LM1949 Injector Drive Controller (Rev. C) - TI.com

1 FEB1995 REVISEDMARCH2013LM1949 InjectorDriveControllerCheckforSamples:L M19491 FEATURESDESCRIPTIONTheLM1949linearintegr atedcircuitservesasan2 LowVoltageSupply(3V )excellentcontroloffuelinjectordrivecirc uitryin AdaptabletoAllInjectorCurrentLevelscurre ntrequiredtoopena solenoidisseveraltimes HighlyAccurateOperationgreaterthanthecur rentnecessarytomerelyholdit TTL/CMOSC ompatibleInputLogicLevelsopen;therefore, theLM1949,bydirectlysensingtheactualsole noidcurrent,initiallysaturatesthedriver ShortCircuitProtectionuntilthe peak injectorcurrentisfourtimesthatof HighImpedanceInputtheidleor holding current(Figure19 Figure22).

2 ExternallySetHoldingCurrent, thenautomaticallyreducedtothesufficienth olding InternallySetPeakCurrent(4 IH) , ExternallySetTime-Outthetotalpowerconsum edbythesystemis ,ahigherdegreeof AvailableinPlastic8-PinPDIP correlationoffueltotheinputvoltagepulse( ordutycycle)isachieved, 5V 10%supply,theICis FuelInjectiontypicallyoperableovertheent iretemperaturerange ThrottleBodyInjection( 55 C to+125 C ambient)withsuppliesaslowas3 coldcrank AirandFluidValvesconditionswhenthebatter yvoltagemaydroplowenoughtoderegulatethe5 -voltpowersupply.

3 DCMotorDrivesTheLM1949is availableintheplasticPDIP,(contactfactor yforotherpackageoptions). ,standardwarranty,andusein 1995 2013, FEB1995 (1)(2)SupplyVoltage8 VPowerDissipation(3)1235mWInputVoltageRa nge 40 C to+125 CStorageTemperatureRange 65 C to+150 CJunctionTemperature150 CLeadTemp.(Soldering10sec.)260 C(1)AbsoluteMaximumRatingsindicatelimits beyondwhichdamagetothedevicemayoccur.(2) If Military/Aerospacespecifieddevicesarereq uired,pleasecontacttheTexasInstrumentsSa lesOffice/Distributorsforavailabilityand specifications.

4 (3)Foroperationin ambienttemperaturesabove25 C,thedevicemustbederatedbasedona 150 C maximumjunctiontemperatureandathermalres istanceof100 (VCC= ,VIN= ,TJ= 25 C,Figure1, unlessotherwisespecified.)SymbolParamete rConditionsMinTypMaxUnitsICCS upplyCurrentOffVIN= 0V1123mAPeakPin8 = 0V2854mAHoldPin8 Open1626mAVOHI nputOnLevelVCC= 253+25 AIOPO utputCurrentPeakPin8 = 0V 10 22mAHoldPin8 Open 5mAVSO utputSaturationVoltage10mA,VIN= ,tt RTCT90100110%2 SubmitDocumentationFeedbackCopyright 1995 2013, FEB1995 1995 2013,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback3 ProductFolderLinks.

5 LM1949LM1949 SNLS349C FEB1995 (continued) 1995 2013, FEB1995 REVISEDMARCH2013 TypicalPerformanceCharacteristics(contin ued) 1995 2013,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback5 ProductFolderLinks:LM1949LM1949 SNLS349C FEB1995 controlorientedprocessor(COPS ), microprocessor, ,in theformofa squarewavewitha variabledutycycleand/orvariablefrequency ,is typicalsystem,inputfrequencyis ,theengineexhaustismonitoredandtheair-to -fuelmixtureisvaried(viathedutycycle)tom aintaina perfect,orstochiometric, a ,it is necessarytobeabletodesigna modelfora , , ,if pronouncedenough,canbeavaluableaidin determiningthecurrentnecessarytoopena inductancemanifestsitselfasa breakpointin ,thecurrentnecessarytoovercometheconstri ctiveforcesofthatparticularinjectoris TypicalFuelInjector6 SubmitDocumentationFeedbackCopyright 1995 2013, FEB1995 REVISEDMARCH2013 PEAKANDHOLDCURRENTST hepeakandholdcurrentsaredeterminedbythev alueofthesenseresistorRS.

6 ThedriverIC,wheninitiatedbya logic1 signalatPin1, ratedependentuponL1, R1, ,andwhenthisdropreachesthepeakthresholdl evel,typically385mV,theICis closedloopsystemtomaintaintheholdreferen cevoltage,typically94mV,acrossRS. Oncetheinjectorcurrentdropsfromthepeakle veltotheholdlevel,it preferablewhenworkingwithsolenoids,since thecurrentrequiredtoovercomekineticandco nstrictionforcesisoftena ,powerdissipationin thesolenoidsandQ1is , it ,a peakcurrentofapproximately4 . , ,IRdropswithinthecomponentleadsorprinted circuitboardmaycreatesubstantialerrorsun lessappropriatecareis (Pins4 and5 respectively),shouldbeKelvinconnectedtoR S.

7 (withoutplated-throughholes) ,whenthebatteryvoltageis lowduetoenginecranking,orjustundercharge d, ,theinjectorcurrentcanbeseentobeleveling outat3 amps,or1 ampsmayoverheattheinjectors,thetimerfunc tionontheICwillforcethetransitionintothe holdstateafteronetimeconstant(thetimecon stantis equaltoRTx CT), orwhenthevoltageontheTIMERpin(Pin8)isgre aterthantypicallyVSUPPLYx 63%. notneeded,it canbedisabledbygroundingtheTIMERPin(Pin8 ).Forsystemswheretheinitialpeakstateisno trequired,( ,wherethesolenoidcurrentrisesimmediately totheholdlevel), donebysettingthetimeconstantequaltozero, ( ,CT= 0).

8 LeavingRTin placeis Figure1. However,theactualusefulrangeofthetimerex tendsfrommicrosecondstoseconds, reset(discharged)whentheINpin(Pin1)is belowtheVOL(MIN) (VBE) bydischargingit witha ,a F capis resetin approximately25 (fromPin2 toPin3) , F workwellwiththecircuitofFigure1. F (disc)providesa closeoptimuminchoicebetweeneconomy,speed , , F ,however, 1995 2013,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback7 ProductFolderLinks:LM1949LM1949 SNLS349C FEB1995 inductive,a voltagespikeis producedatthecollectorofQ1anytimetheinje ctoris ,(whenthecurrentis reducedtoonefourthofitspeakvalue),andals oattheendofeachinputpulse,(whenthecurren tisreducedtozero).

9 Thezenerprovidesa currentpathfortheinductivekickback, ,theratedzenervoltageatthesystempeakcurr entmustbelessthantheminimumbreakdownofQ1 . Also,evenwhileZ1isconductingthemajorityo ftheinjectorcurrentduringthepeak-to-hold transition(seeFigure20), ,asdescribedin thefollowingtext,canbecorrectedif theICdemands94mVacrossRS, ,thesafeoperatingarea(SOA)ofQ1mustinclud etheholdcurrentwitha notdesired,thezeneranodemaybereconnected tothetopofRSasshowninFigure21. Sincethevoltageacrossthesenseresistornow accuratelyportraystheinjectorcurrentatal ltimes, usuallyonlymillisecondslong,Q1couldsuffe rpermanentdamageunlessbufferedbytheinjec torandZ1.

10 Thereis onereasonwhya zeneris preferredovera clampdiodebacktothebatteryline, 1995 2013, FEB1995 Figure1 is dependentuponseveralexternalfactors, , ,ina typicalcycleofoperation, usuallymuchlongerthanthepeakstate,andint hepeakstatenearlyallpoweris storedasenergyinthemagneticfieldoftheinj ector, lessaccurateinthecaseoflowbatteryvoltage ,it Typicalvaluesaregivenin parentheses:RS= SenseResistor(0,1 )VH= SenseInputHoldVoltage(.094V)VP= SenseInputPeakVoltage(.385V)VZ= Z1 ZenerBreakdownVoltage(33V)VBATT= BatteryVoltage(14V)L1= InjectorInductance(.)