4- to 20-mA Current Loop Transmitter Reference …

1 TPS7A1601 MSP430F5172J8J9S1D5, D6J6J5J7J2 BoosterPack InterfaceBoosterPack InterfaceJTAG InterfaceU1U3extintDAC161S997U220 LOOP +LOOP + VTIDA-006484- to 20-mA Current Loop Transmitter 4- to 20-mA LoopInterfaceLoop Input ProtectionJ1 TTTTI Designs4- to 20-mACurrentLoopTransmitterReferenceDesi gnDesignOverviewDesignFeaturesThe TIDA-00648TI Designis an industrystandard 4- to 20-mACurrent-LoopOutputSignal4- to 20-mAcurrentloop design 8- to 33-VInputallowsthe injectionof FSK-modulateddigitaldatainto 16-BitResolutionthe 4- to 20-mAcurrentloop for HART communication.

2 Loop-ErrorDetectionand ReportingExternalprotectioncircuitryis deployedin-placeforcompliancewith regulatoryIEC61000-4standards, ProgrammableOutput-CurrentErrorLevelsinc ludingEFT,ESD,and SimpleHARTM odulatorInterfacingcomplianceto IEC61000-4is necessaryto ensurethat ReverseInputand OvervoltageProtectionthe designnot only survives,but also performsasintendedin a harshand noisyindustrialenvironment. Designedto MeetIEC 61000 RequirementsDesignResourcesFeaturedAppli cations FactoryAutomationand ProcessControlToolFolderContainingDesign FilesTIDA-00648 Sensorsand FieldTransmittersActuatorControlDAC161S9 97 ProductFolderTPS7A1601 ProductFolder ActuatorControlMSP430F5172 ProductFolder BuildingAutomationTIDA-00459 ToolFolder PortableInstrumentationTIDA-00245 ToolFolderTIDA-00349 ToolFolderASKOur E2E ExpertsWEBENCH CalculatorTools1 TIDUAM6 October20154- to 20-mACurrentLoopTransmitterReferenceDesi gnSubmitDocumentationFeedbackCopyright

3 2015,TexasInstrumentsIncorporatedKey IMPORTANTNOTICEat the end of this TI referencedesignaddressesauthorizeduse, intellectualpropertymattersand otherimportantdisclaimersand SystemSpecificationsTable1. Key SystemSpecificationsPARAMETERSSPECIFICAT IONSANDFEATURESO utputsignalTwo-wire4- to 20-mAcurrentloop accordingto NAMURNE-43 Powersupplyvoltagerangeon loop interfaceterminals8 V to 33 VContinuousreverseinputvoltageUp to 33-VDCC ompliancevoltage8 VSupplycurrentconsumption< mA (to powerall the functionalblocksof the Transmitter ) (typical) (typical)ReversepolarityprotectionContin uousInputcurrentlimit<50 mASurgetransientImmunityDesignedto meetIEC 61000-4-5.

4 1-kVline-line(DM)Operatingtemperature 40 C to +85 CInterfaceconnectorTwo-pinTH terminalblock,6 A, mm for loop interface2 SystemDescriptionMonitoringand maintainingprocessvariablesat the appropriatelevelsis extremelycriticalin industrialautomationand sensorin the industrialenvironmentis eithercontinuouslyorperiodicallymeasurin gvital parameterssuchas temperature,pressure,flow,and so primarychallengeof sensingin industrialenvironmentsis conditioninglow signallevelsin the presenceof highnoiseand industrialprocesscontrolinstruments,anal og4- to 20-mAcurrentloopsare commonlyusedfor analogsignaling,with 4 mA representingthe lowestend of the rangeand 20 mAthe key advantagesof the currentloop are that the accuracyof the signalis not affectedbyvoltagedropin the interconnectingwiringand the loop can supplythe operatingpowerto the significantelectricalresistanceexistsin the line, the currentloop transmittermaintainsthe propercurrent,up to its usedto measurepressure,temperature,level,flow,p H.

5 Or a 4- to 20-mAcurrentloop can also be usedto controla valvepositioneror TIDA-00648referencedesigncomesin a TI BoosterPack Plug-inModuleto extendthe functionalityof the designsTI LaunchPad DevelopmentKits and add a 4- to designfilesincludeschematics,bill of materials(BOM),layerplots,Altiumfiles,Ge rberFiles,and the TI MSP430 to 20-mACurrentLoopTransmitterReferenceDesi gnTIDUAM6 October2015 SubmitDocumentationFeedbackCopyright 2015,TexasInstrumentsIncorporatedTPS7A16 01 MSP430F5172J8J9S1D5, D6J6J5J7J2 BoosterPack InterfaceBoosterPack InterfaceJTAG InterfaceU1U3extintDAC161S997U220 LOOP +LOOP + VTIDA-006484- to 20-mA Current Loop Transmitter 4- to 20-mA LoopInterfaceLoop Input TIDA-00648 SystemBlockDiagramThe goal of this referencedesignis to focuson the designof a two-wire.

6 Loop-powered4- to 20-mAcurrentloop transmitterthat is robust,low-power,precise,and stablein the boardcomesina BoosterPackformfactorand has the followingadditionalfeatures: Loopinputprotection:This featureprotectsthe designagainstdifferentialinputsurgepulse s(accordingto EN 61000-4-5,upto 1 kV, 42 ), as well as againstreverseinputvoltage(or the reverseconnectionof the nominalinputvoltageby miswiring).Surgepulsesare clampedby an onboardtransient-voltage-suppression(TVS )diodeto a safe voltagelevelbelow60 V. Reverseinputvoltagecan be completecircuitryfunctionsevenunderrever seinputvoltageconditions,but the accuracyandotherperformanceparametersexp eriencedegradation.

7 Currentlimiterand circuitryto protectthe currentsensecircuitryinsidea loop-poweredtransmitter:Eachsuddenincrea seof the loop inputvoltagecausesa suddenpulsecurrentthroughthe inputcapacitorof the exampleof a suddenincreaseof the inputvoltageat the loop inputterminalsoccursduringthe initialpower-upor loop currentis sensedand controlledby the respective4- to 20-mADACin a connectedtransmittercircuit,this pulsecurrentflowsthroughthe sensitivecurrentshuntinsidethis maximumcurrentratingfor the currentthroughthis currentshuntexists,whichrequireslimiting the currentbelow50 mAin the caseof a simple200- resistorand a dedicatedactivecurrentsourcehavebeenimpl ementedfor this October20154- to 20-mACurrentLoopTransmitterReferenceDesi gnSubmitDocumentationFeedbackCopyright 2015,TexasInstrumentsIncorporatedCOMABAS EOUTC2 SCLKC3 SDIC1 VDERRLVLCSBVACOMD40 HARTM odulatorLDO4- to 20-mALoopS P I80kIDAC " DAC16 DAC161S997 LOOP+LOOP ERRB+ TIDA-00648referencedesignfeaturesthe followingdevices.

8 DAC161S997 16-bitSPI-programmableDACfor 4- to 20-mAloops MSP430F5172 MSP430F51x2ultra-low-powermixed-signalMC U TPS7A1601 60-V,5- A IQ, 100-mA,low-dropoutvoltageregulatorFor moreinformationon eachof thesedevices,see the respectiveproductfoldersat DAC161S997is a very-low-power,16-bit DACfor transmittingan analogoutputcurrentoveranindustrystandar d4- to DAC161S997has a simplefour-wireSPI for datatransferand configurationof the reducepowerand componentcountin compactloop-poweredapplications,the DAC161S997containsan internalultralow-powervoltagereferencean d an low powerconsumptionof the DAC161S997resultsin additionalcurrentbeingavailableforthe remainingportionof the loop driveof the DAC161S997interfacesto a HART modulator.

9 Allowingthe injectionof FSK-modulateddigitaldatainto the 4- to combinationofspecificationsand featuresmakesthe DAC161S997idealfor two- and DAC161S997is availablein a 16-pin4-mm 4-mmWQFN packageand is specifiedovertheextendedindustrialtemper aturerangeof 40 C to +105 DAC161S997 BlockDiagramSomeof the highlightedfeaturesof the DAC161S997are: 16-bitresolution Verylow supplycurrentof 100 A 5 ppmFS/ C gain error Pin-programmablepower-upcondition Loop-errordetectionand reporting44- to 20-mACurrentLoopTransmitterReferenceDesi gnTIDUAM6 October2015 SubmitDocumentationFeedbackCopyright 2015,TexasInstrumentsIncorporated0100200 30040050060070080090010000 Output Current (mA)VDROP(mV) 40 C+ 25 C+ 85 C+ 105 C+ 125 Programmableoutput-currenterrorlevels SimpleHART modulatorinterfacing Highlyintegratedfeatureset in smallfootprintWQFN-16(4- 4-mm, )

10 Wideinputrangeis oftenrequiredin industrialenvironmentsto protectlargetransientsfromdamagingthe wide-inputratingrelaxesthe designof externalprotectioncircuitryand minimizesprotectioncircuitrycost and a wide-inputrangesafelyregulatethe output-powersupplyrail at V, evenwhenencounteringhigh voltagetransientsat the voltagetransientscausehigh heat;therefore,a properpackagemustbe selectedto LDOwith lowquiescentcurrentis the best choicefor a 4- to requiredto controlinternalcircuitrythat use of a FET as an internalpassdevicesupportsthe ultralow5 A of quiescentcurrentand a dropoutvoltagescalingthat is almostlinearwith the outputcurrentof the LDO(seeFigure4).