1656A

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ADS1131REF and ADS1231REF

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ADS1131REF TI1 | Alldatasheet

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PDF pages: 31

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Datasheet sections

1 GettingStarted
2 Weigh ScaleMode
3 AnalysisMode
4 UsingthePC Software
5 SerialConsole
6 Hardware
1 ADS1x31REF Controlsand Connectors
6 ADS1231REF PC SoftwareDisplay
7 ADS1x31REF AverageData
8 ADS1x31REF Hardware BlockDiagram
9 ADS1x31REF PCB —Top Side
10 ADS1x31REF PCB —Layer1
11 ADS1x31REF PCB —Layer2
12 ADS1x31REF PCB —BottomSide
13 ADS1x31REF Schematic—ADC
14 ADS1x31REF Schematic—MCU
15 ADS1x31REF Schematic—USB
1 UnitConversionFactorsand DisplayFormats
2 ParametersinConfigurationMode
3 Modes and Example Displays
4 VoltageDisplayRanges
5 ParametersinAnalysisMode
6 ConsoleMode Commands
7 Load CellHeader Pinout
8 TerminalBlockPinout
9 ADS1x31REF BillofMaterials
2 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

User's Guide SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF The ADS1131REF and the ADS1231REF are referencedesigns for delta-sigmaanalog-to-digital converters(ADCs). The ADS1131REF containsthe ADS1131 18-bitdevice,whilethe ADS1231REF containsthe ADS1231 24-bitdevice.Both systems containallthe circuitryand user interfaceelements needed fora weigh-scaledigitizer,and aremeant as examples ofa good designfora basicweigh-scale system.Each system isalsosuitableforgeneralevaluationoftherespectivelyinstalledADC. Throughout thisdocument,the term ADS1x31REF isused to referto the common featuresand functionsforboth systems. The ADS1x31REF hardwarehas thefollowingfeatures:

ADS1131 ADC fortheADS1131REF and ADS1231 ADC fortheADS1231REF
Connectionsforloadcellsorothervoltagesources
Low-sideexcitationswitchon theloadcellheaderconnector
Ample EMI/RFIsuppressionbetween theADC and restofdesign
Eight-digitstarburstLCD readout
USB connectionforfirmwareupdatesand remotecontrol
Designedforverylowpower consumption
Battery(9V)orwallpower Version1.0.0ofthefirmwareincludesthefollowingfeatures:
Weigh-scalemode withtwo-pointcalibration
Completeconfigurationofthedevice
Real-timepeak-to-peakand RMS noisecalculation
Autorangingvoltagedisplay
Noisedisplayedinvolts,codes,and bits
Voltagedisplayedinvoltsorcodes
Adjustableaveragingmode
Raw hexadecimalcode display
Simpleand fastconfiguration
Parameterssaved tointernalflashmemory
Computer link GraphicalPC softwareisalsoprovidedforhistogramdisplay,datalogging,and devicecontrol. We welcome bug reportsand suggestionsforadditionalfeatures;pleasecontacttheTexas Instruments PrecisionAnalogApplicationsGroup. Hypertermisa trademarkofMicrosoftCorporation. Windows isa registeredtrademarkofMicrosoftCorporation. Allothertrademarksarethepropertyoftheirrespectiveowners. 1SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

www.ti.com GettingStarted

1 GettingStarted

A diagramoftheADS1x31REF isshown inFigure1. Figure1.ADS1x31REF Controlsand Connectors

1.1 OperatingModes

The ADS1x31REF operatesinone ofthreemodes:

Scalemode: When themode selectswitchisinScaleposition,theADS1x31REF actsas a basic weighscale.The scalehas tare,range,and calibratefunctions,and can displaymetric(SI)units.Other parameterscan be configuredinconfigurationscreens.Scalemode isdescribedindetailinSection2.
Analysismode: When themode selectswitchisinAnalysisposition,codes aretakendirectlyfromthe installedADS deviceand variousmeasurements aremade upon them.Severalmeasurements are available,includingraw display,voltage,RMS noise,and peak-to-peakmeasurements.The ADS1131 orADS1231 can alsobe configureddirectlyfromthismode. Analysismode isdescribedindetailin Section3.
Configurationmode: ParametersgoverningtheoperationoftheADS1x31REF can be viewedand alteredinthismode. Scaleand Analysismodes have differentoptionsinconfigurationmode: configurationforScalemode isdescribedinSection2.4,and configurationforAnalysismode is describedinSection3.4. 3SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

GettingStarted www.ti.com

1.2 Controls

The main controlsfortheADS1x31REF arethefourbuttonsand themode selectionslide-switch(see Figure1). The slide-switchselectsbetween weigh-scale(Scale)and Analysismodes. The ADS1x31REF switches modes onlywhen itisdisplayingdata.Iftheswitchischanged ina configurationmode, nothinghappens untiltheconfigurationmode isexited.AtthattimetheADS1x31REF readstheswitchand entersthe selectedmode. The fourbuttonshave differentfunctions,dependingon theoperatingmode. InScalemode, theswitches have thefunctionsinthebox labeledSCALE .InAnalysismode, theswitcheshave thefunctionsshown in thebox labeledANALYSIS .Inconfigurationmode, theswitcheshave thefunctionsshown inthebox labeledCONFIG . The buttonsalsohave differentnames indifferentmodes. Inthisdocument,theyareidentifedby the respectivenames theyhave inthemode underdiscussion.

1.2.1 AuxiliaryControls

The Resetswitchresetstheboard,exceptfortheUSB interface. The USB ResetswitchresetstheUSB interface.IfUSB communicationfails,pressingUSB Reset may solvetheproblem. The Programming Mode switchisused toupdatethefirmware.Fornormaloperation,itshouldbe setto JTAG.

1.3 Power

To applypower totheADS1x31REF, connecta 9V batteryorplugina 6V–9V ac walladapter. AC adaptersmust be tippositive/sleevenegative.When an ac adapterispluggedin,theboardalways takespower fromit,and notfromthebattery. The ADS1x31REF isprotectedagainstpolarityreversal.Ifa power sourceisconnectedinreverseby mistake,thedisplayremainsblank.To preventdamage totheboard,do notleavea reversedpower sourceconnectedforlongerthana few seconds.

1.4 Connecting a Load Cell

The ADS1x31REF isspecificallydesignedforconnectiontoloadcells.Two connectorsareprovidedfor thisapplication.The terminalblockisused forloadcellshavingstrippedwireconnections;theloadcell headerisforloadcellshavinga headerconnector.The terminalblockprovidesconnectionstothe referenceinput(orpower supply)and theheaderhas switchedexcitation.

1.4.1 Connecting a 4-WireLoad CelltotheTerminalBlock

Figure2 shows theconnectionofa 4-wireloadcelltotheterminalblock.Inthisconfiguration,theloadcell isexcitedby the+5V power supply,and theADC referenceistakenfromthepower supply. Forthisconfiguration,thereferenceselectswitchmust be inthe+5VA position. Figure2.4-WireLoad CelltoTerminalBlock

4 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

www.ti.com GettingStarted

1.4.2 Connecting a 6-WireLoad CelltotheTerminalBlock

Figure3 shows theconnectionofa 6-wireloadcelltotheterminalblock.Inthisconfiguration,theloadcell isexcitedby the+5V power supply,and theADC ’s referenceistakenfromthesense wirereturningfrom theloadcell.The sense wireconnectstotheexcitationwireatthebridgesensor. Figure3.6-WireLoad CelltoTerminalBlock

1.4.3 Connecting a 4-WireLoad CelltotheHeader

Figure4 shows theconnectionofa 4-wireloadcelltotheheader.Inthisconfiguration,theloadcellis excitedby the+5V power supply,and theADC referenceistakenfromthepower supply. Figure4.4-WireLoad CelltoHeader Forthisconfiguration,thereferenceselectswitchmust be inthe+5VA position;theEXT positiondoes not work.

1.4.4 Connecting a 6-WireLoad CelltotheHeader

Figure5 shows theconnectionofa 6-wireloadcelltotheheader.Inthisconfiguration,theloadcellis excitedby the+5V power supply,and theADC referenceistakenfromthesense wirereturningfromthe loadcell.The sense wireconnectstotheexcitationwireatthebridgesensor. Figure5.6-WireLoad CelltoHeader Forthisconfiguration,thereferenceselectswitchshouldbe intheEXT positionforbestperformance.The +5V positionalsoworks,butthedevicemay notperformas well. 5SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

GettingStarted www.ti.com

1.5 Connecting Other SignalSources

Ingeneral,theADS1x31REF can accuratelymeasure any voltageintheinputrangeoftheinstalledADS device,as longas thefollowingrulesareobserved:

Never applya negativevoltagetotheinputsoftheADS1x31REF. The installedADS devicecannot acceptnegativevoltagesatitsinput.Applyingnegativevoltagesmay damage boththedeviceand the ADS1x31REF. (Thenegativesignsused insome signalnames indicateinversion,notpolarity.)
Forsingle-endedsignals,groundthenegativeinputorconnectitto2.5V.2.5Visavailablefroma voltagedividerby shortingJ7;see Section6.4.5fordetails.
The inputrangeoftheamplifieron theADS1131 orADS1231 does notextendtothesupplies.See the ADS1131 datasheetortheADS1231 datasheetfordetails. Note thatScalemode isdesignedonlyforuse withloadcells.Althoughitcan be testedwitha voltage sourceorresistivedivider,Scalemode does not,ingeneral,displaymeaningfuldataunlessa loadcellis connectedand calibrationisperformed.

1.6 Connecting an ExternalClock

Note thatonlytheADS1231 can receivean externalclock.To connectan externalclock,connecta clock oscillatortotheEXTCLK testpoint.No settingsneed tobe changed;theADS1231 willautomaticallyuse theattachedclock. The clocksourcemust conformto3.3VTTL orCMOS logicrules.

1.7 Common Tasks

1.7.1 Shorted-InputNoise Test

The noisemeasurements givenintheproductdatasheetaretakenwiththeinputsshortedto2.5V.These noisemeasurements can be replicatedon theADS1x31REF withno externalhardware.To setup these measurements on theADS1x31REF, performthefollowingsteps: 1. Move themode switchtoAnalysismode. 2. ShortjumpersJ8 and J7.(Thesejumpersarelocatedveryneartheterminalblock,and aremarked InputShortingJumpers inFigure1.) 3. Setup theinstalledADS deviceas desired,as describedintheprevioussections. 4. Holddown theDISP button.The displayshows thecurrentdisplaymode. Whileholdingdown DISP, presstheMODE buttonuntiltheword on theleftsideisRMS. 5. Whilestillholdingdown DISP,presstheUNIT buttonuntiltheword on therightsideisVOLT. 6. ReleasetheDISP button.The displayshows theword GOTfollowedby an increasingnumber.Once theappropriatenumber ofpointsiscollected,thecalculatednoisevoltageisdisplayed.Thisvalueis theshorted-inputRMS noisevoltage,input-referred. The firstRMS noisemeasurement may be incorrectas a resultofdevicesettling.The second measurement isgenerallycorrect. Fora detaileddescriptionofAnalysismode, see Section3.

1.7.2 Measuring Mass

The followingitemsarerequiredtomeasure mass withtheADS1x31REF:

A loadcell,connectedas describedinSection1.4
An objectofknown mass withintheloadcellrange To avoidperformingcalibrationon each power-up,you can save thecalibrationsettingstoflashmemory. See Section3.4.1fordetails.

6 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

www.ti.com Weigh ScaleMode Obtaininga calibrationweight: BeforetheADS1x31REF can displaythemass ofan object,itmust measure theoutputoftheloadcellfor a previouslyknown mass. The known mass can be adjusted. Atpower-up,theADS1x31REF expectsa 5kg mass. Ifthismass isnotavailable,oriftheloadcellrange isnotcompatiblewiththismass, thecalibrationmass can be changed inthefollowingmanner: 1. Determinethemass ofthecalibrationweight.The most accurateway todeterminethemass isto weighthecalibrationobjecton an accuratelycalibratedscale.Iftheweightisprecalibrated,itsgiven mass can be used,althoughthisapproachisnotgenerallyas accurate.(Notethattheaccuracyofthe ADS1x31REF as a scaledirectlydepends on theaccuracytowhichthecalibrationweightcan be measured.) 2. Switchthemode switchtoSCALE mode. 3. PressthePARM buttonssimultaneously.The ADS1x31REF entersconfigurationmode. 4. Use thePARM buttonstoselectthescreenwhichshows UNIT=.Thisscreenallowsyou toselectthe unitsused forthecalibrationmass. Iftheunitsshown arenotcorrect,adjustthem usingtheVALUE buttons. 5. Use thePARM buttonstoselectthescreenthatshows CW=followedby thecalibrationmass. On this screen,you can adjusteach digitofthecalibrationmass separately.SelectthedigitusingthePARM buttons.The currently-selecteddigitflashes,and can be adjustedusingtheVALUE buttons. 6. Adjustthecalibrationmass tomatch themass ofthecalibrationweight. 7. PressthePARM buttonssimultaneouslytoexittheconfigurationmode. PreparingScalemode: Do thefollowingstepstosetup thescalemode: 1. Connecttheloadcell. 2. IftheinputshortingjumpersJ8 and J7 areconnected,disconnectthem (seeFigure1). 3. Obtaina weightofknown mass. 4. Ifthemass oftheweightisnotequaltotheconfiguredcalibrationmass, adjustthecalibrationmass as describedabove. 5. Move themode switchtoSCALE position.Ifcalibrationhas notbeen performed,thedisplayreads NOCAL. 6. PresstheCAL button,and followthecalibrationproceduregiveninSection2.3. Ifthecalibrationisperformedproperly,and theloadcellisconnectedcorrectly,theADS1x31REF will measure themass ofan objectplacedon theloadcell(providedthatthemass oftheobjectiswithinthe devicerange). Weigh scalemode isdescribedindetailinSection2.

2 Weigh ScaleMode

Inweighscalemode, theADS1x31REF displaysmass.(1) Mass isdisplayedineitherSIoravoirdupois unitsbased on thevoltagereceivedfroma loadcell. The ADS1x31REF operatesinScalemode when themode switchissettotheScaleposition. To accuratelycalculatemass, theADS1x31REF must have calibrationinformationfortheloadcell.When scalemode isfirstentered,theADS1x31REF displaysNOCAL,because theADS1x31REF has no calibrationdatawhen itispowered on. By default,mass iscalculatedfromtheaverageoffoursuccessivereadingsfromtheADC. The number of pointsforaveragingcan be adjusted,and averagingcan be turnedoff. (1) Load cellsdo notmeasure mass directly;theyoutputa voltageproportionaltotheweightofan object.The mass ofan objectcan be accuratelyinferredfromthisvoltageas longas a calibrationisaccuratelyperformed,thedownward forceofgravityremainsconstant(as itdoes iftheloadcellisnotmoved toa differentaltitude),and thetiltoftheloadcelldoes notchange;ifeitherofthelatterconditions change,a new calibrationmust be performed. 7SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

m□= wfs c/c45cfs zs Weigh ScaleMode www.ti.com

2.1 Display

Weigh scalemode can displaymass intheseunits:μg (displayedas ug),g,kg,pounds (lb),stone(st), and ounces (oz).(2) Internally,mass ismeasured ingrams,and calibrationfactorsarestoredingrams.Atdisplaytime,grams areconvertedtothedesireddisplayunitusingtheconversionfactorsgiveninTable1. xxx (2) The avoirdupoisunitsused by theADS1x31REF areequalintheimperialand U. S.customarysystems. Table1.UnitConversion Factorsand DisplayFormats Unit Multiplier Format micrograms(μg) 106 nnn.nnnug milligrams(mg) 1000 nnn.nnnmg grams (g) 1 nnn.nnng kilograms(kg) 10–3 nnn.nnnkg ounces (oz) 0.035274 nnn.nnnoz pounds (lb) 0.0022046 nnn.nnnlb stone(st) 157.473× 10−6 nnstnn.nn The displayformatforstonediffersfromtheformatused fortheotherunits.One stoneisequaltofourteen pounds;weightinstoneiscommonly expressedas a number ofstonefollowedby a number ofpounds. On theADS1x31REF, two digitsareshown forstone,followedby st,followedby pounds displayedtotwo decimalplaces.

2.1.1 CalculationofMass

Mass iscalculatedfromADC code usingtheformula: w = m ● c + w zs – w t where:

w = mass
c = theADC code
w t = tareweight
m, w zs,w t = valuesdeterminedinthecalibrationprocess m isa calibrationconstant,and iscalculatedusingEquation1: (1) where w fs istheuser-specifiedcalibrationmass, cfs istheADC code takenwiththecalibrationmass applied,and czs istheADC measurement takenwithno load. w zs ,thezero-scalemass, iscalculatedfromm and czs usingEquation2: w zs = –m ● czs (2)

2.2 Button Functions

2.2.1 TARE

The tarefunctionallowsthemass ofa substancetobe measured separatelyfromthemass ofits container.When theTARE buttonispressed,thescalemeasures themass and recordsit.Thisreadingis subtractedfromeach subsequentmeasurement. The recordedtarevaluecan be resettozeroby holdingtheTARE buttondown foratleastone second. When thetarevalueistobe reset,thedisplayreadsTAREOFF. Tareisalsoresetfollowinga calibration.

8 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

www.ti.com Weigh ScaleMode

2.2.2 RANGE

The RANGE buttonchanges theunitsorrangeofthedisplay.RANGE cyclesthroughallavailableunits; see Section2.1fordetails.When theRANGE buttonisdepressed,itdisplaystheselectedunit.

2.2.3 CAL

PressingCAL initiatesthetwo-pointcalibrationsequence.See Section2.3fordetails.

2.3 Calibration

Two-pointcalibrationisperformedby pressingtheCAL button.When thisbuttonispressed,theboard executesthefollowingcommand sequence: 1. The boardscrollsthemessage, REMOVEWEIGHT. 2. The userremoves allweightfromtheloadcelland pressesany button. 3. The boardmeasures theloadcellvoltageand recordsitas thezeropoint. 4. The boardscrollsthemessage PLACECALWEIGHT. 5. The userplacesa weighton theloadcelland pressesany button.The weightshouldhave themass thatwas selectedintheconfigurationmode. 6. The boardmeasures theloadcellvoltageand recordsitas thecalibrationweight. New calibrationdataislostwhen power isremoved.To preventthisdataloss,calibrationdatacan be saved,withotherboardsettings,toflashmemory. See Section3.4.1fordetails.

2.4 Configuration

The parametersforScalemode can be adjustedintheconfigurationmode. To enterconfigurationmode, pressthePARM buttonssimultaneously.The fourbuttonsthenassume the functionsshown intheCONFIG box.To exitConfigurationmode, pressthePARM buttonssimultaneously again.Thisfunctiondoes notcause parameterstobe adjusted,because onlybuttonreleasesaredetected inConfigurationmode. Configurationmode containsa number ofadjustableparameters.To scrollthroughtheavailable parameters,use thePARM buttons.To change theparametervalues,use theVALUE buttons. Some itemsinconfigurationmode arenotparameters,butcommands orgatewaystoa submenu. These itemsarelabelledas words witha questionmark.To entertheseortoexecutethecommand, pressSEL orENT . Allparametersintheanalysisand scaleconfigurationmenus areindependent,includingtheparameters foundinbothmodes. Table2 summarizestheavailableparameters. Table2.Parameters inConfigurationMode Parameter Display Value Range Description Displayunits UNIT= μg,mg, g,kg,lb,st,oz Displayunits Averages AVGS= 2–128 Number ofpointsto average ADC speed SPD= FAST, SLOW Acquisitionrate Calibrationmass CW= 0–99.9invariousunits Calibrationmass and unit Save parameters SAVE? — Save parameters;see text Versionnumber V1.0.0 — Firmwareversionnumber display 9SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

Weigh ScaleMode www.ti.com

2.4.1 Parameters

Displayunits:The unitstouse when displayingmass. Availableunitsareμg (displayedas ug),mg, g,kg, ounces (oz),pounds,(lb),and stone(st).See Section2.1fordetails. Averages:Number ofpointstouse when readingweight.The choicesavailableare2,4,8,10,16,32, 50,64,100,and 128.The defaultis50. ADC speed: Thisparameterselectsbetween thetwo datarateson theinstalledADS device,whichare calledhigh-speedand low-speed.When high-speedmode isselected,FASTisshown;forlow-speed mode, SLOWisshown.(1) The actualdatarateoftheADS1131 orADS1231 depends on thefrequencyofthemasterclock,fCLK .In fastmode, thedatarateisfCLK /61440;inslowmode, thedatarateisfCLK /491520.See theADS1131 data sheetortheADS1231 datasheetforfurtherinformation. The defaultsettingislow-speedmode. Calibrationweight:Thisparametergivestheexpectedmass ofthecalibrationweightused inthe calibrationprocedure(Section2.3).The calibrationmass can be giveninany oftheavailableunits,in threesignificantfigures.The unitisindependentofthedisplayunit. Each digitinthemass isadjustedseparately.The currently-selecteddigitflashes,and can be adjusted withtheVALUE buttons.The PARM buttonsareused toselectthedigit.The unitisadjustedinthesame manner,and flasheswhen selected. When theunitischanged,thevaluechanges totheequivalentmass inthenew unit. Save parameters:ThisscreenallowsthesettingsoftheADS1x31REF tobe storedinflashmemory. It functionsthesame as itdoes inAnalysismode. When ENT orSEL ispressedon thisscreen,the ADS1x31REF savesitssettingstoflashmemory. These settingsareloadedfromflashmemory when the boardisresetorpowered on.Alloperatingparametersaresaved,includingscalecalibrationsettings, voltagereference,displaymode, and units. Versionnumber: Thisscreendisplaystheversionnumber oftheADS1x31REF firmware. (1) The ADS1x31REF cannotdetectthefrequencyoftheADS1231 masterclock,so itcannotdisplaytheactualdatarateoftheADS1231 device.

10 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

www.ti.com AnalysisMode

3 AnalysisMode

InAnalysismode, theADS1x31REF analyzescode outputfromtheinstalledADS deviceand displaysitin differentways.Table3 summarizesthenumerous displaymodes available,togetherwithexample displays. NOTE: The valuesshown inTable3 areconsistentfora 24-bitdevice,such as theADS1231. However,theADS1131 isan 18-bitdevice,so theactualnumber ofcodes willbe fewerthan theexamplesshown here. Table3.Modes and Example Displays Hex Code Dec Code Voltage ENOB Raw 1992E9H +1676001 +499.488M n/a RMS n/a +5.789 +17.495N +23.18BIT Peak-to-Peak n/a +31.256 +90.293N +21.92BIT Averaged n/a +1676001 +499.488M n/a The ADS1x31REF operatesinAnalysismode when themode switchissettotheANALYSIS position. The defaultAnalysismode isRAW HEX. To change measurement types,holddown DISP and pressMODE .Thisfunctioncyclesthroughthefour availablemeasurement types.When DISP isreleased,thenewlyselectedmeasurement ismade. To change units,pressUNIT.Thisoptioncyclesthroughtheavailableunitsfortheactivemeasurement type. Thisprocedurecan alsobe done whileDISP isdepressed;inthatcase,thenew unitisshown by name on thedisplay.The measurement modes aredescribedindetailinSection3.2. The ADS1131 orADS1231 itselfcan be configureddirectlyfromthismode, as describedinSection3.1.

3.1 Switch Functions

NEW BLOCK: PressingthisswitchresetsthecollectionprocessfortheRMS, peak-to-peak,and averagedmeasurements. UNIT: Cyclesbetween availableunits.Not allunitsareavailableinallmodes. DISP: When thisswitchispressed,thedisplayshows thecurrentmeasurement mode and unit.While DISP isstillpressed,pressingNEW BLOCK /MODE cyclesthroughtheavailablemeasurement modes. CHIP: Holdingthisswitchdown allowsthesettingsoftheinstalledADS devicetobe changed,usingthe PARM (NEW BLOCK) and VAL (UNIT)buttons. PressingPARM whileCHIP ispresseddown cyclesthroughtheavailableparametersofgainand data rate. The gainsettingisdisplayedas GAIN=followedby thegainsetting.The gainsettingisfordisplayonly, because thegainisfixedat64 fortheADS1131 and 128 fortheADS1231. Data rateisshown on thedisplayas SPD=FASTorSPD=SLOW.See ADC speed intheParameterssection forfurtherinformation. Ifany oftheseparametersarechanged duringa multisamplemeasurement,themeasurement is restarted. 11SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

v = B 1/c45 x vREF A /c183 s =N (x )/c45i x i =1 N /c229 E = N log s :/c45 2 N 0sN /c185 24 : s 0N /c61 AnalysisMode www.ti.com

3.2 Measurement Modes

Raw: Inthismeasurement,codes arereadfromtheinstalledADS deviceand displayed.No processingor analysisisdone on thesample stream.Data can be displayedas hexadecimalcodes,decimalcodes,or volts. VoltageiscalculatedaccordingtoEquation3: Where:

A istheconvertergain(64fortheADS1131 and 128 fortheADS1231)
vREF isthevoltageattheconverterreferenceinput
x istheADC decimalcode
B isthenumber ofconverterbits,218 fortheADS1131 and 224 fortheADS1231 (3) vREF isadjustablefromConfigurationmode. By default,itis5V. The voltagedisplayisautoranging.Allrangesareshown withsixsignificantfigureshavingthreedecimal places.The rangesaregiveninTable4. Table4.VoltageDisplayRanges VOLTAGE RANGE DISPLAY SUFFIX Nanovolts < 1μV n Microvolts < 1mV u Millivolts < 1V m Volts ≥ 1V V RMS noise:Inthismode, a number ofcodes arereadfromtheinstalledADS device,and an RMS noise calculationisperformedon them usingthestandard-deviationformula(giveninEquation4): (4) The resultcan be displayedas decimalcodes,volts,oran effectivenumber ofbits(ENOB). Fordecimal codes,sN isdisplayeddirectly.(Hexadecimalisnotavailablebecause sN may be fractional.)Forvolts,sN isconvertedtoa voltageas inraw mode. ENOB: E iscalculatedusingEquation5: (5) Where N isthemaximum number ofavailablebits(18fortheADS1131 and 24 fortheADS1231). The zerocase isneeded when a stringofequalcodes isread.Thiscan happen when theconverteris clipping. Thismeasurement requiresa number ofcodes tobe readbeforea calculationcan be made. Therefore, duringthefirstrun,thedisplayshows theword GOTfollowedby thenumber ofsamplescollected.This eventhappens when themode isfirstentered,when theconverterconfigurationchanges,orwhen NEW BLOCK ispressed. The number ofcodes used inthecalculationisselectedinConfigurationmode; 50 codes areused in laboratorycharacterization,so thisvalueisthedefault. Peak-to-peaknoise:Inthismode, a number ofcodes arecollected,and theabsolutevalueofthe differencebetween theminimum and maximum iscalculated.The resultcan be displayedindecimalor hexadecimalcodes,volts,ornoise-freebits(ENOB). Voltsarecalculatedas inraw mode; ENOB is calculatedinthesame way as inRMS mode.

12 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

www.ti.com AnalysisMode The number ofcodes used inthecalculationisselectableinConfigurationmode. Averaged: Inthismode, a number ofcodes arecollected,and theaverageiscalculated.The resultcan be displayedindecimalcodes orvolts.(Hexadecimalisnotavailablebecause theresultmay be fractional.)Voltsarecalculatedas inraw mode. The number ofcodes used inthecalculationisselectableinConfigurationmode.

3.3 Progress Graph

The row ofapostrophesatthetopofthedisplayareused toindicatemeasurement progress.InRaw mode, theapostrophemoves acrossthedisplaywhen dataisbeingreceivedfromtheconverter. Inblockcollectionmodes, theapostrophesforma bargraph.As thecollectionofa blockproceeds,the bargraphincreases.When thebargraphreachesalltheway totheright,thenew resultisgeneratedand collectionrestarts.

3.4 Configuration

To enterConfigurationmode, pressthePARM buttonssimultaneously.The fourbuttonsthenassume the functionsshown intheCONFIG box.To exitConfigurationmode, pressthePARM buttonssimultaneously again.Thisoperationdoes notcause parameterstobe adjusted;onlybuttonreleasesaredetectedin Configurationmode. Configurationmode containsa number ofadjustableparameters.To scrollthroughtheavailable parameters,use thePARM buttons.To change theparametervalues,use theVALUE buttons. Some itemsinconfigurationmode arenotparameters,butcommands orgatewaystoa submenu. These itemsarelabelledas words witha questionmark.To entertheseitemsortoexecutethecommand, press SEL orENT . Althougha few oftheparametersintheAnalysisand Scaleconfigurationmenus arethesame, the settingsarekeptseparatebetween themodes. Table5 summarizestheavailableparameters. Table5.Parameters inAnalysisMode Parameter Display Value Range Description Averages AVG= 2–128 Number ofpointsforaverage, peak-to-peak,and RMS modes VoltageReference VREF= 0.5–5.0 Voltageused invarious calculations Power-down mode PDWN? — Power-down mode; see text Save parameters SAVE? — Save parameters;see text Versionnumber V1.0.0 — Firmwareversionnumber display

3.4.1 Parameters

Averages:Number ofpointstouse inAveraged,RMS noise,and Peak-Peak calculations.The choices availableare2,4,8,10,16,32,50,64,and 128.The defaultsettingis50. Voltagereference:To convertvoltagestocodes,theADS1x31REF requiresthevoltagereferencelevel. Sincethislevelcannotbe measured,itmust be selectedmanually.Thisparameterallowsthereference leveltobe set. Each digitofthevoltagereferenceisselectedand adjustedseparately.Use thePARM buttonstoselecta digit,and theVALUE buttonstoadjustit.The selecteddigitflashes. Thisparameterdoes notaffecttheactualvoltagereferenceused.Ifitisincorrect,voltagecalculationswill be wrong.The voltagereferenceistypicallythe+5V rail;thedefaultvalueforthisparameteris5.0V. 13SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

UsingthePC Software www.ti.com Power-down mode: When ENT orSEL ispressedon thisscreen,theADS1x31REF causestheinstalled ADS devicetoenterpower-down mode. Thisactionoccursby pullingthePDWN linelow.Whilethe PDWN lineislow,thedisplayreadsPOWER DN. When a buttonispressedfromthisdisplay,the ADS1x31REF powers theconverteron and returnstotheanalysisdisplay,exitingconfigurationmode. Thismode can be used totestthecurrentconsumptionoftheboardwhen theinstalledADS deviceis powered down. Versionnumber: Thisscreendisplaystheversionnumber oftheADS1x31REF firmware.

4 Using thePC Software

The ADS1x31REF issuppliedwithsoftwarethatperformsvariousanalyseson datareceivedfromthe boardviatheUSB connection.Italsoprovidesa means ofrecordingreceiveddatatoa file. The programcurrentlyrunsonlyon a MicrosoftWindows ® platform.InWindows, theprogram communicateswiththeADS1x31REF usinga virtualCOM portdriverthatcausestheUSB connectionto appeartoWindows as a normalserialport.The necessarydriverisinstalledwiththeEVM software.

4.1 Installationand Setup

The ADS1x31REF softwareisdistributedinan installerprogramcalled ADS1x3x-setup-withLVRT-1.3.0.exe(theversionnumber inthefilename may differ),distributedon the CD-ROM oravailablefromTexas Instruments.To installthesoftware,executethisprogram.The program guidesyou throughtheinstallationprocess. Note thefollowingpoints:

The installerinstallstwo packages:theADS1x3xREF programitself,and theTIVirtualCOM Port driver.
Ifany versionoftheADS1x3xREF programisalreadyinstalled,theinstalleruninstallsitand quits.You must runtheinstalleragaintocompletetheinstallation.
IftheVirtualCOM Portdriverisalreadyinstalled,theinstallerofferstouninstallit.Do not uninstallit; cancelthispartoftheinstallation. The installerdisplaysmessages remindingyou ofthesepoints.

4.1.1 FirstTime Connection oftheADS1x3xREF

IftheADS1x31REF has neverbeen connectedtoyourcomputerbefore,Windows detectsthedeviceas unknown hardwareand takesyou througha seriesofdialogstoinstallthecorrectdriver.Acceptthe defaultsettings;thedriverispresentand onlyneeds tobe copiedtothecorrectlocation.Ifthedriveris successfullyinstalled,Windows does notissuethispromptagain. On some computers,iftheboardisconnectedtoa differentUSB port,theoperatingsystemdetectsthe boardas new hardware.Ifthisactionoccurs,proceedthroughthenew hardwaredialogsas usual,and allowWindows toreinstallthedriver.

4.2 The Display

The ADS1x31REF softwarehas a singledisplay;see Figure6 fora typicaldisplay.The majorelementsof thedisplaydiscussednext. Stripchart:Thisfeaturedisplaysa scrollinggraphofdatareceivedfromtheboard. Histogram:A slidinghistogramofdatareceivedfromtheboardisalsodisplayed.The number ofpoints used intheanalysisisadjustable. DC analysissection:The resultsofRMS noiseanalysis,peak-to-peakanalysis,and a runningvoltage number areshown inthissection.The number ofanalysispointsand thereferencevoltageused for voltagecalculationsarealsoadjustablehere. Recording section:Thisfeaturecontrolsrecordingofdatatoa file. Device controlsection:Thissectionallowsdeviceparameterstobe adjusted.

14 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

www.ti.com UsingthePC Software Statusdisplay:Thisdisplayshows messages indicatingthecurrentstateoftheprogram. Acquirebutton:Thisbuttonstartsand stopstherunningacquisitionofdata.

4.3 StartingtheProgram

When theprogramlaunches,a screensimilartothatshown inFigure6 appears.Immediatelyafterlaunch, theprogramsearchesallavailableserialportsfortheboard.To do thisstep,itopens everyavailable serialportinturn,testingittosee ifthereisan ADS1x31REF connected.The programuses thefirst ADS1x31REF itfinds.Note thatthetitleblockdisplaysthename oftheboardfound.Figure6 shows the boardfoundas theADS1231REF .IftheADS1131REF isconnected,thetitleshows ADS1131REF . Figure6.ADS1231REF PC SoftwareDisplay Althoughthisprocedureisconceptuallysimple,itmay notgo as smoothlyas expected.The following processensuresthattheboardisfoundcorrectly.Note thatSteps1–3 can be done inany order. Step1. Applypower totheADS1x31REF. Step2. PlugintheUSB connector. Step3. Starttheprogram. Step4. Watch thestatusdisplay.ItreadsScanningfollowedby thename oftheserialportbeing tested.When theboardisfound,thedisplayreadsIdle.Untila boardisfound,thedisplay cyclesthrougheveryport,spendingapproximatelyone second on each port. Once theboardisdetected,theprogramentersIdlemode and isreadyforuse. NOTE: Iftheboardisneverdetected,itisstillpossible(andsafe)toexittheprogramduringthe searchprocess.Iftheboarddoes notrespond,pressingtheUSB Resetswitch(SW1) may help. 15SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

Strip□Chart UsingthePC Software www.ti.com

4.4 Analysisor Record Mode

The programwilloperateinanalysismode orrecordmode. Bothmodes acquirethedataand updatethe displays,butrecordmode alsowritestheresulttotheselectedfile.

4.5 AdjustingDevice Parameters

To adjustdeviceparameters,use thecontrolsintheDevicecontrolbox.Each controlcorrespondstoa settingthatcan alsobe made fromtheboarditself.

4.6 AcquiringData

To startreceivingand analyzingdatafromtheboard,clicktheAcquirebutton,locatedinthelower right-handcornerofthedisplay.The programbeginstoreceivedatafromtheboard,displayingtheresults innear-realtime. ItisnotpossiblefortheprogramtoadjustboardparametersinAnalysismode. Forthisreason,theboard controlsaredisabledand dimmed whileAnalysisoccurs.

4.6.1 Averaging

The PC softwarecan processdatacollectedfromtheboardusinga sliding-windowaverager.The controls fortheaveragerarefoundintheAveragerbox. To turntheaverageron,use theAveraging switch.The number ofpointsaveragedissetby thePoints control,and thenumber ofpointscurrentlycollectedisshown intheCollectedbox. When theaverageristurnedon,itiscleared.To resettheaverager,turnitoffand thenon again. The histogramdisplaysan integerrepresentationoftheaverageddata.Note thatwhen selectinga high number ofaverages,theintegerresultsmightincludeonlyone code;thehistogramforthatcase willbe blank.The stripchartdisplayshows boththefullprecisionresultoftheaveragesand theintegerversion, as illustratedinFigure7. Figure7.ADS1x31REF Average Data

16 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

www.ti.com UsingthePC Software

4.6.2 Block AnalysisLength

The histogram,RMS, and peak-to-peakcalculationsrequirea setofsamples.These calculationsare updatedwitheverygroupofsamplesreceived,and areperformedon a blockofthemost recently acquired(oraveraged)samples. The number ofsamplesused issetusingtheAnalysispointscontrol.By default,thisnumber is100,but can be changed atany time.ThisvaluealsocontrolstheRMS and peak-to-peaknoiseanalysislengths. Ifthenumber ofsamplescollectedisnotyetequaltothenumber ofsamplesspecifiedby theAnalysis pointscontrol,0s aresubstitutedforthesamplesnotyetreceived. InAnalysismode, theanalysiscan be resetusingthebuttonmarked Resetanalysis.Thisfunctionclears theinternalanalysisbuffer.Thisbuttoncannotbe used outsideofAnalysisand Recordingmodes. Analysisisautomaticallyresetwhen Analysisand Recordingmodes areentered.

4.6.3 RMS and Peak-to-PeakNoise Analysis

The RMS and peak-to-peaknoiseanalysiscalculationsareperformedinexactlythesame way as theyare intheADS1x31REF firmware,as describedinSection3.2.Each calculationcan be displayedinunitsof volts,codes,orbits,as on theboard.See Section3.2fordetaileddescriptionsofthecalculations. The number ofsamplesused ineach calculationissetusingtheAnalysispointscontrol.By default,this number is100,butcan be changed atany time.Thiscontrolalsocontrolsthehistogramlength.

4.6.4 DisplayingVolts

When unitsofvoltsaredisplayed,theprogrammust have a valueforthereferencevoltageappliedtothe installedADS devicetoproperlycalculatethevoltage.Because thisvoltagecannotbe measured using theADS1x31REF, itissetmanuallyusingtheVrefcontrol. The valueofVrefdefaultsto5V,because thereferenceisnormallytakenfromthe5V power supply.Ifa differentreferencevoltagelevelisused,thevalueofVrefshouldbe changed toreflectthedifferentlevel, so thatvoltagecalculationsareperformedcorrectly. The VrefcontrolalsoaffectsvoltagesrecordedinRecord mode.

4.6.5 Block Acquisition

To enabletheprogramtorunreliablyon slowercomputers,resultsarenotcalculatedeach timea sample isreceived.Instead,groupsofsamplesarecollectedand added toan analysisbufferthatisprocessedas itbecomes full.Thisprocessingdelayistimedso thatthedisplayupdatesatleastevery0.75seconds.

4.7 Data Recording

The ADS1x31REF softwarecan recordincomingsamplestoa textfile.Thisfilecan be loadedintoother programsforanalysis.Data recordingisperformedusingthecontrolsintheRecordingbox. Followthesestepstorecorddatatoa file: Step1. Selectorcreatea destinationfile.EithertypethefilepathdirectlyintotheDestinationfile control,orclickthesmallopen foldericontotherightofthecontroltoopen a dialogbox from whicha filecan be selected.Iftheselectedfileexistsalready,theprogramwilldisplaya warning.Otherwise,typethename ofthefilethatyou wishtocreate. Step2. Selecta dataformat.Samples can be recordedas raw (decimal)codes oras volts.Inboth cases,thedataarewrittentothefileas ASCIIdata,and thefileisa textfile. Step3. ClicktheRecord button.The programbeginstocollectand analyzedatafromtheboard,as wellas writeittotheselectedfile.As recordingproceeds,therecordingtimeindicatorsare updated. Step4. ClickRecord againtostoptherecordingwhen thedesiredamount ofdatahas been collected. The selectedfileisnotopened orcreateduntilrecordingbegins.Ifan erroroccursatthattime,recording stopsand a message displaysinthestatusbox. 17SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

SerialConsole www.ti.com Recordingtimeisnotmeasured,butcalculatedfromthenumber ofsamplescollected.The speed isused todeterminetheamount oftimeforeach sample.Ifthedatarateischanged attheboard,therecording timewillbe incorrect.Thischange does notaffectthedatafile,exceptthatsamplescontinuetobe collectedwiththedifferentsettings. InRecordingmode, analysisproceedsas inAnalysismode; Recordingmode isidenticaltoAnalysis mode, exceptthatdataiswrittentoa file.See theprevioussectionfordocumentationon Analysismode. When Recordingmode begins,iftheselectedfileexists,itiserasedand overwritten.The pre-existenceof thefileischeckedonlywhen a new fileisselected.

4.7.1 FileFormat

Data filesbeginwitha headerthatcontainsthetextcollectedfromADS1x31REF ,thetimeofrecording, and thespeed and gain.Followingthisheader,valuesarewrittenineithervoltsorraw codes,withone valueperline.LineseparatorsareinDOS format,consistingofa carriagereturnand a linefeed.This formatcan be examined ina texteditorand loadedorimportedintomost othersoftware,including spreadsheets. VoltagesarecalculatedusingthereferencevoltagegivenintheVrefcontrol;itisthereforeimportantthat thisvaluebe correct.

5 SerialConsole

The ADS1x31REF providesa consolemode thatcan be used withany Windows terminalemulation program,such as Hyperterm™.InWindows, thisconfigurationisdone throughtheVirtualCOM Portdriver suppliedwiththeEVM software,causingtheADS1x31REF toappearinWindows as an extraserialport.

5.1 Using theConsole

To use theconsole,loada terminalemulationprogramand connecttotheEVM serialportusingthe followingparameters:

Baud rate:115200
Data bits:8
Parity:none
Stopbits:1
Flow control:none
Localecho:off
Terminalemulation:ANSI orVT100 Settingup theterminalprogramisbeyond thescope ofthisdocument;see thespecificterminalprogram documentationfordetails. To locatetheserialport,tryhigherportnumbers first.When theboardfirststarts,itoutputsthefollowing message: ADS1131REF1.0.0(c)2010TexasInstruments 1131> fortheADS1131, or: ADS1231REF1.0.0(c)2010TexasInstruments 1231> fortheADS1231. PressingReset causestheboardtooutputthismessage. The command promptisalways1131>fortheADS1131 and 1231>fortheADS1231. Commands are enteredatthisprompt.Commands consistofone letterpossiblyfollowedby arguments.The formatofthe argumentsdepends on thecommand. Commands arecase insensitive.Upper-casecharactersareprintedhere,butlower-casecharactersalso work.

18 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

www.ti.com SerialConsole The availablecommands arelistedinTable6.Inthistable,valuesinbracketsindicatea rangeorlistof possiblecharacters.A dash (–)indicatesa range,and commas (,)indicatea list. Table6.Console Mode Commands COMMAND FORMAT OPERATION PrintsthecurrentgainP — setting R SetdatarateR[F,S] V Show firmwareversionV S StartstreamingS D Read dataonceD Q Query parametersQ Consolemode does notinterruptstandaloneoperation.Itisalwaysavailable,even when thestandalone mode isinuse.However,ifparametersarechanged usingboththeconsoleand standalonemodes, parametersmay become outofsync.

5.2 Command Reference

5.2.1 P—Set PGA

Thiscommand has no effecton theADS1131 orADS1231 because thedevicegainisfixed.

P—(withno argument)printsthecurrentgainsetting

5.2.2 R —Set Data Rate

Thiscommand setsthespeed oftheinstalledADS deviceaccordingtotheseparameters:

RF—setsratetofast
RS—setsratetoslow
R—(withno argument)printsthecurrentdataratesetting Note thattheactualdataratedepends on thefrequencyofthedeviceclock.

5.2.3 V—Show Version

Displaysa message containingthefirmwareversionand copyrightnotice. 19SBAU175A –July2010–RevisedAugust2011 ADS1131REF and ADS1231REF SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

+5V +3.3V CH1 SPI GPIO UART Hardware www.ti.com

5.2.4 S—StartStreaming

When S isissued,theADS1x31REF beginsprintingraw outputcodes fromtheinstalledADS devicein hexadecimalformat,separatedby new lines.The deviceiteratescontinuouslyuntila characterisreceived fromtheserialport. S isused primarilyby theEVM softwarefordatacollection.

5.2.5 D —CollectOne Sample

IssuingtheD command causestheADS1x31REF toreportthelatestcollectedsample fromtheinstalled ADS device.The sample isdisplayedinraw hexadecimal.

5.2.6 C —Set Channel

Thiscommand has no effecton theinstalledADS devicebecause thereisonlyone channel.

C0 —settochannel0
C —(withno arguments)printsthecurrentchannel,alwaysCHAN=0

5.2.7 Q —Query Parameters

Q causestheADS1x31REF toissuea coded stringsummarizingthecurrentsettings.The formatofthe stringis: P0R[F,S]OIC0 followedby a carriage-returnand linefeed.

6 Hardware

A blockdiagramoftheADS1x31REF isshown inFigure8.The schematicand layoutdrawingsaregiven inAppendixA. Figure8.ADS1x31REF Hardware Block Diagram

20 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

www.ti.com Hardware

6.1 Microcontroller

The ADS1x31REF uses theMSP430F449 microcontroller.Thisdeviceprovidesan LCD controller, hardwareSPI and UART interfaces,and a multiplier.The latterisimportantbecause thefirmwaremust performmany multiplications.

6.2 Power Supply

The ADS1x31REF operatesfrom+5VDC and +3.3VDC. These suppliesaregeneratedby linearregulators U1 and U2. Inputpower comes fromeitherwall-adapterconnectorJ2,orbatteryconnectorBT1. J2 is switched;when a connectorispluggedin,BT1 isdisconnected. Noiseisimportantbecause theADC voltagereferenceistypicallytakenfromthepower supply.The suppliesareheavilybypassedtoreducenoise.

6.3 User Interface

The ADS1x31REF userinterfaceconsistsofthedisplayand switchesSW2 –5 and SW8. Switchesare connectedtointerrupt-capableGPIOs on themicrocontroller,allowingthem towake themicrocontroller fromsleepmode.

6.4 ADC Section

The ADC sectionconsistsoftheinstalledADS deviceitselfand ancillarycircuitry. Allsignalson theinstalledADS devicearefilteredby pass-throughcapacitorsthathelptoreject electromagneticinterference(EMI),radiofrequencyinterference(RFI),and noisegeneratedby thedigital circuitry.

6.4.1 InputCircuitry

The ADS1x31REF isdesignedtoconnecttoresistivebridgesensors,particularlyloadcells.The input channelisfilteredby pass-throughcapacitorsC38 and C39 and differentialcapacitorC7. Common-mode capacitorsC32 and C29 provideadditionalRF rejection.

6.4.2 Load CellHeader

The loadcellheader,J6,providesa convenientterminalforloadcellshavinga properlyfittedheader connector.Itprovidesexcitationand sense connections.The negativeexcitationlineisconnectedto groundthroughtheinstalledADS device.The ADS deviceconservespower by allowingexcitationcurrent toflowonlyduringconversion.See theADS1131 datasheetortheADS1231 datasheetformore information. The loadcellconnector’s pinoutisgiveninTable7.Forconnectionexamples,see Section1.4.3and Section1.4.4. Table7.Load CellHeader Pinout PIN NO. PIN NAME FUNCTION

1 EXC+ Positiveexcitation;connectedto+5VA

2 EXCSNS+ Positivesense;connectedtoexternalpositivereferenceinput

3 SIG+ Inputforpositiveloadcelloutput

4 SIG– Inputfornegativeloadcelloutput

5 EXCSNS – Negativesense;connectedtoexternalnegativereferenceinput

6 EXC – Negativeexcitation;connectedtogroundthroughinstalledADS

Hardware www.ti.com

6.4.3 InputTerminalBlock

The inputterminalblockconsistsofJ4 and J5.Itprovidesconnectionstoalloftheanaloginputson the installedADS device,and connectionstotheADS1x31REF voltagereferencenetwork. The terminalblockpinoutisgiveninTable8. Table8.TerminalBlock Pinout TERMINAL NAME FUNCTION NegativeexcitationconnectedtogroundEXC – throughinstalledADS device SNS – Invertingexcitationsense input SNS+ Noninvertingexcitationsense input SIG+ Noninvertinginput SIG– Invertinginput Positiveexcitationoutput(+5V)orpositiveEXC+ referenceinput

6.4.4 VoltageReference

The ADS1x31REF isdesignedtooperateeitherratiometricallyorwithan externalreference.The two modes areselectedusingswitchSW7. IntheEXT position,theinstalledADS referenceinputsaretakenfromtheloadcellconnectors.Inthe +5VA position,theinstalledADS positivereferenceinputcomes fromthe5V analogsupply,and the negativereferenceinputisconnectedtoground. Aftertheswitchisplaceda filteringnetworkthatconsistsofresistorsR14 and R15, bulkcapacitorC4, pass-throughcapacitorsC44 and C45, and filteringcapacitorsC28, C30, and C31.

6.4.5 InputShortingJumpers

The shorted-inputnoisetestfortheADS1x31 devicesisbestperformedwithbothinputsconnectedto 2.5V.To make thistesteasy toperform,jumpersJ7 and J8 areprovided. Jumper J8 shortstheinputstogether.Jumper J7 connectstheinvertinginputtoa voltagedividermade fromR25 and R26, dividingthepower supplyby 2.Thisvoltagedividerelectricallyresemblesan ideal bridgesensor.

6.5 USB Interface

The USB interfacecan be used forfirmwaredownloadordatacommunications.Itsroleinfirmware downloadisdiscussedinSection6.6. The USB interfaceconsistsofUSB-to-serialconverterU4, a Texas InstrumentsTUSB3410 .Thisdevice incorporatesa USB interfacemodule,a microcontroller,and a 16550-typeUART. Driversoftwareis availablethatcausesthedevicetoappearas a serialporton thehostPC. The USB interfaceispowered separatelyfromtherestoftheADS1x31REF; ittakespower fromtheUSB line,throughlinearregulatorU3. The serialportsideofU4 isconnectedtothemicrocontrollerUART signals.To keep thepower domains separate,and tokeep theUSB and microcontrollersidesfrominadvertentlypoweringeach other,the UART isconnectedthroughisolatorsU8 and U9.

6.6 Programming Connections

The MSP430 can be programmed viathededicatedJTAG portortheserialbootstraploader. The JTAG connectorisnotfactory-installed.The footprintissimilartoan edge-cardpattern,and acceptsa standarddual-row0.100inheadermounted on thesideoftheboard.Thisheaderiscompatiblewith MSP430 parallel-portJTAG adaptors.

22 ADS1131REF and ADS1231REF SBAU175A –July2010–RevisedAugust2011

www.ti.com AppendixA To allowfirmwaretobe downloadedthroughUSB, U4 isconnectedtothemicrocontrollerbootstraploader pins.The DTR and RTS pinsareconnectedtotheRST and TCK inputson themicrocontrollertoallowthe serialbootstraploadertooperate.These linesarenotisolated;instead,theyareswitchedthroughSW9, whichalsoconnectsUSB groundand power tothemicrocontrollergroundand power.Normallythisswitch isopen;itisonlyswitchedon when firmwareistobe downloadedthroughUSB. Thisfeaturealsoprotects themicrocontrollerfromunknown stateson thesepinsatpower-up. Appendix A Schematic and Layout The printedcircuitboard (PCB) layoutsforthetopand bottomsidesoftheADS1x31REF are shown in Figure9 throughFigure12,respectively.SchematicsfortheADS1x31REF areshown inSectionA.3.The billofmaterialsisprovidedinTable9. A.1 BillofMaterials NOTE: Allcomponents shouldbe RoHS compliant.Some partnumbers may be eitherleadedor RoHS. Verifythatpurchasedcomponents areRoHS compliant. Table9.ADS1x31REF BillofMaterials Item No ADS1131 ADS1231 Value Ref Des Description Vendor PartNumber 1 1 1 BT1 (+) 9 VoltBatteryClipFemale Keystone 594 Electronics 2 1 1 BT1 (–) 9 VoltBatteryClipMale Keystone 593 Electronics 3 4 4 22pF C1, C2, C16, 50V CeramicChipCapacitor,±5%, TDK C1608C0G1H220J C17 C0G 4 4 4 100pF C29, C30, 16V PPS FilmChipCapacitor,2% Panasonic ECH-U1C101GX5 C31, C32 5 4 4 100pF C40, C41, FilterHighFrequency,100pF Murata NFM21CC101U1H3D C42, C43 6 5 5 0.01μF C5, C11, 50V CeramicChipCapacitor,±10%, TDK C1608X7R1H103K C13, C14, X7R C15 7 6 6 0.1μF C12, C21, 50V CeramicChipCapacitor,±10%, TDK C1608X7R1H104K C33 toC36 X7R 8 2 2 0.1μF C6, C7 16V PPS FilmChipCapacitor,2% Panasonic ECH-U1C104GX5 9 3 3 1μF C9, C10, C22 16V CeramicChipCapacitor,±10%, TDK C1608X7R1C105K X7R 10 5 5 1μF C37, C38, FilterHighFrequency,1.0μF Murata NFM21PC105B1C3D C39, C44, C45 11 6 6 2.2μF C23 toC28 6.3VCeramicChipCapacitor,±20%, TDK C1608X5R0J225M X5R 12 1 1 4.7μF C3 16V CeramicChipCapacitor, TDK C2012Y5V1C475Z +80/–20%, Y5V 13 4 4 10μF C8, C18 to 16V CeramicChipCapacitor,± 20%, TDK C3216X7R1C106M C20 X7R 14 1 1 100μF C4 10V TantalumChipCapacitor,±10% Kemet T494D107K010AT 15 1 1 D1 30V,200mA SchottkyDiode Fairchild BAT54 Semiconductor 16 1 1 D2 Green LED, SMD Lumex SSL-LX3052GD 17 1 1 J1 USB Type 'B' Socket Mill-Max 897-43-004-90-000000 18 1 1 J2 2.5mm Power Jack CUI PJ-102BH 19 0 0 J3 2 X 7 Header 20 1 1 J6 1 X 6 Header Samtec TSW-106-07-G-S 21 2 2 J7,J8 1 X 2 Header Samtec TSW-102-07-G-S 22 1 1 J4 3.5mm PCB TerminalBlock,4 position On Shore ED555/4DS Technology 23SBAU175A –July2010–RevisedAugust2011 Schematicand Layout SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

BillofMaterials www.ti.com Table9.ADS1x31REF BillofMaterials(continued) Item No ADS1131 ADS1231 Value Ref Des Description Vendor PartNumber 23 1 1 J5 3.5mm PCB TerminalBlock,2 position On Shore ED555/2DS Technology 24 1 1 L1 FerriteBead Core,4A 100MHz Panasonic EXC-ML20A390U 25 1 1 LCD1 8 CharacterLCD Display,Reflective Varitronix VIM-878-DP-RC-S-LV Type 26 2 2 0Ω R23, R24 1/10W 5% ChipResistor Panasonic ERJ-3GEY0R00V 27 1 1 20Ω R17 1/4W 5% ChipResistor Panasonic ERJ-8GEYJ200V 28 2 2 33Ω R2, R3 1/10W 5% ChipResistor Panasonic ERJ-3GEYJ330V 29 4 4 100Ω R12 toR15 1/10W 5% ChipResistor Panasonic ERJ-3GEYJ101V 30 1 1 220Ω R11 1/10W 5% ChipResistor Panasonic ERJ-3GEYJ221V 31 1 1 1.5kΩ R1 1/10W 5% ChipResistor Panasonic ERJ-3GEYJ152V 32 8 8 10kΩ R4-R10,R16 1/10W 5% ChipResistor Panasonic ERJ-3GEYJ103V 33 2 2 20kΩ R25, R26 1/10W 1% ChipResistor Panasonic ERJ-3EKF2002V 34 2 2 47kΩ R18, R27 1/10W 5% ChipResistor Panasonic ERJ-3GEYJ473V 35 1 1 200kΩ R22 Potentiometer200K Ohm 1/4" SQ Bourns 3362U-1-204LF 36 3 3 221kΩ R19 toR21 1/10W 1% ChipResistor Panasonic ERJ-3EKF2213V 37 6 6 SW1 toSW6 PushbuttonSwitch ITT KSA1M211LFT 38 1 1 SW7 DPDT SlideSwitch,Top Actuator NKK SS22SDP2 39 1 1 SW8 SPDT SlideSwitch,Top Actuator NKK SS12SDP2 40 1 1 SW9 4PDT SlideSwitch,RA Actuator E-Switch EG4208 41 0 0 TP1 toTP14, Not Installed TP16 toTP18 42 1 1 TP15 Testpoint Keystone 5011 Electronics 43 1 0 U6 Two-ChannelAnalogtoDigital Texas InstrumentsADS1131ID Converter 0 1 Two-ChannelAnalogtoDigital Texas InstrumentsADS1231ID Converter 44 1 1 U5 MicrocontrollerwithLCD Drivers Texas InstrumentsMSP430F449IPZ 45 2 2 U2, U3 LinearVoltageRegulator,+3.3V Texas InstrumentsTPS77133DGK 46 1 1 U1 LinearVoltageRegulator,+5V Texas InstrumentsTPS76350DBV 47 1 1 U4 USB toSerialConverter Texas InstrumentsTUSB3410VF 48 2 2 U8, U9 DigitalIsolator Texas InstrumentsISO721D 49 2 2 U7, U10 Inverter,SingleGate Texas InstrumentsSN74LVC1G04DBVR 50 1 1 12MHz X1 QuartzCrystalSMD ECS Inc. ECS-120-20-23B-TR 51 1 1 32.678kHz X2 QuartzCrystal Epson C-002RX 32.7680K-E:PBFREE 52 1 1 N/A ADS1x31 REF PWB Texas Instruments6517107 53 4 4 N/A 1/4" x .75hex 4-40BrassThreaded Keystone 1656A Standoff Electronics 54 4 4 N/A PhillipsMachine Screw,1/2" 4-40 BuildingFasteners PMSSS 440 0050 PH 55 2 2 N/A ShortingBlock Samtec SNT-100-BK-G-H

24 Schematicand Layout SBAU175A –July2010–RevisedAugust2011

www.ti.com PCB Layout A.2 PCB Layout Figure9.ADS1x31REF PCB —Top Side Figure10.ADS1x31REF PCB —Layer 1 25SBAU175A –July2010–RevisedAugust2011 Schematicand Layout SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

PCB Layout www.ti.com Figure11.ADS1x31REF PCB —Layer 2 Figure12.ADS1x31REF PCB —Bottom Side

26 Schematicand Layout SBAU175A –July2010–RevisedAugust2011

2.2uF +3.3VD TP11 EXTCLK C43C40 +5VAC27 2.2uF C6 0.1uF C44 C45 R14 100 R15 100 C28 2.2uF C31 100pF C30 100pF C38 MUR_NFM21PC105F1C3D C39 MUR_NFM21PC105F1C3D R23 R24 0.1uF C29 100pF C32 100pF SW7 SW-DPDT +5VA +5VA DOUT SCLK SPEED PDWN TP13 VREF+ TP14 VREF- TP9 SCLK TP10 SPEED TP12 PWDN C41 C42 TP15 GND OST_ED555/4DS HEADER-6 +5VA EXC+ EXCSNS+ SIG+ SIG- EXCSNS- EXC- 100uF R26 20K R25 20K +5VA TP6 DOUT CUI-STACK PJ-102BH VIN1 VOUT 5 GND2 NR/ADJUST 4ENABLE3 TPS76350DBV BT1 10uF C11 0.01uF C19 10uF C20 10uF TP3 +5V TP4 +3.3VD +3.3VD +5V +5VA 1uF OST_ED555/2DS FB/SENSE 1 RESET 2EN3 GND4 IN5 IN6 OUT 7 OUT 8 TPS77133DGK RST R27 47K DVDD1 GND2 CLKIN3 SPEED4 CAP 5 CAP 6 AINP 7 AINN 8 VREFN 9VREFP 10 GND 11 AVDD 13 PSW 12 PDWN14 SCLK15 DRDY/DOUT16 ADS1231ID ADS1131ID (GND PIN 3) www.ti.com Schematics A.3 Schematics Figure13.ADS1x31REF Schematic—ADC 27SBAU175A –July2010–RevisedAugust2011 Schematicand Layout SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

P6.3/A3 P6.4/A4 P6.5/A5 P6.6/A6 P6.7/A7/SVSIN VREF+ XIN XOUT VeREF+ VREF-/VeREF- P2.4/UTXD0 P2.5/URXD0 P2.6/CAOUT P2.7/ADC12CLK P3.0/STE0 P3.1/SIMO0 P3.2/SOMI0 P3.3/UCLK0 P3.4/TB3 P3.5/TB4 P3.6/TB5 P3.7/TB6 P4.0/UTXD1 P4.1/URXD1 P4.2/STE1/S39 P4.3/SIMO1/S38 50 P4.4/SOMI1/S37 49 P4.5/UCLK1/S36 48 P4.6/S35 47 P4.7/S34 46 P5.0/S1 P5.1/S0 P5.2/COM1 P5.3/COM2 P5.4/COM3 P5.5/R13 P5.6/R23 P5.7/R33 XT2OUT88 XT2IN89 TDO/TDI90 TDI/TCLK91 TMS92 TCK93 RST/NMI94 P6.0/A095 P6.1/A196 P6.2/A297 AVSS98 DVSS199 AVCC100 S10 S11 S12 S13 S14 26S15 27S16 28S17 29S18 30S19 31S20 32S21 33S22 34S23 35S24 36S25 37S26 38S27 39S28 40S29 41S30 42S31 43S32 44S33 45 COM0 R03 DVCC2 DVSS2 MSP430F449IPZ R19 221K R20 221K R21 221K C13 0.01uF C14 0.01uF C15 0.01uF +3.3VD R22 200K SW2 RANGE SW3 T ARE SW4 CAL SW5 CONFIG +3.3VD 10K 10K 10K R10 10K R12 100 R13 100 C25 2.2uF +3.3VD 910 1112 1314 HEADER-7X2 +3.3VD SW6 RESET +3.3VD 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 181716151413121110987654321 LCD1 LCD_DISPLAY TDO/TDI TDI/CLK TMS TCK RST BSLRX BSL TX MCURX MCUTX DOUT SCLK SPEED PDWN COM(3) COM(2) COM(1) COM(0) S(39) COM(3) COM(2) COM(1)COM(0) S(38) S(37) S(36) S(35) S(34) S(33) S(32) S(31) S(30) S(29) S(28) S(27) S(26) S(25) S(24) S(23) S(22) S(21) S(20) S(19) S(18) S(17) S(16) S(15) S(14) S(36)S(35) S(34)S(33) S(32)S(31) S(30)S(29) S(28)S(27) S(26)S(25) S(24)S(23) S(22)S(21) S(20)S(19) S(18)S(17) S(16)S(15) S(14) S(5) S(6) S(7) S(8) S(9) S(10) S(11) S(12) S(13) 0.01uF C23 2.2uF C24 2.2uF SW8 NKK_SS12SDP2 R16 10K +3.3VD R18 47K DOUT TP18 MCURX TP8 MCUTX SIMO0 TP7 DNP RST TCK EPS_C-002RX 32.7680K-A:PBFREE TP5 P1.4/SMCLK VCC 1D- 2D+ 3GND 4 USB SLAVE CONN CTS 13 DCD 15DSR 14DTR 21 RTS 20 SIN/IR_SIN 17SOUT/IR_SOUT 19 SDA SCL X226 X1/CLKI27 CLKOUT22 PUR5 DP6 DM7 RESET GND8 GND18 GND28 SUSPEND VREGEN RI/CP 16 WAKEUP TEST1 24TEST0 23 P3.0 P3.1 P3.3 P3.4 VCC VCC VDD TUSB3410VF 1.5K C16 22pF C17 22pF 12MHzC1 22pF 22pF C22 1uF USB3.3V USB3.3VUSB5V 10K C18 10uF GREEN R11 220 FERRITE BEAD TP1 USB_CLK 10K 10K C37 MUR_NFM21PC105F1C3D SW1 USB RESET TP2 3.3V_USB RX TX R TS DTRC3 4.7uF R17 FB/SENSE 1 RESET 2EN3 GND4 IN5 IN6 OUT 7 OUT 8 TPS77133DGK 2 4 U10 SN74LVC1G04DBV2 4 SN74LVC1G04DBV USB3.3V USB3.3V USB3.3V USB3.3V USB3.3V +3.3VD +3.3VD MCURX MCUTX TP16 RX TP17 TX VCC11 IN2 VCC13 GND14 GND2 5 OUT 6 GND2 7 VCC2 8 ISO721D VCC1 1 IN 2VCC1 3 GND1 4GND25 OUT6 GND27 VCC28 ISO721D C10 1uF PROGRAMMING MODE RST TCK +5V USB5V+5VA C12 0.1uF C21 0.1uF C33 0.1uF C34 0.1uF C35 0.1uF C36 0.1uF SW9 ESW_EG4208 Schematics www.ti.com Figure14.ADS1x31REF Schematic—MCU Figure15.ADS1x31REF Schematic—USB

28 Schematicand Layout SBAU175A –July2010–RevisedAugust2011

www.ti.com RevisionHistory RevisionHistory NOTE: Page numbers forpreviousrevisionsmay differfrompage numbers inthecurrentversion. 29SBAU175A –July2010–RevisedAugust2011 RevisionHistory SubmitDocumentationFeedback Copyright© 2010–2011,Texas InstrumentsIncorporated

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Product Information

1656A specifications and overview.

Summary

ADS1131REF and ADS1231REF

Description

ADS1131REF and ADS1231REF

Source title 1656A Datasheet(PDF) - Texas Instruments

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