogicgatecircuit,andcandirectlyinterfacewithTTLandCMOScircuits.Figure6.LM339OscillatorFAQWhatisLM339?LM339isavoltagecomparatorICfromLMx39xseriesandismanufacturedbymanyindustries.Thedevicesconsistoffourindependentvoltagecomparatorsthataredesignedtooperatefromasinglepowersupply.WhatisthedifferencebetweenLM324andLM339?TheLM324hasacomplementaryoutputwhiletheLM339isopencollector.Inthecomplementaryoutput,currentcanflowineitherdirectionasrequired(eithersourceorsink)whiletheopencollectoroutputcanonlysinkcurrent.HowdoesLM339comparatorwork?TheLM339isaquadopampcomparator.Acomparatorworksbyasimpleconcept.Eachopampofacomparatorhas2inputs,ainvertinginputandanoninvertinginput.Iftheinvertinginputvoltageisgreaterthanthenoninvertinginput,thentheoutputisdrawntoground.Whatiscomparatoric?Acomparatorisanelectroniccircuit,whichcomparesthetwoinputsthatareappliedtoitandproducesanoutput.Theoutputvalueofthecomparatorindicateswhichoftheinputsisgreaterorlesser.Pleasenotethatcomparatorfallsundernon-linearapplicationsofICs.WhatisthereplacementforLM339?LM311,LM324,LM397,LM139,LM239,LM2901Whatisacomparatorcircuit?Acomparatorcircuitcomparestwovoltagesandoutputseithera1(thevoltageattheplusside;VDDintheillustration)ora0(thevoltageatthenegativeside)toindicatewhichislarger.Comparatorsareoftenused,forexample,tocheckwhetheraninputhasreachedsomepredeterminedvalue.WhatistheuseofLM339?LM339isusedinapplicationswhereacomparisonbetweentwovoltagesignalsisrequired.Inadditionwithfourofthosecomparatorsonboardthedevicecancomparefourpairsofvoltagesignalsatatimewhichcomesinhandyinsomeapplications.IIntroductionInthisblog,wecomparetheLM339andLM339NproducedbyTI.Thecontentofcomparisonincludescomponentparameters,packaging,applicationareas,andtheircircuitdiagrams,etc.HopethisblogishelpfultothoseinterestedinLM339orLM339N.LM339NCatalogIIntroductionIIComponentDatasheetIIIDifferenceBetweenLM339andLM339NIVParametersVFeaturesVIApplicationsVIIPinoutFAQOrdering&QuantityIIComponentDatasheetComponentDatasheet1LM339NDatasheetComponentDatasheet2LM339DatasheetIIIDifferenceBetweenLM339andLM339N◾LM339Nisaquadvoltagecomparator.Itadoptsdualin-line14-pinpackage.Themaximumoperatingvoltageis18Vandthepowerconsumptionis265mW.Itisusedininductioncookersandotherproducts.◾LM339(Quaddifferentialcomparator)consistoffourindependentvoltagecomparators.Itisacommonintegratedcircuitandismainlyusedinhigh-voltagedigitallogicgatecircuits.LM339commonmoderangeisverylarge,from0vtothepowersupplyvoltage-1.5v;widesupplyvoltagerange:singlepowersupplyis2-36V;dualpowersupplyvoltageis1V~18V.IVParametersParametersLM339NLM339Numberofchannels(#)44OutputtypeOpen-collector,Open-drainOpen-collectorPropagationdelaytime(s)0.70.3Vs(Max)(V)3630Vs(Min)(V)22Vos(offsetvoltage@25C)(Max)(mV)55Iqperchannel(Typ)(mA)0.20.2Inputbiascurrent(+/-)(Max)(nA)25050Rail-to-railOutOutRatingCatalogCatalogOperatingtemperaturerange(C)0to700to70FeaturesStandardcomparatorStandardcomparatorVICR(Max)(V)3428.5VICR(Min)(V)00Approx.price(US$)1ku|0.241ku|0.05VFeaturesLM339NLM339WideSupplyVoltageRangeLM139/139ASeries2to36VDCor1to18VDCLM2901-N:2to36VDCor1to18VDCLM3302-N:2to28VDCor1to14VDCVeryLowSupplyCurrentDrain(0.8mA)IndependentofSupplyVoltageLowInputBiasingCurrent:25nALowInputOffsetCurrent:5nAOffsetVoltage:3mVInputCommon-ModeVoltageRangeIncludesGNDDifferentialInputVoltageRangeEqualtothePowerSupplyVoltageLowOutputSaturationVoltage:250mVat4mAOutputVoltageCompatibleWithTTL,DTL,ECL,MOS,andCMOSLogicSystemsWideSupplyRangesSingleSupply:2Vto36V(Testedto30VforNon-VDevicesand32VforV-SuffixDevices)DualSupplies:1Vto18V(Testedto15VforNon-VDevicesand16VforV-SuffixDevices)LowSupply-CurrentDrainIndependentofSupplyVoltage:0.8mA(Typical)LowInputBiasCurrent:25nA(Typical)LowInputOffsetCurrent:3nA(Typical)(LM139)LowInputOffsetVoltage:2mV(Typical)Common-ModeInputVoltageRangeIncludesGroundDifferentialInputVoltageRangeEqualtoMaximum-RatedSupplyVoltage:36VLowOutputSaturationVoltageOutputCompatibleWithTTL,MOS,andCMOSOnProductsComplianttoMIL-PRF-38535,AllParametersAreTestedUnlessOtherwiseNoted.OnAllOtherProducts,ProductionProcessingDoesNotNecessarilyIncludeTestingofAllParameters.VIApplicationsLM339NLM339High-PrecisionComparatorsReducedVOSDriftOvertemperatureEliminatesNeedforDualSuppliesAllowsSensingNearGNDCompatibleWithAllFormsofLogicPowerDrainSuitableforBatteryOperationIndustrialAutomotiveInfotainmentandClustersBodyControlModulesPowerSupervisionOscillatorsPeakDetectorsLogicVoltageTranslationVIIPinoutLM339andLM339NsharethesamepinoutdiagramFAQWhatisLM339?LM339isavoltagecomparatorICfromLMx39xseriesandismanufacturedbymanyindustries.Thedevicesconsistoffourindependentvoltagecomparatorsthataredesignedtooperatefromasinglepowersupply.WhatisthedifferencebetweenLM324andLM339?TheLM324hasacomplementaryoutputwhiletheLM339isopencollector.Inthecomplementaryoutput,currentcanflowineitherdirectionasrequired(eithersourceorsink)whiletheopencollectoroutputcanonlysinkcurrent.HowdoesLM339comparatorwork?TheLM339isaquadopampcomparator.Acomparatorworksbyasimpleconcept.Eachopampofacomparatorhas2inputs,ainvertinginputandanoninvertinginput.Iftheinvertinginputvoltageisgreaterthanthenoninvertinginput,thentheoutputisdrawntoground.Whatiscomparatoric?Acomparatorisanelectroniccircuit,whichcomparesthetwoinputsthatareappliedtoitandproducesanoutput.Theoutputvalueofthecomparatorindicateswhichoftheinputsisgreaterorlesser.Pleasenotethatcomparatorfallsundernon-linearapplicationsofICs.WhatisthereplacementforLM339?LM311,LM324,LM397,LM139,LM239,LM2901Whatisacomparatorcircuit?Acomparatorcircuitcomparestwovoltagesandoutputseithera1(thevoltageattheplusside;VDDintheillustration)ora0(thevoltageatthenegativeside)toindicatewhichislarger.Comparatorsareoftenused,forexample,tocheckwhetheraninputhasreachedsomepredeterminedvalue.WhatistheuseofLM339?LM339isusedinapplicationswhereacomparisonbetweentwovoltagesignalsisrequired.Inadditionwithfourofthosecomparatorsonboardthedevicecancomparefourpairsofvoltagesignalsatatimewhichcomesinhandyinsomeapplications.

IDescriptionThisblogmainlydiscussesandsolvesthefollowingproblem:HowtouseLM339voltagecomparatortomakeareservoirwaterlevelgauge?Accordingtowaterlevel,thisdesignperformssignalprocessingandcontrolsthepotentialofmultiplevoltagecomparators,sotheoutputwillchangeaccordingly.Therefore,underitsdrive,LEDcannotonlyemitlight,butalsoachievetheeffectofindicatingthewaterlevel.Figure1.LM339CatalogIDescriptionIIIntroductionIIIWokingPrincipleIVDeviceselectionandComponentProduction4.1deviceselection4.2PartProductionVInstallationandDebugging5.1DetectionPart5.2DisplayPartVIConclusionFAQOrdering&QuantityIIIntroductionDuetoinsufficientwatersupplyinsomeresidentialareas,pumpworkersmustfirststorewaterinthereservoirandthensupplywaterinaregularmanner.Inthisway,thepumpworkermustknowthewaterlevelofthereservoiratanytimeinthepumproom.Inthepast,electrodessuchascopperrodsorstainlesssteelwereusedtodetectthewaterlevelofthepool.However,duetoelectriccorrosion,thefunctionoftheelectrodeislostsoonafteruse.Forthisreason,thisblogusesLM339voltagecomparatortomakewaterlevelgauge.Thisnotonlyeliminatesthepainofoftenchangingelectrodes,butalsosimpleandeasy.Howsimpleisit?Onlytwowiresneedtobeconnectedfromthereservoirtothepumproom.Aftermorethantwoyearsofoperation,itsperformancehasbeenstableandreliable,achievingtheexpectedresults.IIIWokingPrincipleThemaincircuitofthewaterlevelgaugeiscomposedof4LM339voltagecomparators.Thiskindofintegratedcircuithasthecharacteristicsofeasypurchase,lowprice,singlepowersupplyoperationandwidedifferentialrange.EachLM339has4independentvoltagecomparators(15inthisdesign).Aslongasthepotentialdifferencebetweenthepositiveandnegativeinputterminalsis10mV,theoutputterminalcanbereliablyswitchedfromonestatetoanother.Whenthepositiveinputterminalis10mVhigherthanthenegativeinputterminal,itsoutputterminalishigh;Whenthenegativeinputis10mVhigherthanthepositiveinput,itsoutputislow.Inaddition,LEDscanbedrivendirectly.ThenhowtomaketheoutputendofLM339havehighandlowlevelchanges?Inspecificuse,anappropriateresistanceisgenerallyaddedbetweentheoutputterminalandthepositivepowersupply.Thisresistoriscalledapull-upresistor.Thatis,whentheoutputterminalofLM339isinahighimpedancestate,thepotentialoftheoutputterminalispulledupbytheresistor.Figure2.BlockDiagramofWaterLevelGaugeTheprincipleblockdiagramofthedeviceisshowninFigure2.Thevoltagesignalmeasurementconsistsofareedswitchandavoltagedividerresistor.Theringmagnetssuspendedinthewaterareindifferentpositions.Duetotheprincipleofelectromagneticinduction,notonlythecorrespondingdryreedswitchnormallyopencontactsareclosed,butalsothecorrespondingvoltagedividerresistorisconnected.Therefore,thecircuitwillpickupdifferentvoltagesignals.Thepotentialofthenegativeinputterminalofthecomparatorisformedbyafixedvoltagedividerresistor.Themeasuredvoltagesignaliscomparedwiththesetpotential.TheresultofthisisthattheLEDdisplaysthewaterlevelwhendriven.Inaddition,analarmisissuedwhenthehighestwaterlevelisreachedtoremindthepumpertostopwaterinjectiontopreventwateroverflow.TheconcretecircuitisshownasinFig.3.Figure3.WaterLevelGaugeCircuitDiagramInFigure3,thepowersupplyis+12V,andthedepthofthepoolisdividedinto15segmentsfordisplay.Inthispicture:A1~A15arevoltagecomparatorscomposedofLM339;GK1~GK15aredryreedswitches,thenormallyopencontactisclosedwhentheringmagnetisclosetoacertaindryreedswitch;ThevoltagedividercircuitcomposedofresistorsR1toR15determinesthepotentialofthepositiveinputterminalofeachcomparator.ThevoltageofthepositiveinputterminalofLM339changesduetothedifferentpositionsofthemagneticsteel.ThevoltagedividercircuitcomposedofresistorsR01~R030determinesthepotentialofthenegativeinputterminalofeachcomparator.Thepotentialofeachnegativeinputterminalisfixedafterdetermination.Whenthemagneticsteelfloatingonthewatersurfaceisclosetoacertaindryreedswitch,duetothepartialpressureofR1,R2,,R15,thepositiveinputterminalsofthecomparatorsA1,A2,,A15havedifferentinputs.Afterthissignaliscomparedwiththepotentialsetatthenegativeinputofthecomparator,therewillbeacorrespondingoutput.FromFigure3,whenGK1pullsin,itisequivalenttoholdingthemagneticsteelfloatattheupperlimitwaterlevel.Thepositiveinputofeachcomparatorisequaltothegroundpotential,whichislowerthantheirnegativeinput.Therefore,theoutputterminalsarealllowlevel,sothatallLEDsarelit.Atthistime,theoutputofA1dropsfromhighleveltolowlevel,andNE555istriggeredthroughcapacitorC.NE555isconnectedasamonostablecircuit.Oncetriggered,its3pinwilloutputahighlevel,whichwilldrivethebuzzertoalarm.ItsdurationisdeterminedbytheRCcomponentsconnectedtothe6and7pins.WhenGK2isclosed,LED2~LED15shouldbeonandLED1shouldbeoff.Atthistime,thepotentialofthepositiveinputterminalofeachcomparatorishigherthanthepotentialofthenegativeinputterminalofA1andlowerthanthepotentialofthenegativeinputterminalofA2~A15,andsoon.IVDeviceselectionandComponentProduction4.1deviceselectiona.SetthenegativeinputpotentialofeachcomparatortoVsh.Thenegativeinputpotentialofeachcomparatorissetartificiallyaccordingtothenumberofsegmentsdividedintopowersupplyandwaterdepth.Becausethepooldepthhasbeendividedinto15segmentsfordisplay,startingfrom2.0V,thedifferencebetweeneachadjacentnegativeinputterminalis0.4V.AsshowninthefirstrowinTable1.b.Selecttheresistancebetweenthenegativeinputterminalofeachcomparatorandthepowersupply,thatis,thevoltagedividerresistanceR01=R03==R029=20k,settoR.c.CalculatethegroundresistanceR02,R04,...,R030,whichisRr.SupposetheresistanceofthenegativeinputterminaltogroundisRr,andthepotentialofeachnegativeinputterminalisVsh,accordingtocircuitdiagram3:(1)Fromthisformula:(2)Forexample,tomakethepotentialofthenegativeinputterminalofthevoltagecomparatorA1Vsh=2V,accordingtoequation(2),wecangetAsshowninthesecondrowandthefirstcolumninTable1.TheselectionoftheotherresistorsR04,R06,,R030canbecalculatedaccordingtotheaboveformula(theresultisatheoreticalvalue,seethedatashowninthesecondrowinTable1fordetails).d.DeterminethenominalresistanceRbfromRr.Infact,thenominalvalueofcommerciallyavailableresistorsisdifferentfromthiscalculatedvalue.Inspecificapplications,anominalresistanceRbwithasimilarresistancevaluecanbeselected.ThespecificvalueisshowninthethirdrowofTable1.e.DeterminethepotentialVofthenegativeinputterminalofeachcomparatorAbyRb.WhenthenominalvalueofresistanceRbisselected,usethefollowingformulatocheckthepotentialVgeneratedbythisresistance.(3)Thespecificpotentialvalueisshowninthe4throwofTable1,comparedwiththesetvalueinthe1strow,aslongasitdoesnotexceed0.1V.f.DeterminetheresistancesR1,R2,,R15ofthepositiveinputterminalsofeachcomparatorandsetthemasRzh.FirstfindR1,setthepositiveinputpotentialofeachcomparatorasVzh,whenGK1pullsin,itcanbeseenfromTable1that2VVzh2.4V,setVzh=2.2V,R=20k,accordingtoformula(3),itcanbelistedThesolutionisthatRzh=R14.5k.Thisresistanceisnotthenominalvalue.Chooseasimilarnominalvalueof4.8k.ThenfindtheotherresistancesR2,R3,,R15,whichcanallbecalculatedbythismethod.Theresultisthetheoreticalvalue,whichhasaslightdeviationinpractice.Aftercorrection,thevalueisshowninthefifthrowofTable1.Aftertheaboveparametersareselectedinthisway,itcanbeensuredthatwhenthewaterlevelinthepoolreachesthelowestlimitandthefloatholdingthemagneticsteelsinkstothelowestposition,themagneticsteelseparatesfromallthereedswitchesandtheLEDsareallextinguished;AndwhenthefirstreedswitchGK1isclosed(equivalenttothewaterlevelinthepoolreachesthehighestlimit,thefloatholdingthemagneticsteelrisestothehighestposition)LEDsareallon.Whenthefloatisatacertainpositioninthemiddle,thecorrespondingLEDandtheLEDsbelowareallon,andtheLEDaboveitisoff,toshowthewaterlevel.Aftertheabovecalculation,thespecificdatashowninTable1isobtained.4.2PartProductionItisnecessarytomeasuretheheightfromthelowestwaterlevelofthereservoirtothelimitwaterlevel,anddividethisheightinto15segments.Thedistanceofeachsegmentislessthan200mm,thisdistancecanensurethatthemagneticsteelcanalwaysattractanadjacentdryreedswitch,soastoavoiddisplaybreakpoints.Thatistopreventthemagneticsteelfromnotattractingtheupperdryreedpipeorthelowerdryreedpipeduringoperation,sothattheLEDdisplayisallextinguished,causingtheillusionofwaterlessness.FortheconnectionsofGK1,R1~GK15,R15,firstsolderthemtoasmallprintedcircuitboardwithawidthlessthanorequalto20mm,andthenusewirestoconnectthematadistanceoflessthanorequalto200mm,andencapsulatethemina25mmhardplastictube..Theupperandlowermouthsofthepipeshouldbetightlysealedtopreventwaterleakage.Thetubeiscoveredwitharing-shapedmagnet.Afterdroppinganon-ferromagneticheavyobjectonthelowerendofthehardplasticpipe,theplasticpipeisverticallysunkintothebottomofthereservoir.Aringfloatisplacedunderthemagneticsteelandissleevedonthetube,andtheupperendofthetubeisfixedontheobservationportabovethereservoir.Duetothefunctionofthefloat,themagneticsteelisalwayssuspendedonthewatersurface,risingandfallingwiththewatersurface.Notethattheplaneofthemagneticsteelshouldalwaysbeparalleltothewatersurface,andtheplasticpipeshouldbeverticaltothewatersurfacetopreventthemagneticsteelfrombeingstuckbyfrictionwiththepipewallwhenthewaterlevelrisesandfalls.VInstallationandDebuggingThewholedeviceconsistsoftwoparts:Itisadetectionpartcomposedofareedswitchandvariousvoltagedividers;ItisthesignalprocessingdisplaypartcomposedofLM339.5.1DetectionPartBeforeencapsulatingtheplastictube,putsomesilicagelinthetubetoabsorbthemoistureinthetubeandpreventthelineinthetubefromgettingdamp.Ifring-shapedmagneticsteelisusedasthedetectionelement,thereedpipeconnectedinseriesintheplastictubeshouldberealizedbytwostaggeredreedpipes.Accordingtotheelectromagneticinductiontheory,theanalysisofthemagneticfieldlinesofthemagneticsteelshowsthatthereareasmallsectionofmagneticfieldlinesparalleltotheplaneofthemagneticsteelattheupperandloweropeningsofthemagneticsteel.Whenthissectionisclosetothereedswitch,thedirectionofitsmagneticfieldlineisperpendiculartothedirectionofthereedofthereedswitch.Atthistime,althoughthereedswitchisveryclosetothemagneticsteel,thecontactisstillreleasedanddisconnected,whichwillmakealltheLEDsgoout.Iftwostaggeredreedpipesareusedinstead,theproblemcanbesolved,andthestaggereddistancecanbedeterminedinexperiments.5.2DisplayPartThewaterlevelofeachsegmentisdisplayedbygreen10LED,andthelimitwaterlevelisdisplayedbyeye-catchingredLED.IftheLEDsarearrangedneatlytogether,thewaterlevelinthepoolcanbeclearlyseenaccordingtotheonoroffoftheLEDs.Equippedwithabuzzer,itwillgivethepumpworkeraclearerreminder.Note:Fromthedetectorinthepooltothecircuitboardofthepumproom,itisbesttouseshieldedwiretopreventinterferencesignalsfromentering.Weshouldalsonotethatthepowersupplymustberegulated.Fugure4.lm339VIConclusionThenegativeinputpotentialofthevoltagecomparatorA1~A15composedofLM339shouldbesetaccordingtoacertainrule,andthepotentialintervalbetweeneachotherdependsonthedepthofthecell.Ifthewaterlevelisdeeper,theintervalcanbesmaller,andthenumberofsectionscanbeselectedmore.Thepotentialdifferencebetweenadjacentcomparatorsisgenerally0.4V.Ifthepotentialdifferenceislarge,theselectionoftheresistanceiseasy;ifthepotentialdifferenceissmall,becausethenominalvalueintervalofthegeneralresistanceislarge,itisnecessarytouseanadjustableresistortoadjustthepotential.Ofcourse,inthecaseofsmallintervals,thesmallestpotentialdifferencebetweeneachothershouldbegreaterthan10mV,otherwisetheinputcharacteristicsofLM339willnotbeabletodistinguishthepotentialbetweeneachother.Inaddition,thevoltageofthepowersupplyandthenominalvalueofeachresistancemustbeconsidered.Thismethodcanalsobeappliedtootherfields.Suchasmonitoringthewaterdepthofrivers,rivers,lakes,andbays,theoillevelofgasstations,andthedepthofwatertanksinwaterplants.FAQWhatisLM339?LM339isavoltagecomparatorICfromLMx39xseriesandismanufacturedbymanyindustries.Thedevicesconsistoffourindependentvoltagecomparatorsthataredesignedtooperatefromasinglepowersupply.WhatisthedifferencebetweenLM324andLM339?TheLM324hasacomplementaryoutputwhiletheLM339isopencollector.Inthecomplementaryoutput,currentcanflowineitherdirectionasrequired(eithersourceorsink)whiletheopencollectoroutputcanonlysinkcurrent.HowdoesLM339comparatorwork?TheLM339isaquadopampcomparator.Acomparatorworksbyasimpleconcept.Eachopampofacomparatorhas2inputs,ainvertinginputandanoninvertinginput.Iftheinvertinginputvoltageisgreaterthanthenoninvertinginput,thentheoutputisdrawntoground.Whatiscomparatoric?Acomparatorisanelectroniccircuit,whichcomparesthetwoinputsthatareappliedtoitandproducesanoutput.Theoutputvalueofthecomparatorindicateswhichoftheinputsisgreaterorlesser.Pleasenotethatcomparatorfallsundernon-linearapplicationsofICs.WhatisthereplacementforLM339?LM311,LM324,LM397,LM139,LM239,LM2901Whatisacomparatorcircuit?Acomparatorcircuitcomparestwovoltagesandoutputseithera1(thevoltageattheplusside;VDDintheillustration)ora0(thevoltageatthenegativeside)toindicatewhichislarger.Comparatorsareoftenused,forexample,tocheckwhetheraninputhasreachedsomepredeterminedvalue.WhatistheuseofLM339?LM339isusedinapplicationswhereacomparisonbetweentwovoltagesignalsisrequired.Inadditionwithfourofthosecomparatorsonboardthedevicecancomparefourpairsofvoltagesignalsatatimewhichcomesinhandyinsomeapplications.I.IntroductionThe74HC595isan8-bitserial-inorparallel-outshiftregisterwithastorageregisterand3-stateoutputs.74HC595withthecharacteristicsofhighspeed,lowpowerconsumptionandsimpleoperation,canbeeasilyusedinMCUinterfacetodriveLEDoperation.ThisarticleintroducesthecircuitdesignofLEDdisplaydrivedby74HC595.CatalogI.IntroductionII.BasicDescription2.1LEDDisplay2.274HC595III.CircuitDesign3.1HardwareCircuit3.2DisplayDriverIV.ConclusionFAQOrdering&QuantityII.BasicDescription2.1LEDDisplayA7SegmentLEDDisplay,alsoknownasLEDdisplay,hasbeenwidelyusedinvariousinstrumentsbecauseofitslowprice,lowpowerconsumptionandreliableperformance.TherearemanytypesofLEDdriversonthemarket,andmostofthemhavemultiplefunctions,butthepriceiscorrespondinglyhigher.Ifusedinasimplesystemwithlowcost,itisnotonlyawasteofresources,butalsoincreasesthecostofproducts.Using74HC595chiptodriveLEDhasvariousdisadvantages.Highspeed,lowpowerconsumption,unlimitednumberofLEDs.ItcancontrolboththecommoncathodeLEDdisplayandthecommonanodeLEDdisplay.Thecircuitdesignedwith74HC595isnotonlysimple,butalsolowinpowerconsumptionandstrongindrivingability.Itisalowcostandflexibledesignscheme.2.274HC595The74HC595isan8-bitserial-in/serialorparallel-outshiftregisterwithastorageregisterand3-stateoutputs.Boththeshiftandstorageregisterhaveseparateclocks.Thedevicefeaturesaserialinput(DS)andaserialoutput(Q7S)toenablecascadingandanasynchronousresetMRinput.ALOWonMRwillresettheshiftregister.DataisshiftedontheLOW-to-HIGHtransitionsoftheSHCPinput.ThedataintheshiftregisteristransferredtothestorageregisteronaLOW-to-HIGHtransitionoftheSTCPinput.Ifbothclocksareconnectedtogether,theshiftregisterwillalwaysbeoneclockpulseaheadofthestorageregister.Datainthestorageregisterappearsattheoutputwhenevertheoutputenableinput(OE)isLOW.AHIGHonOEcausestheoutputstoassumeahigh-impedanceOFF-state.OperationoftheOEinputdoesnotaffectthestateoftheregisters.Inputsincludeclampdiodes.ThisenablestheuseofcurrentlimitingresistorstointerfaceinputstovoltagesinexcessofVCC.Figure1.74HC595FunctionalDiagramFigure2.74HC595LogicSymbolIII.CircuitDesign3.1HardwareCircuitFigure3isadisplaypanelcircuitdesignedwithAT89C2051and74HC595interface.Figure3.CircuitofDisplayPanelTheP115,P116,andP117oftheP1portareusedtocontrolthedisplayoftheLED,andtheyareconnectedtotheSLCK,SCLKandSDApinsrespectively.Threedigitaltubesareusedtodisplaythevoltagevalue.Onthecircuitboard,LED3isonthefarleftandLED1isonthefarright.Whensendingdata,firstsendthedisplaycodeofLED3,andfinallysendthedisplaycodeofLED1.ThebrightnessoftheLEDiscontrolledbytheresistanceofPR1toPR3.2.2DisplayDriverUseDISP1,DISP2,andDISP3tostoredisplaydata.AftertheCPUinitializationiscomplete,calltheLRDISPsubroutinetocleartheregisterof74HC595.ThereisnoneedtocalltheclearsubroutinebeforecallingthedisplaysubroutineDISPLAY.Nowwritethetwosubroutinesasfollows.①CLRDISP:MOVR2,#24CLRBIT:CLRSCLKCLRCMOVSDA,variable capacitor symbolCSETBSCLKDJNZR2,CLRBITRET②Display:CLRSLCKMOVR3,transistors testing#3MOVR0,#DISP3DISP1:MOVA,smd resistors codes@R0MOVR2,#8DISP2:CLRSCLKRLCAMOVSDA ,types of capacitorsCSETBSCLKDJNZR2,DISP2DECR0DJNZR3,decoupling capacitor valueDISP1SETBSLCKRETIV.ConclusionItcanbeseenfromtheaboveexamplesthattherearenocomplicatedtechnicalproblemsinthedesignofhardwareandsoftwarewhen74HC595isusedtodesignLEDdrivercircuit.Inaddition,74HC595canbeusednotonlytodriveLEDdisplays,butalsotodrivelight-emittingdiodes.Each74HC595candrive8LEDssimultaneously.Thissolutionisidealwhenthevolumerequirementsoftheproductarenothighandwanttoreducethecost.FAQWhatis74HC595?74HC595isashiftregisterwhichworksonSerialINParallelOUTprotocol.Itreceivesdataseriallyfromthemicrocontrollerandthensendsoutthisdatathroughparallelpins.Wecanincreaseouroutputpinsby8usingthesinglechip.Whatisa74hc595n?8-bitShiftRegister74HC595NAshiftregisterisachipyoucanusetocontrolmanyoutputs(8here)atthesametimewhileonlyusingafewpins(3here)ofyourArduino.Howdoesashiftregisterwork?Shiftregistersholdthedataintheirmemorywhichismovedorshiftedtotheirrequiredpositionsoneachclockpulse.Eachclockpulseshiftsthecontentsoftheregisteronebitpositiontoeithertheleftortheright.How74HC595ShiftRegiesterworks?The595hastworegisters(whichcanbethoughtofasmemorycontainers),eachwithjust8bitsofdata.ThefirstoneiscalledtheShiftRegister.TheShiftRegisterliesdeepwithintheICcircuits,quietlyacceptinginput.Howdoesan8bitshiftregisterwork?TheSN74HC595Nisasimple8-bitshiftregisterIC.Simplyput,thisshiftregisterisadevicethatallowsadditionalinputsoroutputstobeaddedtoamicrocontrollerbyconvertingdatabetweenparallelandserialformats.YourchosenmicroprocessorisabletocommunicatewiththeTheSN74HC595Nusingserialinformationthengathersoroutputsinformationinaparallel(multi-pin)format.Essentiallyittakes8bitsfromtheserialinputandthenoutputsthemto8pins.

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