USB PD Power Negotiations - Texas Instruments

1 1 SLVA842 November2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedUSBPD PowerNegotiationsApplicationReportSLVA84 2 November2016 USBPD PowerNegotiationsABSTRACTThis documentdescribesthe PowerDelivery(PD)contractnegotiationin USBType-Cconnectionsper theUSB-IFPD specification,and its implementationusingTexasInstrumentsTPS65 982 USBType-CandUSBPD is requiredin USBType-Csystemsfor powerlevelsabove15 W (5 V at 3 A)up to 100 W (20 V at 5 A) accordingto the digitalcommunicationbetweenthe transmitterand receiverendsof a connectionsupportUSBPD, the flow ofUSBPD powernegotiation,as wellas the procedurefor implementinganddebuggingUSBPD negotiationsusingthe TPS65982deviceand TPS65982deviceis referredto throughoutthis applicationreport,but the documentalso appliestothe TPS65981and TPS65986 USBType-Cand USBPD Sinkand Specificationfor Specificationfor SinkCapabilities(PDOs).

2 Specificationfor Sinkand TraceAnalysisof Sinkand SourceCapabilitiesand SinkCapabilitiesto NegotiatePowerBasedon SystemInformationto PDO1 AcceptedWithno PDO3 AcceptedWithCapabilityMismatch= Rx SinkCapabilitiesRegister(0x31)Readsall Zeros(0)..19 List of Figures1Tx Traceof Tx Traceof Traceof SuccessfulPD StatusRegisterReadfromTPS65982 Actingas SourceCapabilitiesRegisterReadfromTPS659 82 Actingas SinkCapabilitiesRegisterReadfromTPS65982 Actingas November2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedUSBPD PowerNegotiations13 NewSet of Five SinkPDOsin Replyto GSkCPD SinkafterSSrCCommandis : PDO1 AcceptedWithno : PDO3 AcceptedWithCapabilityMismatch= : Rx SinkCapabilitiesRegister(0x31)Readsall Zeros(0)..1921 FailureType3 trademarksare the propertyof November2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedUSBPD PowerNegotiations1 IntroductionThe USBP owerDelivery(PD)Specificationdescribesa standardnegotiationprocessfor establishingallPD USBType-Cstandardallowsfor providing5 V at up to 15 W of Power ,followingthe PD protocolis criticalfor offeringor receivingany voltagehigherthan5 V.

3 As a result,anyproductthat requiresor deliverspowerfrom5 to 20 V (15 to 100 W of Power )mustnegotiateaccordingtoa specificset of TPS65982deviceis the USBType-Cand PD port controllerwith the highestlevelof integrationavailableon the TPS65982devicecan automaticallydetecta Type-Cport connection,negotiatea PD contract,and controla set of integratedpowerswitcheswithoutthe involvementof anyotherICs in the firmware(FW)of the TPS65982device,is configurable,any source,sink,or dual-roleport (DRP)productpossiblecan be createdon top of the core-firmwarebaseof theTPS65982device,whichis compliantto the USBPD coreFW also preventsproblematicsituationswith noncompliantproductsand recoversfromPD messagingerrorswith a chapterincludesthe following: A reviewof the rulesand flow of powernegotiationfollowingthe USBPD Specification Stepsto set up and modifyexamplesof PD sink and sourcecapabilitiesusedby the TPS65982 FWthroughoutthe negotiationprocess Stepsto verifythe correctpowernegotiationflow with the following.

4 Understandingthe powernegotiationflow of the USBPD Specification Analyzingthe resultsof the PD powernegotiationin real-timeusingdecodedPD tracesthatcapturethe communicationbetweentwo products Stepsto modifythe sourceand sink capabilitiesof the TPS65982deviceinstantlyusingthe hostinterface Stepsto debugcommonissuesand achievea successfulPD powernegotiation2 USBP owerDeliverySpecificationfor Sinkand SourceCapabilitiesThe USBPD Specificationexplicitlydescribesthe formatof datathat will be sent betweenthe sourceandsink duringa meaningof eachbit in the specificationis notalwaysnecessary,the PD-relatedregisters(receivedand transmitted)and PD analyzersof the devicefollowthe specificationexactlyand thesesimilaritiesare integratedin this sourcemustorganizethe capabilitiesof the powersupplyinto a list of Power -dataobjects(PDOs).Table1. GenericPDOBitsValueParameter31-3000bFixe dsupply01bBattery10bVariablesupply11bRes erved29-0 Specificpowercapabilitiesare describedby the PDOsin the Sinkand November2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedUSBPD PowerNegotiationsTable2.

5 Fixed-SupplyPDO SourceBitsParameter31-30 Fixedsupply29 Dual-rolepower28 USBsuspendsupported27 Externallypowered26 USBcommunicationscapable25 Dual-roledata24-22 Reserved Shallbe set to zero21-20 Peakcurrent19-10 Voltagein 50-mVunits9-0 Maximumcurrentin 10-mAunitsTable3. Variable-Supply(Nonbattery)PDO SourceBitsParameter31-30 Variablesupply(nonbattery)29-20 Maximumvoltagein 50-mVunits19-10 Minimumvoltagein 50-mVunits9-0 Maximumcurrentin 10-mAunitsTable4. Battery-SupplyPDO SourceBitsParameter31-30 Battery29-20 Maximumvoltagein 50-mVunits19-10 Minimumvoltagein 50-mVunits9-0 Maximumallowablepowerin Specificationfor SourceCapabilitiesThe sink has a similarset of PDOsthat containthe sameinformationdescribingthe Fixed-SupplyPDO SinkBitsParameter31-30 Fixedsupply29 Dual-rolepower28 Highercapability27 Externallypowered26 USBcommunicationscapable25 Dual-roledata24-20 Reserved Shallbe set to zero19-10 Voltagein 50-mVunits9-0 Operationalcurrentin Sinkand SourceCapabilities5 SLVA842 November2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedUSBPD PowerNegotiationsTable6.

6 Variable-Supply(Nonbattery)PDO SinkBitsParameter31-30 Variablesupply(non-battery)29-20 Maximumvoltagein 50-mVunits19-10 Minimumvoltagein 50-mVunits9-0 Operationalcurrentin 10-mAunitsTable7. Battery-SupplyPDO SinkBitsParameter31-30 Battery29-20 Maximumvoltagein 50-mVunits19-10 Minimumvoltagein 50-mVunits9-0 Operationalpowerin Specificationfor SinkCapabilities(PDOs)Morecommonis for the PD sourceto be unawareof the capabilitiesof the sourceadvertisesthecapabilitiesand,if a matchoccurs,the sink returnsa request-dataobject(RDO).Unlessa mismatchoccursor the sourcemustlimit the powergivento a sink partner,the sink PDOsare sink RDOis morecommonthana sink followingtableslist the Fixedand VariableRDOBitsParameter31-30 Reserved Shallbe set to zero29 Objectposition(000bis reservedand shallnot be used)28 GiveBackflag = 027 Capabilitymismatch26 USBcommunicationscapable25No USBsuspend24-20 Reserved Shallbe set to zero19-10 Operatingcurrentin 10-mAunits9-0 Maximumoperatingcurrentin 10-mAunitsTable9.

7 BatteryRDOBitsParameter31-30 Reserved Shallbe set to zero29 Objectposition(000bis Reservedand shallnot be used)28 GiveBackflag = 027 Capabilitymismatch26 USBcommunicationscapable25No USBsuspend24-20 Reserved Shallbe set to zero19-10 Operatingpowerin 250-mWunits9-0 Maximumoperatingpowerin 250-mWunitsUSBP owerDeliverySpecificationfor Sinkand November2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedUSBPD Specificationfor SinkRDOThe mostimportantconceptin the RDOis as follows:the valuein the object-positionfield indicateswhichobjectis referredto by the RDOin the valueof 1 alwaysindicatesthe 5-V fixed-supplyPDObecauseit is the first objectfollowingthe 2 refersto the next PDOand so moreinformation,seeTPS65982 DUSBType-CandUSB-PDController,PowerSwitc h,and High-SpeedMultiplexer(SLVSDB1).3Tx Sinkand SourceCapabilitiesModeHost-InterfaceRegi stersThe configurationregistersfor thesemodesare the transmit(Tx) sourcecapabilitiesregister(address0x32)a nd the transmit(Tx) sink capabilitiesregister(address0x33).

8 The USB-PDpowercapabilitiesare configuredusingthe the transmittedsourceare configuredusingthe Tx sourcecapabilitiesregister(0x32).Thecapa bilitiesof the transmittedsink are configuredusingthe Tx sink capabilitiesregister(0x33).In somecases,a designcan havebothsink and example,a laptopcan sourceat least5 Vto chargeaccessoriesfromthe laptopbatterybut can also chargethe batteryat up to 20 V. This type ofapplicationis calleda dual-roleport (DRP)and mustsometimesinitiateor acceptpowerrole describesthe initialPD powernegotiation,and thereforethe hardwarethat sourcespowerisonly a sourceand DFP,and the hardwarethat sinkspoweris only a Sinkand UFPthat operatesin the useris developinga source-onlydesign,suchas an AC-DCwall adapter,the Type-Cport is set touse a pullupresistor(Rp)only,and the PD policyis set to rejectpowerrole swapsfromthe far source,this chapteronly describeshow to analyzeand modifythe Tx sourcecapabilitiesregister(0x32),and that the TPS65982-EVMreceivesexternalpowerfroma traditional20-VDC the useris developinga sink-onlydesign,suchas a bus-poweredexternalharddrive,the Type-Cport isset to use a pulldownresistor(Rd)

9 Only,and the PD policyis set to rejectpowerrole swapsfromthe TPS6598xFW automaticallyrejectspowerrole swapsto becomethe sourceif the deviceisoperatingin deadbatteryor no the sink,this chapteronly describeshow to analyzeandmodifythe Tx sink capabilitiesregister(0x32),and that the TPS65982-EVMalwaysoperatesin deadbatteryor no SourceCapabilitiesExampleSettingsThe TPS6598xFirmwareConfigurationtool, , containsmanyexampleprojectswith differentsettingsfor sink and sourcecapabilitiesthat are transmittedto the far end of the Type-CcableduringaPD this example,selectthe accessedby clickingtheProjectmenuandselectingtheNew Projectoptionfromthe drop-downmenuof the configurationof the transmittedsourcecapabilitiesis set in the Tx Sinkand SourceCapabilitiesModeHost-InterfaceRegi sters7 SLVA842 November2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedUSBPD PowerNegotiationsFigure1.

10 Tx showsthe Tx sourcecapabilitiesregister(0x32)for exampleusesthreesourcePDOswhichare displayedin theSourcePDO1,SourcePDO2, andSourcePDO3sectionof theRegistertab . To showexactly3 PDOs,theNumberof SourcePDOsfield at the top of theRegistertabmustbe set to decimal3. Figure2 showsa capturedPD tracewhichverifiesthat the datain the Tx sourcecapabilitiesregisteris transmittedto the sink whena validType-Cconnectionis PD Traceof Tx SourceCapabilitiesTx Sinkand November2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedUSBPD SinkCapabilitiesExampleSettingsThe configurationof the transmittedsink capabilitiesis set in the Tx sink capabilitiesregisterat Tx showsthe Tx sink capabilitiesregister(0x33)for exampleusestwo sink PDOs,whichare displayedin theSinkPDO1andSinkPDO2sectionof theRegistertab. To showexactly2 PDOs,theNumberof SinkPDOsfield at the top oftheRegistertab mustbe set to decimal2.