ALARMwww

ADS7955-Q1www.
ti.
comSLAS814–DECEMBER201110-Bit,1MSPS,8-Channel,Single-Ended,MicroPower,SerialInterfaceADCCheckforSamples:ADS7955-Q11FEATURESDESCRIPTIONTheADS7955-Q1isa10-bitmultichannelQualifiedforAutomotiveApplicationsanalog-to-digitalconverter.
1-MHzSampleRateSerialDevicesThedeviceincludesacapacitorbasedSARA/D10-BitResolutionconverterwithinherentsampleandhold.
ZeroLatencyThedeviceacceptsawideanalogsupplyrangefrom20-MHzSerialInterface2.
7Vto5.
25V.
VerylowpowerconsumptionmakesAnalogSupplyRange:2.
7to5.
25Vthisdevicesuitableforbattery-poweredandisolatedpowersupplyapplications.
I/OSupplyRange:1.
7to5.
25VTwoSWSelectableUnipolar,InputRanges:0Awide1.
7Vto5.
25VI/Osupplyrangefacilitatesato2.
5Vand0to5Vglue-lessinterfacewiththemostcommonlyusedCMOSdigitalhosts.
AutoandManualModesforChannelSelection8-ChannelDevicecanShare16ChannelTheserialinterfaceiscontrolledbyCSandSCLKforeasyconnectionwithmicroprocessorsandDSP.
DeviceFootprintTwoProgrammableAlarmLevelsperChannelTheinputsignalissampledwiththefallingedgeofCS.
ItusesSCLKforconversion,serialdataoutput,FourIndividuallyConfigurableGPIOsforandreadingserialdatain.
ThedeviceallowsautoTSSOPPackageDevicessequencingofpreselectedchannelsormanualTypicalPowerDissipation:14.
5mW(+VA=5selectionofachannelforthenextconversioncycle.
V,+VBD=3V)at1MSPSTherearetwosoftwareselectableinputranges(0V-Power-DownCurrent(1μA)2.
5Vand0V-5V),fourindividuallyconfigurableInputBandwidth(47MHzat3dB)GPIOs,andtwoprogrammablealarmthresholdsper30-PinTSSOPPackagechannel.
Thesefeaturesmakethedevicesuitableformostdataacquisitionapplications.
APPLICATIONSThedeviceoffersanattractivepower-downfeature.
ThisisextremelyusefulforpowersavingwhenthePLC/IPCdeviceisoperatedatlowerconversionspeeds.
BatteryPoweredSystemsMedicalInstrumentationDigitalPowerSuppliesTouchScreenControllersHigh-SpeedDataAcquisitionSystemsHigh-SpeedClosed-LoopSystems1Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.
PRODUCTIONDATAinformationiscurrentasofpublicationdate.
Copyright2011,TexasInstrumentsIncorporatedProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.
Productionprocessingdoesnotnecessarilyincludetestingofallparameters.
ADS7955-Q1SLAS814–DECEMBER2011www.
ti.
comThisintegratedcircuitcanbedamagedbyESD.
TexasInstrumentsrecommendsthatallintegratedcircuitsbehandledwithappropriateprecautions.
Failuretoobserveproperhandlingandinstallationprocedurescancausedamage.
ESDdamagecanrangefromsubtleperformancedegradationtocompletedevicefailure.
Precisionintegratedcircuitsmaybemoresusceptibletodamagebecauseverysmallparametricchangescouldcausethedevicenottomeetitspublishedspecifications.
ADS7955-Q1BLOCKDIAGRAMNOTE:n*isnumberofchannels(16,12,8,or4)dependingonthedevicefromtheADS79XXproductfamily.
NOTE:4numberofGPIOareavailableinTSSOPpackagedevice.
ORDERINGINFORMATION-10-BITMAXIMUMNOMISSINGMAXIMUMINTEGRALCODESATNUMBEROFORDERABLEPARTTADIFFERENTIALPACKAGETOP-SIDEMARKINGLINEARITYRESOLUTIONCHANNELSNUMBERLINEARITY(LSB)(LSB)(BIT)–40°Cto125°C±0.
5±0.
510830pinTSSOP-DBTADS7955QDBTRQ1ADS7955Q1ABSOLUTEMAXIMUMRATINGS(1)VALUEUNITAINPorCHntoAGND–0.
3to+VA+0.
3V+VAtoAGND,+VBDtoBDGND–0.
3to+7.
0VDigitalinputvoltagetoBDGND–0.
3to(7.
0)VDigitaloutputtoBDGND–0.
3to(+VA+0.
3)VOperatingtemperaturerange–40to125°CStoragetemperaturerange–65to150°CJunctiontemperature150°CPowerdissipation(TJMax–TA)/θJADBTpackagedversionsratedforMSL3260CperJSTD-020specificationsHumanBodyModel(HBM)ESD,ClassH2perQ100-0022kVMachineModel(MM)ESD,ClassM2perQ100-003200VChargedDeviceModel(CDM)ESD,ClassC3B2perQ100-011Maximumwithstandvoltage>500to≤to750VVwithcornerpins>750Latchup(perJESD78)ClassI(1)Stressesabovethoselistedunder"AbsoluteMaximumRatings"maycausepermanentdamagetothedevice.
Exposuretoabsolutemaximumconditionsforextendedperiodsmayaffectdevicereliability.
2SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
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comSLAS814–DECEMBER2011THERMALINFORMATIONADS7955-Q1THERMALMETRIC(1)DBTUNITS30PINSθJAJunction-to-ambientthermalresistance(2)89.
83θJCtopJunction-to-case(top)thermalresistance(3)22.
94θJBJunction-to-boardthermalresistance(4)43.
13°C/WψJTJunction-to-topcharacterizationparameter(5)0.
77ψJBJunction-to-boardcharacterizationparameter(6)42.
52θJCbotJunction-to-case(bottom)thermalresistance(7)22.
94(1)Formoreinformationabouttraditionalandnewthermalmetrics,seetheICPackageThermalMetricsapplicationreport,SPRA953.
(2)Thejunction-to-ambientthermalresistanceundernaturalconvectionisobtainedinasimulationonaJEDEC-standard,high-Kboard,asspecifiedinJESD51-7,inanenvironmentdescribedinJESD51-2a.
(3)Thejunction-to-case(top)thermalresistanceisobtainedbysimulatingacoldplatetestonthepackagetop.
NospecificJEDEC-standardtestexists,butaclosedescriptioncanbefoundintheANSISEMIstandardG30-88.
(4)Thejunction-to-boardthermalresistanceisobtainedbysimulatinginanenvironmentwitharingcoldplatefixturetocontrolthePCBtemperature,asdescribedinJESD51-8.
(5)Thejunction-to-topcharacterizationparameter,ψJT,estimatesthejunctiontemperatureofadeviceinarealsystemandisextractedfromthesimulationdataforobtainingθJA,usingaproceduredescribedinJESD51-2a(sections6and7).
(6)Thejunction-to-boardcharacterizationparameter,ψJB,estimatesthejunctiontemperatureofadeviceinarealsystemandisextractedfromthesimulationdataforobtainingθJA,usingaproceduredescribedinJESD51-2a(sections6and7).
(7)Thejunction-to-case(bottom)thermalresistanceisobtainedbysimulatingacoldplatetestontheexposed(power)pad.
NospecificJEDECstandardtestexists,butaclosedescriptioncanbefoundintheANSISEMIstandardG30-88.
ELECTRICALCHARACTERISTICS+VA=2.
7Vto5.
25V,+VBD=1.
7Vto5.
25V,Vref=2.
5V±0.
1V,TA=-40°Cto125°C,fsample=1MHz(unlessotherwisenoted)PARAMETERTESTCONDITIONSMINTYPMAXUNITANALOGINPUTRange10VrefFull-scaleinputspan(1)VRange2while2Vref≤+VA02*VrefVREFRange1–0.
20+0.
20AbsoluteinputrangeV2*VREFRange2while2Vref≤+VA–0.
20+0.
20Inputcapacitance15ρFInputleakagecurrentTA=125°C61nASYSTEMPERFORMANCEResolution10BitsNomissingcodes10BitsIntegrallinearity–0.
5±0.
20.
5LSB(2)Differentiallinearity–0.
5±0.
20.
5LSBOffseterror(3)–1.
5±0.
51.
5LSBRange1–1±0.
11GainerrorLSBRange2±0.
1SAMPLINGDYNAMICSConversiontime20MHzSCLK800nSecAcquisitiontime325nSecMaximumthroughputrate20MHzSCLK1.
0MHzAperturedelay5nsecStepresponse150nsecOvervoltagerecovery150nsec(1)Idealinputspan;doesnotincludegainoroffseterror.
(2)LSBmeansLeastSignificantBit.
(3)Measuredrelativetoanidealfull-scaleinputCopyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback3ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
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comELECTRICALCHARACTERISTICS(continued)+VA=2.
7Vto5.
25V,+VBD=1.
7Vto5.
25V,Vref=2.
5V±0.
1V,TA=-40°Cto125°C,fsample=1MHz(unlessotherwisenoted)PARAMETERTESTCONDITIONSMINTYPMAXUNITDYNAMICCHARACTERISTICSTotalharmonicdistortion(4)100kHz–80dBSignal-to-noiseratio100kHz60dBSignal-to-noise+distortion100kHz60Spuriousfreedynamicrange100kHz82dBFullpowerbandwidthAt–3dB47MHzAnyoff-channelwith100kHz,Full-scaleinputto–95channelbeingsampledwithDCinput.
Channel-to-channelcrosstalkdBFrompreviouslysampledtochannelwith100kHz,–85Full-scaleinputtochannelbeingsampledwithDCinput.
EXTERNALREFERENCEINPUTVrefreferencevoltageatREFP2.
02.
53.
0VReferenceresistance100kALARMSETTINGHigherthresholdrange000FFCHexLowerthresholdrange000FFCHexDIGITALINPUT/OUTPUTLogicfamilyCMOSVIH0.
7*(+VBD)VIL+VBD=5V0.
8LogiclevelVIL+VBD=3V0.
4VVOHAtIsource=200μAVdd-0.
2VOLAtIsink=200μA0.
4DataformatMSBfirstMSBFirstPOWERSUPPLYREQUIREMENTS+VAsupplyvoltage2.
73.
35.
25V+VBDsupplyvoltage1.
73.
35.
25VAt+VA=2.
7to3.
6Vand1MHzthroughput1.
8mAAt+VA=2.
7to3.
6Vstaticstate1.
051mASupplycurrent(normalmode)At+VA=4.
7to5.
25Vand1MHzthroughput2.
33mAAt+VA=4.
7to5.
25Vstaticstate1.
11.
5mAPower-downstatesupplycurrent1μA+VBDsupplycurrent+VA=5.
25V,fs=1MHz1mAPower-uptime1μSecInvalidconversionsafterpowerupor1NumbersresetTEMPERATURERANGESpecifiedperformance–40125°C(4)Calculatedonthefirstnineharmonicsoftheinputfrequency.
4SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
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comSLAS814–DECEMBER2011TIMINGREQUIREMENTS(seeFigure7andFigure8)Allspecificationstypicalat–40°Cto125°C,+VA=2.
7Vto5.
25V(unlessotherwisespecified)PARAMETERTESTCONDITIONS(1)(2)MINTYPMAXUNIT+VBD=1.
8V16tconvConversiontime+VBD=3V16SCLK+VBD=5V16+VBD=1.
8V40Minimumquietsamplingtimeneededfrombustq+VBD=3V40ns3-statetostartofnextconversion+VBD=5V40+VBD=1.
8V38td1Delaytime,CSlowtofirstdata(DO–15)out+VBD=3V27ns+VBD=5V17+VBD=1.
8V8tsu1Setuptime,CSlowtofirstrisingedgeofSCLK+VBD=3V6ns+VBD=5V4+VBD=1.
8V35td2Delaytime,SCLKfallingtoSDOnextdatabitvalid+VBD=3V27ns+VBD=5V17+VBD=1.
8V7th1Holdtime,SCLKfallingtoSDOdatabitvalid+VBD=3V5ns+VBD=5V3+VBD=1.
8V26td3Delaytime,16thSCLKfallingedgetoSDO3-state+VBD=3V22ns+VBD=5V13+VBD=1.
8V2tsu2Setuptime,SDIvalidtorisingedgeofSCLK+VBD=3V3ns+VBD=5V4+VBD=1.
8V12th2Holdtime,risingedgeofSCLKtoSDIvalid+VBD=3V10ns+VBD=5V6+VBD=1.
8V20tw1PulsedurationCShigh+VBD=3V20ns+VBD=5V20+VBD=1.
8V24td4DelaytimeCShightoSDO3-state+VBD=3V21ns+VBD=5V12+VBD=1.
8V20twhPulsedurationSCLKhigh+VBD=3V20ns+VBD=5V20+VBD=1.
8V20twlPulsedurationSCLKlow+VBD=3V20ns+VBD=5V20+VBD=1.
8V20FrequencySCLK+VBD=3V20MHz+VBD=5V20(1)1.
8Vspecificationsapplyfrom1.
7Vto1.
9V,3Vspecificationsapplyfrom2.
7Vto3.
6V,5Vspecificationsapplyfrom4.
75Vto5.
25V.
(2)With50-pFloadCopyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback5ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
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comDEVICEINFORMATIONPINCONFIGURATION(TOPVIEW)TERMINALFUNCTIONS-TSSOPPACKAGEDEVICENAMEADS7955-Q1PINNAMEI/OFUNCTIONPINNO.
REFERENCE4REFPIReferenceinput3REFMIReferencegroundADCANALOGINPUT8AINPISignalinputtoADC9AINMIADCinputgroundMULTIPLEXER7MXOOMultiplexeroutput20Ch0I19Ch1I18Ch2I17Ch3I14Ch4I13Ch5I12Ch6I11Ch7IAnalogchannelsformultiplexer-Ch8I-Ch9I-Ch10I-Ch11I-Ch12I-Ch13I-Ch14I-Ch15IDIGITALCONTROLSIGNALS23CSIChipselectinput24SCLKISerialclockinput25SDIISerialdatainput6SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
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comSLAS814–DECEMBER2011TERMINALFUNCTIONS-TSSOPPACKAGE(continued)DEVICENAMEADS7955-Q1PINNAMEI/OFUNCTIONPINNO.
26SDOOSerialdataoutputGENERALPURPOSEINPUTS/OUTPUTS:Thesepinshaveprogrammabledualfunctionality.
RefertoTable8forfunctionalityprogramming29GPIO0I/OGeneralpurposeinputoroutputHighalarmorOActivehighoutputindicatinghighalarmorhigh/lowalarmdependingonHigh/Lowalarmprogramming30GPIO1I/OGeneralpurposeinputoroutputLowalarmOActivehighoutputindicatinglowalarm1GPIO2I/OGeneralpurposeinputoroutputRangeISelectsrange:High->Range2/Low->Range12GPIO3I/OGeneralpurposeinputoroutputPDIActivelowpowerdowninputPOWERSUPPLYANDGROUND5,21+VA—Analogpowersupply6,10,22AGND—Analogground28+VBD—DigitalI/Osupply27BDGND—DigitalgroundNCPINS15,16——Pinsinternallynotconnected,donotfloatthesepinsCopyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback7ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
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comTYPICALCHARATERISTICSSUPPLYCURRENTSTATICSUPPLYCURRENTSUPPLYCURRENTvsvsvsSUPPLYVOLTAGESUPPLYVOLTAGEFREE-AIRTEMPERATUREFigure1.
Figure2.
Figure3.
STATICSUPPLYCURRENTSUPPLYCURRENTSUPPLYCURRENTvsvsvsFREE-AIRTEMPERATURESAMPLERATESAMPLERATEFigure4.
Figure5.
Figure6.
8SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
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comSLAS814–DECEMBER2011DETAILEDDESCRIPTIONDEVICEOPERATIONTheADS7955-Q1isa10-bit8-channeldevice.
Figure7andFigure8showdeviceoperationtiming.
DeviceoperationiscontrolledwithCS,SCLK,andSDI.
ThedeviceoutputsitsdataonSDO.
Figure7.
DeviceOperationTimingDiagramEachframebeginswiththefallingedgeofCS.
WiththefallingedgeofCS,theinputsignalfromtheselectedchannelissampled,andtheconversionprocessisinitiated.
Thedeviceoutputsdatawhiletheconversionisinprogress.
The16-bitdatawordcontainsa4-bitchanneladdress,followedbya12-bitconversionresultinMSBfirstformat.
ThereisanoptiontoreadtheGPIOstatusinsteadofthechanneladdress.
(RefertoTable1,Table2,andTable5formoredetails.
)ThedeviceselectsanewmultiplexerchannelonthesecondSCLKfallingedge.
TheacquisitionphasestartsonthefourteenthSCLKrisingedge.
OnthenextCSfallingedgetheacquisitionphasewillend,andthedevicestartsanewframe.
TheTSSOPpackageddevicehasfourGeneralPurposeIO(GPIO)pins,QFNversionshaveonlyoneGPIO.
ThesefourpinscanbeindividuallyprogrammedasGPOorGPI.
Itisalsopossibletousethemforpreassignedfunctions,refertoTable10.
GPOdatacanbewrittenintothedevicethroughtheSDIline.
ThedevicerefreshestheGPOdataontheCSfallingedgeaspertheSDIdatawritteninpreviousframe.
SimilarlythedevicelatchesGPIstatusontheCSfallingedgeandoutputstheGPIdataontheSDOline(ifGPIreadisenabledbywritingDI04=1inthepreviousframe)inthesameframestartingwiththeCSfallingedge.
Copyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback9ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
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comFigure8.
SerialInterfaceTimingDiagramfor10-BitDevicesThefallingedgeofCSclocksoutDO-15(firstbitofthefourbitchanneladdress),andremainingaddressbitsareclockedoutoneveryfallingedgeofSCLKuntilthethirdfallingedge.
TheconversionresultMSBisclockedoutonthe4thSCLKfallingedgeandLSBonthe15th/13th/11thfallingedgerespectivelyforthe10-bitdevice.
Onthe16thfallingedgeofSCLK,SDOgoestothe3-statecondition.
Theconversionendsonthe16thfallingedgeofSCLK.
ThedevicereadsasixteenbitwordontheSDIpinwhileitoutputsthedataontheSDOpin.
SDIdataislatchedoneveryrisingedgeofSCLKstartingwiththe1stclockasshowninFigure8.
CScanbeasserted(pulledhigh)onlyafter16clockshaveelapsed.
Thedevicehastwo(highandlow)programmablealarmthresholdsperchannel.
Iftheinputcrossestheselimits;thedeviceflagsoutanalarmonGPIO0/GPIO1dependingontheGPIOprogramregistersettings(refertoTable10).
Thealarmisasserted(underthealarmconditions)onthe12thfallingedgeofSCLKinthesameframewhenadataconversionisinprogress.
Thealarmoutputisresetonthe10thfallingedgeofSCLKinthenextframe.
Thedeviceoffersapower-downfeaturetosavepowerwhennotinuse.
Therearetwowaystopowerdownthedevice.
ItcanbepowereddownbywritingDI05=1inthemodecontrolregister(refertoTable1,Table2,andTable5);inthiscasethedevicepowersdownonthe16thfallingedgeofSCLKinthenextdataframe.
AnotherwaytopowerdownthedeviceisthroughGPIOinthecaseoftheTSSOPpackageddevice.
GPIO3canactasthePDinput(refertoTable10,toassignthisfunctionalitytoGPIO3).
Thisisanasynchronousandactivelowinput.
ThedevicepowersdowninstantaneouslyafterGPIO3(PD)=0.
ThedevicewillpowerupagainontheCSfallingedgewithDI05=0inthemodecontrolregisterandGPIO3(PD)=1.
CHANNELSEQUENCINGMODESTherearethreemodesforchannelsequencing,namelyManualmode,Auto-1mode,Auto-2mode.
Modeselectionisdonebywritingintothecontrolregister(refertoTable1,Table2,andTable5).
AnewmultiplexerchannelisselectedonthesecondfallingedgeofSCLK(asshowninFigure7)inallthreemodes.
Manualmode:WhenconfiguredtooperateinManualmode,thenextchanneltobeselectedisprogrammedineachframeandthedeviceselectstheprogrammedchannelinthenextframe.
Onpoweruporafterresetthedefaultchannelis'Channel-0'andthedeviceisinManualmode.
Auto-1mode:Inthismodethedevicescanspre-programmedchannelsinascendingorder.
AnewmultiplexerchannelisselectedeveryframeonthesecondfallingedgeofSCLK.
Thereisaseparate'programregister'forpre-programmingthechannelsequence.
Table3andTable4showAuto-1'programregister'settings.
Onceprogrammedthedeviceretains'programregister'settingsuntilthedeviceispowereddown,reset,orreprogrammed.
Itisallowedtoexitandre-entertheAuto-1modeanynumberoftimeswithoutdisturbing'programregister'settings.
TheAuto-1programregisterisresettoFFFF/FFF/FF/Fhexforthe8channeldeviceupondevicepoweruporreset;implyingthedevicescansallchannelsinascendingorder.
10SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
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comSLAS814–DECEMBER2011Auto-2mode:Inthismodetheusercanconfiguretheprogramregistertoselectthelastchannelinthescansequence.
Thedevicescansallchannelsfromchannel0uptoandincludingthelastchannelinascendingorder.
ThemultiplexerchannelisselectedeveryframeonthesecondfallingedgeofSCLK.
Thereisaseparate'programregister'forpre-programmingofthelastchannelinthesequence(multiplexerdepth).
Table6liststhe'Auto-2prog'registersettingsforselectionofthelastchannelinthesequence.
Onceprogrammedthedeviceretainsprogramregistersettingsuntilthedeviceispowereddown,reset,orreprogrammed.
Itisallowedtoexitandre-enterAuto-2modeanynumberoftimes,withoutdisturbingthe'programregister'settings.
OnpoweruporresetthebitsD9-D6oftheAuto-2programregisterareresetto7hexforthe8channeldevice;implyingthedevicescansallchannelsinascendingorder.
DEVICEPROGRAMMINGANDMODECONTROLThefollowingsectiondescribesdeviceprogrammingandmodecontrol.
Thesedevicesfeaturetwotypesofregisterstoconfigureandoperatethedevicesindifferentmodes.
Theseregistersarereferredas'ConfigurationRegisters'.
Therearetwotypesof'ConfigurationRegisters'namely'Modecontrolregisters'and'Programregisters'.
ModeControlRegisterA'Modecontrolregister'isconfiguredtooperatethedeviceinoneofthreechannelsequencingmodes,namelyManualmode,Auto-1Mode,Auto-2Mode.
Itisalsousedtocontroluserprogrammablefeatureslikerangeselection,devicepower-downcontrol,GPIOreadcontrol,andwritingoutputdataintotheGPIO.
ProgramRegistersThe'Programregisters'areusedfordeviceconfigurationsettingsandaretypicallyprogrammedonceonpoweruporafterdevicereset.
Therearedifferentprogramregisterssuchas'Auto-1modeprogramming'forpre-programmingthechannelsequence,'Auto-2modeprogramming'forselectionofthelastchannelinthesequence,'Alarmprogramming'forall16channels(8channels)andGPIOforindividualpinconfigurationasGPIorGPOorapre-assignedfunction.
DEVICEPOWER-UPSEQUENCEThedevicepower-upsequenceisshowninFigure9.
Manualmodeisthedefaultpower-upchannelsequencingmodeandChannel-0isthefirstchannelbydefault.
Asexplainedpreviously,thesedevicesofferProgramRegisterstoconfigureuserprogrammablefeatureslikeGPIO,Alarm,andtopre-programthechannelsequenceforAutomodes.
At'poweruporonreset'theseregistersaresettothedefaultvalueslistedinTable1toTable10.
Itisrecommendedtoprogramtheseregistersonpoweruporafterreset.
Onceconfigured;thedeviceisreadytouseinanyofthethreechannelsequencingmodesnamelyManual,Auto-1,andAuto-2.
Copyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback11ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
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com(1)ThedevicecontinuesitsoperationinManualmodechannel0throughouttheprogrammingsequenceandoutputsvalidconversionresults.
Itispossibletochangechannel,range,GPIObyinsertingextraframesinbetweentwoprogrammingblocks.
Itisalsopossibletobypassanyprogrammingblockiftheuserdoesnotintenttousethatfeature.
(2)Itispossibletoreprogramthedeviceatanytimeduringoperation,regardlessofwhatmodethedeviceisin.
Duringprogrammingthedevicecontinuesitsoperationinwhatevermodeitisinandoutputsvaliddata.
Figure9.
DevicePower-UpSequenceOPERATINGINMANUALMODEThedetailsregardingenteringandrunninginManualchannelsequencingmodeareillustratedinFigure10.
Table1liststheModeControlRegistersettingsforManualmodeindetail.
NotethattherearenoProgramRegistersformanualmode.
12SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
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comSLAS814–DECEMBER2011Figure10.
EnteringandRunninginManualChannelSequencingModeCopyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback13ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
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comTable1.
ModeControlRegisterSettingsforManualModeDESCRIPTIONRESETBITSLOGICSTATEFUNCTIONSTATEDI15-1200010001SelectsManualModeDI1101EnablesprogrammingofbitsDI06-00.
0DeviceretainsvaluesofDI06-00fromthepreviousframe.
DI10-070000Thisfourbitdatarepresentstheaddressofthenextchanneltobeselectedinthenextframe.
DI10:MSBandDI07:LSB.
e.
g.
0000representschannel-0,0001representschannel-1etc.
DI0600Selects2.
5Vi/prange(Range1)1Selects5Vi/prange(Range2)DI0500Devicenormaloperation(nopowerdown)1Devicepowersdownon16thSCLKfallingedgeDI040SDOoutputscurrentchanneladdressofthechannelonDO15.
.
12followedby12bitconversion0resultonDO11.
.
00.
1GPIO3-GPIO0data(bothinputandoutput)ismappedontoDO15-DO12intheordershownbelow.
LowerdatabitsDO11-DO00represent12-bitconversionresultofthecurrentchannel.
DOI5DOI4DOI3DOI2GPIO3(1)GPIO2(1)GPIO1(1)GPIO0(1)DI03-000000GPIOdataforthechannelsconfiguredasoutput.
Devicewillignorethedataforthechannelwhichisconfiguredasinput.
SDIbitandcorrespondingGPIOinformationisgivenbelowDI03DI02DI01DI00GPIO3(2)GPIO2(2)GPIO1(2)GPIO0(2)(1)GPIO1to3areavailableonlyinTSSOPpackageddevices.
QFNdeviceoffersGPIO0only.
(2)GPIO1to3areavailableonlyinTSSOPpackageddevices.
QFNdeviceoffersGPIO0only.
14SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
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comSLAS814–DECEMBER2011OPERATINGINAUTO-1MODEThedetailsregardingenteringandrunninginAuto-1channelsequencingmodeareillustratedintheflowchartinFigure11.
Table2liststheModeControlRegistersettingsforAuto-1modeindetail.
Figure11.
EnteringandRunninginAuto-1ChannelSequencingModeCopyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback15ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
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comTable2.
ModeControlRegisterSettingsforAuto-1ModeDESCRIPTIONRESETBITSLOGICSTATEFUNCTIONSTATEDI15-1200010010SelectsAuto-1ModeDI1101EnablesprogrammingofbitsDI10-00.
0DeviceretainsvaluesofDI10-00frompreviousframe.
DI1001ThechannelcounterisresettothelowestprogrammedchannelintheAuto-1ProgramRegister0Thechannelcounterincrementseveryconversion(Noreset)DI09-07000xxxDonotcareDI0600Selects2.
5Vi/prange(Range1)1Selects5Vi/prange(Range2)DI0500Devicenormaloperation(nopowerdown)1Devicepowersdownonthe16thSCLKfallingedgeDI040SDOoutputscurrentchanneladdressofthechannelonDO15.
.
12followedby12-bitconversion0resultonDO11.
.
00.
1GPIO3-GPIO0data(bothinputandoutput)ismappedontoDO15-DO12intheordershownbelow.
LowerdatabitsDO11-DO00represent12-bitconversionresultofthecurrentchannel.
DO15DO14DO13DO12GPIO3(1)GPIO2(1)GPIO1(1)GPIO0(1)DI03-000000GPIOdataforthechannelsconfiguredasoutput.
Devicewillignorethedataforthechannelwhichisconfiguredasinput.
SDIbitandcorrespondingGPIOinformationisgivenbelowDI03DI02DI01DI00GPIO3(2)GPIO2(2)GPIO1(2)GPIO0(2)(1)GPIO1to3areavailableonlyinTSSOPpackageddevices.
QFNdeviceoffersGPIO0only.
(2)GPIO1to3areavailableonlyinTSSOPpackageddevices.
QFNdeviceoffersGPIO0only.
16SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
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comSLAS814–DECEMBER2011TheAuto-1ProgramRegisterisprogrammed(onceonpoweruporreset)topre-selectthechannelsfortheAuto-1sequence.
Auto-1ProgramRegisterprogrammingrequirestwoCSframesforcompleteprogramming.
InthefirstCSframethedeviceenterstheAuto-1registerprogrammingsequenceandinthesecondframeitprogramstheAuto-1ProgramRegister.
RefertoTable2,Table3,andTable4forcompletedetails.
NOTE:Thedevicecontinuesitsoperationinselectedmodeduringprogramming.
SDOisvalid,howeveritisnotpossibletochangetherangeorwriteGPIOdataintothedeviceduringprogramming.
Figure12.
Auto-1RegisterProgrammingFlowchartTable3.
ProgramRegisterSettingsforAuto-1ModeDESCRIPTIONRESETBITSSTATELOGICSTATEFUNCTIONFRAME1DI15-12NA1000DeviceentersAuto-1programsequence.
Deviceprogrammingisdoneinthenextframe.
DI11-00NADonotcareFRAME2DI15-00All1s1(individualbit)Aparticularchannelisprogrammedtobeselectedinthechannelscanningsequence.
Thechannelnumbersaremappedone-to-onewithrespecttotheSDIbits;e.
g.
DI15→Ch15,DI14→Ch14…DI00→Ch00Aparticularchannelisprogrammedtobeskippedinthechannelscanningsequence.
The0(individualbit)channelnumbersaremappedone-to-onewithrespecttotheSDIbits;e.
g.
DI15→Ch15,DI14→Ch14…DI00→Ch00Table4.
MappingofChannelstoSDIBitsSDIBITSDevice(1)DI15DI14DI13DI12DI11DI10DI09DI08DI07DI06DI05DI04DI03DI02DI01DI008ChanXXXXXXXX1/01/01/01/01/01/01/01/0(1)WhenoperatinginAuto-1mode,thedeviceonlyscansthechannelsprogrammedtobeselected.
Copyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback17ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
ti.
comOPERATINGINAUTO-2MODEThedetailsregardingenteringandrunninginAuto-2channelsequencingmodeareillustratedinFigure13.
Table5liststheModeControlRegistersettingsforAuto-2modeindetail.
Figure13.
EnteringandRunninginAuto-2ChannelSequencingMode18SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
ti.
comSLAS814–DECEMBER2011Table5.
ModeControlRegisterSettingsforAuto-2ModeDESCRIPTIONRESETBITSLOGICSTATEFUNCTIONSTATEDI15-1200010011SelectsAuto-2ModeDI1101EnablesprogrammingofbitsDI10-00.
0DeviceretainsvaluesofDI10-00fromthepreviousframe.
DI1001ChannelnumberisresettoCh-00.
0Channelcounterincrementseveryconversion.
(Noreset).
DI09-07000xxxDonotcareDI0600Selects2.
5Vi/prange(Range1)1Selects5Vi/prange(Range2)DI0500Devicenormaloperation(nopowerdown)1Devicepowersdownonthe16thSCLKfallingedgeDI040SDOoutputsthecurrentchanneladdressofthechannelonDO15.
.
12followedbythe12-bit0conversionresultonDO11.
.
00.
1GPIO3-GPIO0data(bothinputandoutput)ismappedontoDO15-DO12intheordershownbelow.
LowerdatabitsDO11-DO00representthe12-bitconversionresultofthecurrentchannel.
DO15DO14DO13DO12GPIO3(1)GPIO2(1)GPIO1(1)GPIO0(1)DI03-000000GPIOdataforthechannelsconfiguredasoutput.
Deviceignoresdataforthechannelwhichisconfiguredasinput.
SDIbitandcorrespondingGPIOinformationisgivenbelowDI03DI02DI01DI00GPIO3(1)GPIO2(1)GPIO1(1)GPIO0(1)(1)GPIO1to3areavailableonlyinTSSOPpackageddevices.
QFNdeviceoffersGPIO0only.
TheAuto-2ProgramRegisterisprogrammed(onceonpoweruporreset)topre-selectthelastchannel(orsequencedepth)intheAuto-2sequence.
UnlikeAuto-1ProgramRegisterprogramming,Auto-2ProgramRegisterprogrammingrequiresonly1CSframeforcompleteprogramming.
SeeFigure14andTable6forcompletedetails.
NOTE:Thedevicecontinuesitsoperationintheselectedmodeduringprogramming.
SDOisvalid,howeveritisnotpossibletochangetherangeorwriteGPIOdataintothedeviceduringprogramming.
Figure14.
Auto-2RegisterProgrammingFlowchartCopyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback19ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
ti.
comTable6.
ProgramRegisterSettingsforAuto-2ModeDESCRIPTIONRESETBITSLOGICSTATEFUNCTIONSTATEDI15-12NA1001Auto-2programregisterisselectedforprogrammingDI11-10NADonotcareDI09-06NAaaaaThis4-bitdatarepresentstheaddressofthelastchannelinthescanningsequence.
DuringdeviceoperationinAuto-2mode,thechannelcounterstartsatCH-00andincrementseveryframeuntilitequals"aaaa".
ThechannelcounterrolesovertoCH-00inthenextframe.
DI05-00NADonotcareCONTINUEDOPERATIONINASELECTEDMODEOnceadeviceisprogrammedtooperateinoneofthemodes,theusermaywanttocontinueoperatinginthesamemode.
ModeControlRegistersettingstocontinueoperatinginaselectedmodearedetailedinTable7.
Table7.
ContinuedOperationinaSelectedModeDESCRIPTIONRESETBITSLOGICSTATEFUNCTIONSTATEDI15-1200010000Thedevicecontinuestooperateintheselectedmode.
InAuto-1andAuto-2modesthechannelcounterincrementsnormally,whereasintheManualmodeitcontinueswiththelastselectedchannel.
ThedeviceignoresdataonDI11-DI00andcontinuesoperatingaspertheprevioussettings.
ThisfeatureisprovidedsothatSDIcanbeheldlowwhennochangesarerequiredintheModeControlRegistersettings.
DI11-00All'0'DeviceignoresthesebitswhenDI15-12issetto0000logicstatePROGRAMMINGALARMTHRESHOLDSTherearetwoAlarmProgramRegistersperchannel,oneforsettingthehighalarmthresholdandtheotherforsettingthelowalarmthreshold.
Foreaseofprogramming,twoalarmprogrammingregistersperchannel,correspondingtofourconsecutivechannels,areassembledintoonegroup(atotaleightregisters).
Therearefoursuchgroupsfor16channeldevicesand3/2/1suchgroupsfor12/8/4channeldevicesrespectively.
ThegroupingofthevariouschannelsforeachdeviceintheADS7955-Q1islistedinTable8.
ThedetailsregardingprogrammingthealarmthresholdsareillustratedintheflowchartinFigure15.
Table9liststhedetailsregardingtheAlarmProgramRegistersettings.
Table8.
GroupingofAlarmProgramRegistersGROUPNO.
REGISTERS0Highandlowalarmforchannel0,1,2,and31Highandlowalarmforchannel4,5,6,and7Eachalarmgrouprequires9CSframesforprogrammingtheirrespectivealarmthresholds.
Inthefirstframethedeviceenterstheprogrammingsequenceandineachsubsequentframeitprogramsoneoftheregistersfromthegroup.
Thedeviceoffersafeaturetoprogramlessthaneightregistersinoneprogrammingsequence.
Thedeviceexitsthealarmthresholdprogrammingsequenceinthenextframeafteritencountersthefirst'ExitAlarmProgram'bithigh.
20SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
ti.
comSLAS814–DECEMBER2011NOTE:Thedevicecontinuesitsoperationinselectedmodeduringprogramming.
SDOisvalid,howeveritisnotpossibletochangetherangeorwriteGPIOdataintothedeviceduringprogramming.
Figure15.
AlarmProgramRegisterProgrammingFlowchartTable9.
AlarmProgramRegisterSettingsDESCRIPTIONBITSRESETSTATELOGICFUNCTIONSTATEFRAME1DI15-12NA1100Deviceenters'alarmprogrammingsequence'forgroup01101Deviceenters'alarmprogrammingsequence'forgroup11110Deviceenters'alarmprogrammingsequence'forgroup21111Deviceenters'alarmprogrammingsequence'forgroup3Note:DI15-12=11bbisthealarmprogrammingrequestforgroupbb.
Here'bb'representsthealarmprogramminggroupnumberinbinaryformat.
DI11-14NADonotcareFRAME2ANDONWARDSCopyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback21ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
ti.
comTable9.
AlarmProgramRegisterSettings(continued)DESCRIPTIONBITSRESETSTATELOGICFUNCTIONSTATEDI15-14NAccWhere"cc"representsthelowertwobitsofthechannelnumberinbinaryformat.
Thedeviceprogramsthealarmforthechannelrepresentedbythebinarynumber"bbcc".
Notethat"bb"isprogrammedinthefirstframe.
DI13NA1Highalarmregisterselection0LowalarmregisterselectionDI12NA0Continuealarmprogrammingsequenceinnextframe1ExitAlarmProgramminginthenextframe.
Note:IfthealarmprogrammingsequenceisnotterminatedusingthisfeaturethenthedevicewillremaininthealarmprogrammingsequencestateandallSDIdatawillbetreatedasalarmthresholds.
DI11-10NAxxDonotcareDI09-00AllonesforhighThis10-bitdatarepresentsthealarmthreshold.
The10-bitalarmthresholdiscomparedwiththeupper10-bitalarmregisterwordofthe12-bitconversionresult.
Thedevicesetsoffanalarmwhentheconversionresultishigher(HighandallzerosforAlarm)orlower(LowAlarm)thanthisnumber.
For10-bitdevices,all10bitsoftheconversionresultarelowalarmregistercomparedwiththesetthreshold.
For8-bitdevices,all8bitsoftheconversionresultarecomparedwithDI09toDI02andDI00,01are'donotcare'.
PROGRAMMINGGPIOREGISTERSNOTEGPIO1to3areavailableonlyinTSSOPpackageddevices.
TheQFNdeviceoffers'GPIO0'only.
Asaresult,allreferencesrelatedto'GPIO0'onlyarevalidinthecaseofQFNpackagedevices.
ThedevicehasfourGeneralPurposeInputandOutput(GPIO)pins.
EachofthefourpinscanbeindependentlyprogrammedasGeneralPurposeOutput(GPO)orGeneralPurposeInput(GPI).
ItisalsopossibletousetheGPIOsforsomepre-assignedfunctions(refertoTable10fordetails).
GPOdatacanbewrittenintothedevicethroughtheSDIline.
ThedevicerefreshestheGPOdataoneveryCSfallingedgeaspertheSDIdatawritteninthepreviousframe.
Similarly,thedevicelatchesGPIstatusontheCSfallingedgeandoutputsitonSDO(ifGPIisreadenabledbywritingDI04=1duringthepreviousframe)inthesameframestartingontheCSfallingedge.
ThedetailsregardingprogrammingtheGPIOregistersareillustratedintheflowchartinFigure16.
Table10liststhedetailsregardingGPIORegisterprogrammingsettings.
22SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
ti.
comSLAS814–DECEMBER2011NOTE:Thedevicecontinuesitsoperationinselectedmodeduringprogramming.
SDOisvalid,howeveritisnotpossibletochangetherangeorwriteGPIOdataintothedeviceduringprogramming.
Figure16.
GPIOProgramRegisterProgrammingFlowchartTable10.
GPIOProgramRegisterSettingsDESCRIPTIONRESETBITSLOGICSTATEFUNCTIONSTATEDI15-12NA0100DeviceselectsGPIOProgramRegistersforprogramming.
DI11-100000Donotprogramthesebitstoanylogicstateotherthan'00'DI0901DeviceresetsallregistersinthenextCSframetotheresetstateshowninthecorrespondingtables(italsoresetsitself).
0DevicenormaloperationDI0801DeviceconfiguresGPIO3asthedevicepower-downinput.
0GPIO3remainsgeneralpurposeIorO.
Program0forQFNpackageddevices.
DI0701DeviceconfiguresGPIO2asdevicerangeinput.
0GPIO2remainsgeneralpurposeIorO.
Program0forQFNpackageddevices.
DI06-04000000GPIO1andGPIO0remaingeneralpurposeIorO.
ValidsettingforQFNpackageddevices.
xx1DeviceconfiguresGPIO0as'highorlow'alarmoutput.
Thisisanactivehighoutput.
GPIO1remainsgeneralpurposeIorO.
ValidsettingforQFNpackageddevices.
010DeviceconfiguresGPIO0ashighalarmoutput.
Thisisanactivehighoutput.
GPIO1remainsgeneralpurposeIorO.
ValidsettingforQFNpackageddevices.
100DeviceconfiguresGPIO1aslowalarmoutput.
Thisisanactivehighoutput.
GPIO0remainsgeneralpurposeIorO.
SettingnotallowedforQFNpackageddevices.
110DeviceconfiguresGPIO1aslowalarmoutputandGPIO0asahighalarmoutput.
Theseareactivehighoutputs.
SettingnotallowedforQFNpackageddevices.
Note:ThefollowingsettingsarevalidforGPIOwhicharenotassignedaspecificfunctionthroughbitsDI08.
.
04DI0301GPIO3pinisconfiguredasgeneralpurposeoutput.
Program1forQFNpackageddevices.
0GPIO3pinisconfiguredasgeneralpurposeinput.
SettingnotallowedforQFNpackageddevices.
DI0201GPIO2pinisconfiguredasgeneralpurposeoutput.
Program1forQFNpackageddevices.
0GPIO2pinisconfiguredasgeneralpurposeinput.
SettingnotallowedforQFNpackageddevices.
DI0101GPIO1pinisconfiguredasgeneralpurposeoutput.
Program1forQFNpackageddevices.
0GPIO1pinisconfiguredasgeneralpurposeinput.
SettingnotallowedforQFNpackageddevices.
DI0001GPIO0pinisconfiguredasgeneralpurposeoutput.
ValidsettingforQFNpackageddevices.
Copyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback23ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
ti.
comTable10.
GPIOProgramRegisterSettings(continued)DESCRIPTIONRESETBITSLOGICSTATEFUNCTIONSTATE0GPIO0pinisconfiguredasgeneralpurposeinput.
ValidsettingforQFNpackageddevices.
24SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
ti.
comSLAS814–DECEMBER2011APPLICATIONINFORMATIONANALOGINPUTTheADS7955-Q1deviceoffersa10-bitADCwith8-channelmultiplexersforanaloginput.
ThemultiplexeroutputisavailableontheMXOpin.
AINPistheADCinputpin.
Thedevicesoffersflexibilityforasystemdesignerasbothsignalsareaccessibleesternally.
TypicallyitisconvenienttoshortMXOtotheAINPpinsothatsignalinputtoeachmultiplexerchannelcanbeprocessedindependently.
Inthisconditionitisrecommendedtolimitsourceimpedanceto50orless.
Highersourceimpedancemayaffectthesignalsettlingtimeafteramultiplexerchannelchange.
Thisconditioncanaffectlinearityandtotalharmonicdistortion.
GPIO1to3areavailableonlyinTSSOPpackageddevices.
QFNdeviceoffers'GPIO0'only.
Asaresultallreferencesrelatedto'GPIO0'onlyarevalidincaseofQFNpackagedevices.
Figure17.
TypicalApplicationDiagramShowingMXOShortedtoAINPAnotheroptionistoaddacommonADCdriverbufferbetweentheMXOandAINPpins.
Thisrelaxestherestrictiononsourceimpedancetoalargeextent.
Refertothetypicalcharacteristicssectionfortheeffectofsourceimpedanceondeviceperformance.
Thetypicalcharacteristicsshowthatthedevicehasrespectableperformancewithupto1ksourceimpedance.
Thistopology(includingacommonADCdriver)isusefulwhenallchannelsignalsarewithintheacceptablerangeoftheADC.
Inthiscasetheusercansaveonsignalconditioningcircuitforeachchannel.
Copyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback25ProductFolderLink(s):ADS7955-Q1ADS7955-Q1SLAS814–DECEMBER2011www.
ti.
comGPIO1to3areavailableonlyinTSSOPpackageddevices.
QFNdeviceoffers'GPIO0'only.
Asaresultallreferencesrelatedto'GPIO0'onlyarevalidincaseofQFNpackagedevices.
Figure18.
TypicalApplicationDiagramShowingCommonBuffer/PGAforallChannelsWhentheconvertersamplesaninput,thevoltagedifferencebetweenAINPandAGNDiscapturedontheinternalcapacitorarray.
The(peak)inputcurrentthroughtheanaloginputsdependsuponanumberoffactors:samplerate,inputvoltage,andsourceimpedance.
ThecurrentintotheADS7955-Q1chargestheinternalcapacitorarrayduringthesampleperiod.
Afterthiscapacitancehasbeenfullycharged,thereisnofurtherinputcurrent.
Whentheconvertergoesintoholdmode,theinputimpedanceisgreaterthan1GΩ.
Caremustbetakenregardingtheabsoluteanaloginputvoltage.
Tomaintainlinearityoftheconverter,theCh0.
.
ChnandAINPinputsshouldbewithinthelimitsspecified.
Outsideoftheseranges,converterlinearitymaynotmeetspecifications.
Figure19.
ADCandMuxEquivalentCircuit26SubmitDocumentationFeedbackCopyright2011,TexasInstrumentsIncorporatedProductFolderLink(s):ADS7955-Q1ADS7955-Q1www.
ti.
comSLAS814–DECEMBER2011REFERENCETheADS7955-Q1canoperatewithanexternal2.
5V±10mVreference.
Aclean,lownoise,well-decoupledreferencevoltageontheREFpinisrequiredtoensuregoodperformanceoftheconverter.
Alownoiseband-gapreferenceliketheREF5025canbeusedtodrivethispin.
A10-μFceramicdecouplingcapacitorisrequiredbetweentheREFandGNDpinsoftheconverter.
Thecapacitorshouldbeplacedascloseaspossibletothepinsofthedevice.
POWERSAVINGTheADS7955-Q1deviceoffersapower-downfeaturetosavepowerwhennotinuse.
Therearetwowaystopowerdownthedevice.
ItcanbepowereddownbywritingDI05=1intheModeControlregister(refertoTable1,Table2andTable5);inthiscasethedevicepowersdownonthe16thfallingedgeofSCLKinthenextdataframe.
AnotherwaytopowerdownthedeviceisthroughGPIO.
GPIO3canactasaPDinput(refertoTable10,forassigningthisfunctionalitytoGPIO3).
Thisisanasynchronousandactivelowinput.
ThedevicepowersdowninstantaneouslyafterGPIO3(PD)=0.
ThedevicewillpowerupagainontheCSfallingedgewhileDI05=0intheModeControlregisterandGPIO3(PD)=1.
DIGITALOUTPUTAsdiscussedpreviouslyintheDeviceOperationsection,thedigitaloutputoftheADS7955-Q1deviceisSPIcompatible.
Thefollowingtableliststheoutputcodescorrespondingtovariousanaloginputvoltages.
Table11.
IdealInputVoltagesandOutputCodesDESCRIPTIONANALOGVALUEDIGITALOUTPUTFullscalerangeRange1→VrefRange2→2*VrefSTRAIGHTBINARYLeastsignificantbit(LSB)Vref/10242Vref/1024BINARYCODEHEXCODEFullscaleVref–1LSB2Vref–1LSB11111111113FFMidscaleVref/2Vref1000000000200Midscale–1LSBVref/2–1LSBVref–1LSB01111111111FFZero0V0V0000000000000Copyright2011,TexasInstrumentsIncorporatedSubmitDocumentationFeedback27ProductFolderLink(s):ADS7955-Q1PACKAGEOPTIONADDENDUMwww.
ti.
com11-Apr-2013Addendum-Page1PACKAGINGINFORMATIONOrderableDeviceStatus(1)PackageTypePackageDrawingPinsPackageQtyEcoPlan(2)Lead/BallFinishMSLPeakTemp(3)OpTemp(°C)Top-SideMarkings(4)SamplesADS7955QDBTRQ1ACTIVETSSOPDBT302000Green(RoHS&noSb/Br)CUNIPDAULevel-3-260C-168HR-40to125ADS7955Q1(1)Themarketingstatusvaluesaredefinedasfollows:ACTIVE:Productdevicerecommendedfornewdesigns.
LIFEBUY:TIhasannouncedthatthedevicewillbediscontinued,andalifetime-buyperiodisineffect.
NRND:Notrecommendedfornewdesigns.
Deviceisinproductiontosupportexistingcustomers,butTIdoesnotrecommendusingthispartinanewdesign.
PREVIEW:Devicehasbeenannouncedbutisnotinproduction.
Samplesmayormaynotbeavailable.
OBSOLETE:TIhasdiscontinuedtheproductionofthedevice.
(2)EcoPlan-Theplannedeco-friendlyclassification:Pb-Free(RoHS),Pb-Free(RoHSExempt),orGreen(RoHS&noSb/Br)-pleasecheckhttp://www.
ti.
com/productcontentforthelatestavailabilityinformationandadditionalproductcontentdetails.
TBD:ThePb-Free/Greenconversionplanhasnotbeendefined.
Pb-Free(RoHS):TI'sterms"Lead-Free"or"Pb-Free"meansemiconductorproductsthatarecompatiblewiththecurrentRoHSrequirementsforall6substances,includingtherequirementthatleadnotexceed0.
1%byweightinhomogeneousmaterials.
Wheredesignedtobesolderedathightemperatures,TIPb-Freeproductsaresuitableforuseinspecifiedlead-freeprocesses.
Pb-Free(RoHSExempt):ThiscomponenthasaRoHSexemptionforeither1)lead-basedflip-chipsolderbumpsusedbetweenthedieandpackage,or2)lead-baseddieadhesiveusedbetweenthedieandleadframe.
ThecomponentisotherwiseconsideredPb-Free(RoHScompatible)asdefinedabove.
Green(RoHS&noSb/Br):TIdefines"Green"tomeanPb-Free(RoHScompatible),andfreeofBromine(Br)andAntimony(Sb)basedflameretardants(BrorSbdonotexceed0.
1%byweightinhomogeneousmaterial)(3)MSL,PeakTemp.
--TheMoistureSensitivityLevelratingaccordingtotheJEDECindustrystandardclassifications,andpeaksoldertemperature.
(4)MultipleTop-SideMarkingswillbeinsideparentheses.
OnlyoneTop-SideMarkingcontainedinparenthesesandseparatedbya"~"willappearonadevice.
IfalineisindentedthenitisacontinuationofthepreviouslineandthetwocombinedrepresenttheentireTop-SideMarkingforthatdevice.
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016.
46.
958.
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