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CircuitNoteCN-0301CircuitsfromtheLabreferencedesignsareengineeredandtestedforquickandeasysystemintegrationtohelpsolvetoday'sanalog,mixed-signal,andRFdesignchallenges.
Formoreinformationand/orsupport,visitwww.
analog.
com/CN0301.
DevicesConnected/ReferencedAD698UniversalLVDTSignalConditionerAD8615Precision,20MHz,CMOS,SingleRRIOOperationalAmplifierAD79922-Channel,12-BitADCwithI2C-CompatibleInterfacein10-LeadMSOPUniversalLVDTSignalConditioningCircuitRev.
ACircuitsfromtheLabreferencedesignsfromAnalogDeviceshavebeendesignedandbuiltbyAnalogDevicesengineers.
Standardengineeringpracticeshavebeenemployedinthedesignandconstructionofeachcircuit,andtheirfunctionandperformancehavebeentestedandverifiedinalabenvironmentatroomtemperature.
However,youaresolelyresponsiblefortestingthecircuitanddeterminingitssuitabilityandapplicabilityforyouruseandapplication.
Accordingly,innoeventshallAnalogDevicesbeliablefordirect,indirect,special,incidental,consequentialorpunitivedamagesduetoanycausewhatsoeverconnectedtotheuseofanyCircuitsfromtheLabcircuits.
(Continuedonlastpage)OneTechnologyWay,P.
O.
Box9106,Norwood,MA02062-9106,U.
S.
A.
Tel:781.
329.
4700www.
analog.
comFax:781.
461.
31132013–2014AnalogDevices,Inc.
Allrightsreserved.
EVALUATIONANDDESIGNSUPPORTCircuitEvaluationBoardsCN-0301CircuitEvaluationBoard(EVAL-CN0301-SDPZ)SystemDemonstrationPlatform(EVAL-SDP-CB1Z)DesignandIntegrationFilesSchematics,LayoutFiles,BillofMaterialsCIRCUITFUNCTIONANDBENEFITSThecircuitshowninFigure1isacompleteadjustment-freelinearvariabledifferentialtransformer(LVDT)signalconditioningcircuit.
Thiscircuitcanaccuratelymeasurelineardisplacement(position).
TheLVDTisahighlyreliablesensorbecausethemagneticcorecanmovewithoutfrictionanddoesnottouchtheinsideofthetube.
Therefore,LVDTsaresuitableforflightcontrolfeedbacksystems,positionfeedbackinservomechanisms,automatedmeasurementinmachinetools,andmanyotherindustrialandscientificelectromechanicalapplicationswherelongtermreliabilityisimportant.
ThiscircuitusestheAD698LVDTsignalconditionerthatcontainsasinewaveoscillatorandapoweramplifiertogeneratetheexcitationsignalsthatdrivetheprimarysideoftheLVDT.
TheAD698alsoconvertsthesecondaryoutputintoadcvoltage.
TheAD8615rail-to-railamplifierbufferstheoutputoftheAD698anddrivesalowpower12-bitsuccessiveapproximationanalog-to-digitalconverter(ADC).
Thesystemhasadynamicrangeof82dBandasystembandwidthof250Hz,makingitidealforprecisionindustrialpositionandgaugingapplications.
Thesignalconditioningcircuitryofthesystemconsumesonly15mAofcurrentfromthe±15Vsupplyand3mAfromthe+5Vsupply.
ThiscircuitnotediscussesbasicLVDTtheoryofoperationandthedesignstepsusedtooptimizethecircuitshowninFigure1forachosenbandwidth,includingnoiseanalysisandcomponentselectionconsiderations.
Figure1.
UniversalLVDTSignalConditioningCircuit(SimplifiedSchematic:AllConnectionsandDecouplingNotShown)EXCITATION(CARRIER)AD8615+5V3kΩ0.
01F33Ω2.
7nFAD698VOUT+15V–15VVOLTAGEREFERENCEOSCAMPBABALPFAMPAD7992VIN1+5VE-100ECONOMYSERIESLVDTSDASCLALERT11607-001CN-0301CircuitNoteRev.
A|Page2of7CIRCUITDESCRIPTIONTheoryofOperationAnLVDTisanabsolutedisplacementtransducerthatconvertsalineardisplacementorpositionfromamechanicalreference(orzero)intoaproportionalelectricalsignalcontainingphase(fordirection)andamplitudeinformation(fordistance).
TheLVDToperationdoesnotrequireelectricalcontactbetweenthemovingpart(probeorcorerodassembly)andthetransformer.
Instead,itreliesonelectromagneticcoupling.
Forthisreason,andbecausetheyoperatewithoutanybuilt-inelectroniccircuitry,LVDTsarewidelyusedinapplicationswherelonglifeandhighreliabilityundersevereenvironmentsarearequired,suchmilitaryandaerospaceapplications.
Forthiscircuit,theE-100EconomySeriesLVDTsensorfromMeasurementSpecialties,Inc.
wasusedwiththeAD698.
Withalinearityof±0.
5%offullrange,theESeriesissuitableformostapplicationswithmoderateoperationtemperatureenvironments.
TheAD698isacomplete,LVDTsignalconditioningsubsystem.
ItconvertsthetransducermechanicalpositionofLVDTstoaunipolardcvoltagewithahighdegreeofaccuracyandrepeatability.
Allcircuitfunctionsareincludedonthechip.
Withtheadditionofafewexternalpassivescomponentstosetfrequencyandgain,theAD698convertstherawLVDTsecondaryoutputtoascaleddcsignal.
TheAD698containsalowdistortionsinewaveoscillatortodrivetheLVDTprimary.
Thefrequencyofthesinewaveisdeterminedbyasinglecapacitorandcanrangefrom20Hzto20kHzwithamplitudesfrom2Vrmsto24Vrms.
TheLVDTsecondaryoutputconsistsoftwosinewavesthatdrivetheAD698directly.
TheAD698decodesLVDTsbysynchronouslydemodulatingtheamplitudemodulatedinput(secondaries),A,andafixedinputreference(primaryorsumofsecondariesorfixedinput),B.
Acommonproblemwithearliersolutionswasthatanydriftintheamplitudeofthedriveoscillatorcorrespondeddirectlytoagainerrorintheoutput.
TheAD698eliminatestheseerrorsbycalculatingtheratiooftheLVDToutputtoitsinputexcitationinordertocanceloutanydrifteffects.
ThisdevicediffersfromtheAD598LVDTsignalconditionerinthatitimplementsadifferentcircuittransferfunctionanddoesnotrequirethesumoftheLVDTsecondaries(A+B)tobeconstantwithstrokelength.
TheblockdiagramoftheAD698isdepictedFigure2.
Theinputsconsistoftwoindependentsynchronousdemodulationchannels.
TheBchannelmonitorsthedriveexcitationtotheLVDT.
ThefullwaverectifiedoutputisfilteredbyC2beforebeingsenttothecomputationalcircuit.
ChannelAisidenticalexceptthatthecomparator'spinsareexternallyavailable.
SincetheAchannelmayreach0VoutputattheLVDTnull,theAchanneldemodulatorisusuallytriggeredbytheprimaryvoltage(BChannel).
Inaddition,aphasecompensationnetworkmayberequiredtoaddphaseleadorlagtotheAChanneltocompensatefortheLVDTprimarytosecondaryphaseshift.
Forhalf-bridgecircuitsthephaseshiftinnoncritical,andtheAchannelvoltageislargeenoughtotriggerthedemodulator.
Figure2.
AD698BlockDiagramOncebothchannelsaredemodulatedandfilteredadivisioncircuit,implementedwithadutycyclemultiplier,isusedtocalculatetheratioA/B.
Theoutputofthedividerisadutycycle.
WhenA/Bisequalto1,thedutycyclewillbeequalto100%.
(Thissignalcanbeusedasisifapulsewidthmodulatedoutputisrequired.
)Thedutycycledrivesacircuitthatmodulatesandfiltersareferencecurrentproportionaltothedutycycle.
Theoutputamplifierscalesthe500Areferencecurrentconvertingtoavoltage.
Theoutputtransferfunctionisthus:2RBAIVREFOUT**=whereIREF=500μA.
LPFLPF±1V/IV/ICOMPCOMP±1C2C5ABR2FBC4OUTFILTEROFF2IREF500AOFF1BFILT1–BIN+BIN–ACOMP+ACOMP–AIN+AINACHANNELDUTYCYCLEDIVIDERA/B=1=100%DUTYDEMODULATORAD698BCHANNELBFILT2C3AFILT1AFILT2+VS–VSVOUTV11607-002CircuitNoteCN-0301Rev.
A|Page3of7ComponentSelectionThedesignprocedureforthedualsupplyoperation(±15V)foundintheAD698datasheetwasfollowedtosettheexcitationfrequencyto2.
5kHz,systembandwidthto250Hz,andanoutputvoltagefrom0Vto5V.
ItisnormalfortheAD698internaloscillatortoproduceasmallamountofripplethatfeedsthroughtotheoutput.
Apassivelow-passfilterisusedtoreducethisrippletotherequiredlevel.
Whenselectingcapacitorvaluestosetthebandwidthofthesystem,atrade-offisinvolved.
Choosingsmallercapacitorsgivehighersystembandwidthbutincreasetheamountofoutputvoltageripple.
Theripplecanbereducedbyincreasingtheshuntcapacitanceacrossthefeedbackresistorusedtosettheoutputvoltagelevel;however,thisalsoincreasesphaselag.
TheAD8615operationalamplifierbufferstheoutputoftheAD698,whichensuresthattheAD7992ADCisdrivenbyalowimpedancesource(highsourceimpedancessignificantlyaffecttheacperformanceoftheADC).
Thelow-passfilterbetweentheoutputoftheAD698andtheinputoftheAD8615servestwopurposes:ItlimitstheinputcurrenttotheAD8615.
Itfilterstheoutputvoltageripple.
TheAD8615hasinternalprotectivecircuitrythatallowsvoltagesexceedingthesupplytobeappliedattheinput.
ThisisimportantbecausetheoutputvoltageoftheAD698canswing±11Vwith±15Vsupplies.
Aslongastheinputcurrentislimitedtolessthan5mA,highervoltagescanbeappliedtotheinput.
ThisisprimarilyduetotheextremelylowinputbiascurrentoftheAD8615(1pA)whichallowstheuseoflargerresistors.
Theuseoftheseresistorsaddsthermalnoise,whichcontributestotheoveralloutputvoltagenoiseoftheamplifier.
TheAD8615isanidealamplifiertobufferanddrivetheinputoftheAD799212-bitSARADCbecauseofitsinputovervoltageprotection,anditsabilitytoswingrail-to-railatboththeinputandoutput.
NoiseAnalysisWithallsignalconditioncomponentsselected,theamountofresolutionneededtoconvertthesignalmustbedetermined.
Asinmostnoiseanalyses,onlythekeycontributorsneedtobeidentified.
Noisesourcescombineinanrssmanner;therefore,anysinglenoisesourcethatisatleastthree-to-fourtimeslargerthananyoftheothersdominates.
InthecaseoftheLVDTsignalconditioningcircuit,thedominantsourceoftheoutputnoiseistheoutputrippleoftheAD698.
Theothersourcesofnoise(resistornoise,inputvoltagenoise,andoutputvoltagenoiseoftheAD8615)aresignificantlysmallerincomparison.
TheoutputvoltagerippleoftheAD698is0.
4mVrmswitha0.
39Fcapacitorvalueandwitha10nFshuntcapacitoracrossthefeedbackresistorshowninFigure3.
NotethatthesecomponentsandrelatedpinconnectionsarenotshowninthesimplifiedschematicinFigure1;however,detailscanbefoundintheAD698datasheet.
Figure3.
OutputVoltageRipplevs.
FilterCapacitanceThemaximumnumberofrmscountsthatcanberesolvedcannowbecalculatedbydividingthefull-scaleoutputbythetotalsystemrmsnoise.
TotalRMSCounts=5V/0.
4mV=12,500Theeffectiveresolutionisfoundbytakingthebase2logarithmofthetotalrmscounts.
EffectiveResolution=log2(12,500)=13.
6BitsNoise-freecoderesolutioncanbeobtainedbysubtracting2.
7bitsfromtheeffectiveresolution.
Noise-FreeCodeResolution=EffectiveResolution2.
7Bits=13.
6Bits2.
7Bits=10.
9BitsThetotaloutputdynamicrangeofthesystemcanbecalculatedbydividingthefull-scaleoutputsignal(5V)bythetotaloutputrmsnoise(0.
4mVrms)andconvertingittodecibels,yieldingapproximately82dB.
DynamicRange=20log(5V/0.
4mV)=82dBTheAD7992isagoodcandidateforthisapplicationbecauseithas12-bitresolutionandasamplingrateof188kSPSperchannelwhenusedwitha3.
4MHzserialclock.
10001001010.
10.
0010.
010.
111011607-003RIPPLE(mVrms)C2,C3,C4;C2=C3=C4(F)10kHz,CSHUNT=1nF10kHz,CSHUNT=10nFCN-0301CircuitNoteRev.
A|Page4of7CompensatingforPhaseLag/LeadTheAD698usesdemodulationtogenerateanoutputsignalbymultiplyingthereturnsignalwiththereferenceoscillatorfedtotheprimary.
Smallamountsofphaseshiftcanproducesignificantlinearityerrorwhichisseenasundershootintheoutput.
Thephaseleadnetworkcompensatesforthe3°ofprimarytosecondaryphaseshiftoftheE-100seriesLVDT.
Figure4showstwodifferentphasecompensationnetworks.
Figure4.
PhaseLag/LeadNetworkWhenchoosingcomponentvaluesfortheappropriatenetwork,itisimportanttonotethatRSandRTeffectivelyconstitutearesistordividerthatreducestheamplitudeoftheexcitationsignalsbeforeitreachesthe±ACOMPinputsoftheAD698.
ThissuggeststhatRTneedstobemuchlargerthanRS.
Thelag/leadcircuitryalsoaddsloadtotheexcitationoutputtherefore,largerresistivevaluesarerecom-mended.
Theendgoalistoachievethedesiredphaselag/leadontheACOMPinputsoftheAD698withasmallamplitudedrop.
Theamountofphaselag/leadcanbecalculatedbyusingthefollowingformulas:()CRHzLagPhase**=1tan**=CRHzLeadPhase1tan1whereTSSRRRR++=11Hz=ExcitationFrequencyTestResultsUsingaMeasurementSpecialties,Inc.
E-100EconomySeriesLVDTconnectedtoJ3andusingadigitaloscilloscopetomonitortheoutputoftheAD698foundonJ6ontheEVAL-CN0301-SDPZevaluationboard,theactualoutputripplefoundwas6.
6mVp-p,asisshowninFigure5.
Figure5.
OutputVoltageRippleBeforeLow-PassFilterThelow-passfilter(3k,0.
01F)betweentheAD698outputandtheAD8615inputhasa3dBbandwidthof5.
3kHzandreducestherippleto2mVp-p.
Withthelow-passfilterinstalledbetweentheoutputstageoftheAD698andtheinputstageoftheAD8615,datawascollectedfromtheEVAL-CN0301-SDPZevaluationboard,asshowninFigure6.
Figure6.
ScreenshotoftheCN-0301EvaluationSoftwareTheripplefromtheAD698wasattenuatedto2mVp-p,andthesystemwasabletoachieve11bitsofnoise-freecoderesolution.
Acompletedesignsupportpackageforthiscircuitnotecanbefoundathttp://www.
analog.
com/CN0301-DesignSupport.
ApplicationsinFlightControlSurfacePositionFeedbackUnmannedautonomousvehicles(UAVs),ordrones,areplayinganever-increasingpartinthenationalsecurityoftheUnitedStates.
Thesehightechnology,complexaerialplatformsarecontrolledbyacrewmilesawayandaremultimissioncapable.
Theyincluderolessuchasaerialreconnaissance,combatweaponsplatforms,battlefieldtheatercommandandcontroloversight,orunmannedin-flightrefuelingstation.
PHASELAGPHASELEADABCCRSRSRTDABCRTRSCCD11607-004CH12.
0mVM2.
000s111607-00511607-006CircuitNoteCN-0301Rev.
A|Page5of7ThecomplexsystemsemployedonUAVsuseamyriadofelectronicsensorsforprecisecontrolandfeedback.
Tocontrolthealtitude(pitch,roll,andyaw)oftheUAV,actuatorsareusedtoexertforcesontheflightcontrolsurfaces.
Theprecisemeasurementofthepositionoftheseactuatorsiscrucialinmaintainingtheproperflightofpath.
Thesensorsusedtomeasureactuatorpositionneedtomeetthreeessentialcriteria:highaccuracy,highreliability,andlightweight.
AllthreeoftheseattributesarefoundintheLVDTsdesignedbyMeasurementSpecialties,Inc.
SynchronousOperationofMultipleLVDTsInmanyapplications,suchasmultiplegagingmeasurement,alargenumberofLVDTsareusedincloseproximity.
IftheseLVDTsoperateatsimilarcarrierfrequencies,straymagneticcouplingcancausebeatnotestobegenerated.
Theresultingbeatnotesmayinterferewiththeaccuracyofmeasurementsmadeundertheseconditions.
Toavoidthissituation,allLVDTsoperatesynchronously.
TheEVAL-CN0301-SDPZevaluationboardcanbeconfiguredtohaveonemasteroscillatorbetweentwoLVDTsbypopulatingJumperJP1,JP2,andJP4withashortingjumperandleavingJP3unpopulated.
EachLVDTprimaryisdrivenfromitsownpoweramplifier,and,thus,thethermalloadissharedbetweentheAD698devices.
COMMONVARIATIONSThecomponentsselectedwereoptimizedforamaximum5VunipolaroutputfromtheAD698;however,othercombinationscanbesubstituted.
Othersuitablesingle-supplyamplifiersaretheAD8565andAD8601.
TheseamplifiersaresuitablereplacementsfortheAD8615becausetheyhaveinputovervoltageprotectionandtheabilitytoswingrail-to-railatboththeinputandoutput.
Ifdual-supplyoperationisrequired,theADA4638-1orADA4627-1issuggested.
IftheAD698outputs±10Vbipolarsignals,theAD7321issuggested.
TheAD7321isa2-channel,bipolarinput,12-bitADCthatcanaccepttruebipolaranaloginputsignalsaslargeas±10V.
CIRCUITEVALUATIONANDTESTThiscircuitusestheEVAL-CN0301-SDPZcircuitboardandtheEVAL-SDP-CB1ZSDP-Bsystemdemonstrationplatformcontrollerboard.
Thetwoboardshave120-pinmatingconnectors,allowingforthequicksetupandevaluationoftheperformanceofthecircuit.
TheEVAL-CN0301-SDPZcontainsthecircuittobeevaluated,andtheEVAL-SDP-CB1Z(SDP-B)isusedwiththeCN-0301EvaluationSoftwaretocapturethedatafromtheEVAL-CN0301-SDPZ.
EquipmentNeededThefollowingequipmentisneeded:APCwithaUSBportandWindowsXP(32bit),WindowsVista,orWindows7TheEVAL-CN0301-SDPZcircuitboardTheEVAL-SDP-CB1ZSDP-BcontrollerboardTheCN-0301EvaluationSoftwareTheEVAL-CFTL-6V-PWRZdcpowersupplyorequivalent6V/1AbenchsupplyMeasurementSpecialties,Inc.
,E-100EconomySeriesLVDT(EVAL-CFTL-LVDT)GettingStartedLoadtheevaluationsoftwarebyplacingtheCN-0301EvaluationSoftwareintotheCDdriveofthePC.
UsingMyComputer,locatethedrivethatcontainstheevaluationsoftware.
FunctionalBlockDiagramSeeFigure1forthecircuitblockdiagramandtheEVAL-CN0301-SDPZ-PADSSchematic.
pdffileforthecompletecircuitschematic.
ThePDFfilecanbefoundintheCN-0301DesignSupportPackage.
Figure7.
TestSetupBlockDiagramSetupConnectthe120-pinconnectorontheEVAL-CN0301-SDPZtotheCONAconnectorontheEVAL-SDP-CB1Z(SDP-B).
Usenylonhardwaretofirmlysecurethetwoboards,usingtheholesprovidedattheendsofthe120-pinconnectors.
Withpowertothesupplyoff,connecta6Vpowersupplytothe+6VandGNDpinsontheboard.
Ifavailable,a6Vwallwartcanbeconnectedtothebarrelconnectorontheboardandusedinplaceofthe6Vpowersupply.
ConnecttheUSBcablesuppliedwiththeEVAL-SDP-CB1ZtotheUSBportonthePC.
DonotconnecttheUSBcabletotheMini-USBconnectorontheEVAL-SDP-CB1Zatthistime.
TestApplypowertothe6Vsupply(orwallwart)connectedtotheEVAL-CN0301-SDPZ.
LaunchtheevaluationsoftwareandconnecttheUSBcablefromthePCtotheMini-USBconnectorontheEVAL-SDP-CB1Z.
WhenUSBcommunicationsareestablished,theEVAL-SDP-CB1Zcansend,receive,andcaptureparalleldatafromtheEVAL-CN0301-SDPZ.
Figure8showsaphotooftheEVAL-CN0301-SDPZconnectedtotheEVAL-SDP-CB1Z.
InformationregardingtheEVAL-SDP-CB1ZcanbefoundintheUG-277UserGuide.
120PINSJ4J1J8EVAL-CN0301-SDPZBOARDMEASUREMENTSPECIALTIES,INC.
E-100ECONOMYSERIESLVDTEVAL-CFTL-LVDTEVAL-SDP-CB1ZSDP-BBOARDUSBCONAEVAL-CFTL-6V-PWRZ6VWALLWARTPC11607-007CN-0301CircuitNoteRev.
A|Page6of7Informationanddetailsregardingtestsetupandcalibration,andhowtousetheevaluationsoftwarefordatacapturecanbefoundintheCN-0301SoftwareUserGuide.
ConnectivityforPrototypeDevelopmentTheEVAL-CN0301-SDPZisdesignedtousetheEVAL-SDP-CB1Z;however,anymicroprocessorcanbeusedtointerfacetotheI2C2-wireserialinterfaceoftheAD7992.
InorderforanothercontrollertobeusedwiththeEVAL-CN0301-SDPZ,softwaremustbedevelopedbyathirdparty.
ThereareexistinginterposerboardsthatcanbeusedtointerfacetotheAlteraandXilinxfieldprogrammablegatearrays(FPGAs).
TheBeMicroSDKboardfromAlteracanbeusedwiththeBeMicroSDK/SDPinterposerusingniosdrivers.
AnyXilinxevaluationboardthatfeaturestheFMCconnectorcanbeusedwiththeFMC-SDPinterposerboard.
TheEVAL-CN0301-SDPZisalsocompatiblewiththeDigilent,Imodinterfacespecification.
AphotoofthesystemisshowninFigure8.
Figure8.
TheEVAL-CN0301-SDPZBoardConnectedtoEVAL-SDP-CB1Z(SDP-B)BoardandMeasurementSpecialties,Inc.
,E-100EconomySeriesLVDTUSBEVAL-CN0301-SDPZEVAL-SDP-CB1ZEVAL-CFTL-6V-PWRZMEASUREMENTSPECIALTIES,INC.
E-100ECONOMYSERIESLVDTEVAL-CFTL-LVDT11607-008CircuitNoteCN-0301Rev.
A|Page7of7LEARNMORECN-0301DesignSupportPackage:http://www.
analog.
com/CN0301-DesignSupportSDP-BUserGuideArdizzoni,John.
APracticalGuidetoHigh-SpeedPrinted-Circuit-BoardLayout.
AnalogDialogue39-09,September2005.
MT-004Tutorial,TheGood,theBad,andtheUglyAspectsofADCInputNoise—IsNoNoiseGoodNoise,AnalogDevices.
MT-031Tutorial,GroundingDataConvertersandSolvingtheMysteryof"AGND"and"DGND",AnalogDevices.
MT-035,OpAmpInputs,Outputs,Single-Supply,andRail-to-RailIssues,AnalogDevices.
MT-036Tutorial,OpAmpOutputPhase-ReversalandInputOver-VoltageProtection,AnalogDevices.
MT-068Tutorial,DifferenceandCurrentSenseAmplifiers,AnalogDevices.
MT-101Tutorial,DecouplingTechniques,AnalogDevices.
AN-1106ApplicationNote,AnImprovedTopologyforCreatingSplitRailsfromaSingleInputVoltage,AnalogDevices.
E-100EconomySeriesLVDT,MeasurementSpecialties,Inc.
TheLVDT:constructionandprincipleofoperation,TechnicalPaper,MeasurementSpecialties,Inc.
,1000LucasWay,Hampton,VA23666.
SubminiatureLVDTsProvideAccurateFlightControlSurfacePositionFeedbackonUAVs,ApplicationNote,MeasurementSpecialties,Inc.
,1000LucasWay,Hampton,VA23666.
DataSheetsandEvaluationBoardsCN-0301CircuitEvaluationBoard(EVAL-CN0301-SDPZ)SystemDemonstrationPlatform(EVAL-SDP-CB1Z)AD698DataSheetAD7992DataSheetAD8615DataSheetADP1613DataSheetADP7104DataSheetREVISIONHISTORY3/14—Rev.
0toRev.
AChangestoSynchronousOperationofMultipleLVDTsSection.
.
.
.
.
55/13—Revision0:InitialVersion(Continuedfromfirstpage)CircuitsfromtheLabreferencedesignsareintendedonlyforusewithAnalogDevicesproductsandaretheintellectualpropertyofAnalogDevicesoritslicensors.
WhileyoumayusetheCircuitsfromtheLabreferencedesignsinthedesignofyourproduct,nootherlicenseisgrantedbyimplicationorotherwiseunderanypatentsorotherintellectualpropertybyapplicationoruseoftheCircuitsfromtheLabreferencedesigns.
InformationfurnishedbyAnalogDevicesisbelievedtobeaccurateandreliable.
However,CircuitsfromtheLabreferencedesignsaresupplied"asis"andwithoutwarrantiesofanykind,express,implied,orstatutoryincluding,butnotlimitedto,anyimpliedwarrantyofmerchantability,noninfringementorfitnessforaparticularpurposeandnoresponsibilityisassumedbyAnalogDevicesfortheiruse,norforanyinfringementsofpatentsorotherrightsofthirdpartiesthatmayresultfromtheiruse.
AnalogDevicesreservestherighttochangeanyCircuitsfromtheLabreferencedesignsatanytimewithoutnoticebutisundernoobligationtodoso.
2013–2014AnalogDevices,Inc.
Allrightsreserved.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
CN11607-0-3/14(A)
Formoreinformationand/orsupport,visitwww.
analog.
com/CN0301.
DevicesConnected/ReferencedAD698UniversalLVDTSignalConditionerAD8615Precision,20MHz,CMOS,SingleRRIOOperationalAmplifierAD79922-Channel,12-BitADCwithI2C-CompatibleInterfacein10-LeadMSOPUniversalLVDTSignalConditioningCircuitRev.
ACircuitsfromtheLabreferencedesignsfromAnalogDeviceshavebeendesignedandbuiltbyAnalogDevicesengineers.
Standardengineeringpracticeshavebeenemployedinthedesignandconstructionofeachcircuit,andtheirfunctionandperformancehavebeentestedandverifiedinalabenvironmentatroomtemperature.
However,youaresolelyresponsiblefortestingthecircuitanddeterminingitssuitabilityandapplicabilityforyouruseandapplication.
Accordingly,innoeventshallAnalogDevicesbeliablefordirect,indirect,special,incidental,consequentialorpunitivedamagesduetoanycausewhatsoeverconnectedtotheuseofanyCircuitsfromtheLabcircuits.
(Continuedonlastpage)OneTechnologyWay,P.
O.
Box9106,Norwood,MA02062-9106,U.
S.
A.
Tel:781.
329.
4700www.
analog.
comFax:781.
461.
31132013–2014AnalogDevices,Inc.
Allrightsreserved.
EVALUATIONANDDESIGNSUPPORTCircuitEvaluationBoardsCN-0301CircuitEvaluationBoard(EVAL-CN0301-SDPZ)SystemDemonstrationPlatform(EVAL-SDP-CB1Z)DesignandIntegrationFilesSchematics,LayoutFiles,BillofMaterialsCIRCUITFUNCTIONANDBENEFITSThecircuitshowninFigure1isacompleteadjustment-freelinearvariabledifferentialtransformer(LVDT)signalconditioningcircuit.
Thiscircuitcanaccuratelymeasurelineardisplacement(position).
TheLVDTisahighlyreliablesensorbecausethemagneticcorecanmovewithoutfrictionanddoesnottouchtheinsideofthetube.
Therefore,LVDTsaresuitableforflightcontrolfeedbacksystems,positionfeedbackinservomechanisms,automatedmeasurementinmachinetools,andmanyotherindustrialandscientificelectromechanicalapplicationswherelongtermreliabilityisimportant.
ThiscircuitusestheAD698LVDTsignalconditionerthatcontainsasinewaveoscillatorandapoweramplifiertogeneratetheexcitationsignalsthatdrivetheprimarysideoftheLVDT.
TheAD698alsoconvertsthesecondaryoutputintoadcvoltage.
TheAD8615rail-to-railamplifierbufferstheoutputoftheAD698anddrivesalowpower12-bitsuccessiveapproximationanalog-to-digitalconverter(ADC).
Thesystemhasadynamicrangeof82dBandasystembandwidthof250Hz,makingitidealforprecisionindustrialpositionandgaugingapplications.
Thesignalconditioningcircuitryofthesystemconsumesonly15mAofcurrentfromthe±15Vsupplyand3mAfromthe+5Vsupply.
ThiscircuitnotediscussesbasicLVDTtheoryofoperationandthedesignstepsusedtooptimizethecircuitshowninFigure1forachosenbandwidth,includingnoiseanalysisandcomponentselectionconsiderations.
Figure1.
UniversalLVDTSignalConditioningCircuit(SimplifiedSchematic:AllConnectionsandDecouplingNotShown)EXCITATION(CARRIER)AD8615+5V3kΩ0.
01F33Ω2.
7nFAD698VOUT+15V–15VVOLTAGEREFERENCEOSCAMPBABALPFAMPAD7992VIN1+5VE-100ECONOMYSERIESLVDTSDASCLALERT11607-001CN-0301CircuitNoteRev.
A|Page2of7CIRCUITDESCRIPTIONTheoryofOperationAnLVDTisanabsolutedisplacementtransducerthatconvertsalineardisplacementorpositionfromamechanicalreference(orzero)intoaproportionalelectricalsignalcontainingphase(fordirection)andamplitudeinformation(fordistance).
TheLVDToperationdoesnotrequireelectricalcontactbetweenthemovingpart(probeorcorerodassembly)andthetransformer.
Instead,itreliesonelectromagneticcoupling.
Forthisreason,andbecausetheyoperatewithoutanybuilt-inelectroniccircuitry,LVDTsarewidelyusedinapplicationswherelonglifeandhighreliabilityundersevereenvironmentsarearequired,suchmilitaryandaerospaceapplications.
Forthiscircuit,theE-100EconomySeriesLVDTsensorfromMeasurementSpecialties,Inc.
wasusedwiththeAD698.
Withalinearityof±0.
5%offullrange,theESeriesissuitableformostapplicationswithmoderateoperationtemperatureenvironments.
TheAD698isacomplete,LVDTsignalconditioningsubsystem.
ItconvertsthetransducermechanicalpositionofLVDTstoaunipolardcvoltagewithahighdegreeofaccuracyandrepeatability.
Allcircuitfunctionsareincludedonthechip.
Withtheadditionofafewexternalpassivescomponentstosetfrequencyandgain,theAD698convertstherawLVDTsecondaryoutputtoascaleddcsignal.
TheAD698containsalowdistortionsinewaveoscillatortodrivetheLVDTprimary.
Thefrequencyofthesinewaveisdeterminedbyasinglecapacitorandcanrangefrom20Hzto20kHzwithamplitudesfrom2Vrmsto24Vrms.
TheLVDTsecondaryoutputconsistsoftwosinewavesthatdrivetheAD698directly.
TheAD698decodesLVDTsbysynchronouslydemodulatingtheamplitudemodulatedinput(secondaries),A,andafixedinputreference(primaryorsumofsecondariesorfixedinput),B.
Acommonproblemwithearliersolutionswasthatanydriftintheamplitudeofthedriveoscillatorcorrespondeddirectlytoagainerrorintheoutput.
TheAD698eliminatestheseerrorsbycalculatingtheratiooftheLVDToutputtoitsinputexcitationinordertocanceloutanydrifteffects.
ThisdevicediffersfromtheAD598LVDTsignalconditionerinthatitimplementsadifferentcircuittransferfunctionanddoesnotrequirethesumoftheLVDTsecondaries(A+B)tobeconstantwithstrokelength.
TheblockdiagramoftheAD698isdepictedFigure2.
Theinputsconsistoftwoindependentsynchronousdemodulationchannels.
TheBchannelmonitorsthedriveexcitationtotheLVDT.
ThefullwaverectifiedoutputisfilteredbyC2beforebeingsenttothecomputationalcircuit.
ChannelAisidenticalexceptthatthecomparator'spinsareexternallyavailable.
SincetheAchannelmayreach0VoutputattheLVDTnull,theAchanneldemodulatorisusuallytriggeredbytheprimaryvoltage(BChannel).
Inaddition,aphasecompensationnetworkmayberequiredtoaddphaseleadorlagtotheAChanneltocompensatefortheLVDTprimarytosecondaryphaseshift.
Forhalf-bridgecircuitsthephaseshiftinnoncritical,andtheAchannelvoltageislargeenoughtotriggerthedemodulator.
Figure2.
AD698BlockDiagramOncebothchannelsaredemodulatedandfilteredadivisioncircuit,implementedwithadutycyclemultiplier,isusedtocalculatetheratioA/B.
Theoutputofthedividerisadutycycle.
WhenA/Bisequalto1,thedutycyclewillbeequalto100%.
(Thissignalcanbeusedasisifapulsewidthmodulatedoutputisrequired.
)Thedutycycledrivesacircuitthatmodulatesandfiltersareferencecurrentproportionaltothedutycycle.
Theoutputamplifierscalesthe500Areferencecurrentconvertingtoavoltage.
Theoutputtransferfunctionisthus:2RBAIVREFOUT**=whereIREF=500μA.
LPFLPF±1V/IV/ICOMPCOMP±1C2C5ABR2FBC4OUTFILTEROFF2IREF500AOFF1BFILT1–BIN+BIN–ACOMP+ACOMP–AIN+AINACHANNELDUTYCYCLEDIVIDERA/B=1=100%DUTYDEMODULATORAD698BCHANNELBFILT2C3AFILT1AFILT2+VS–VSVOUTV11607-002CircuitNoteCN-0301Rev.
A|Page3of7ComponentSelectionThedesignprocedureforthedualsupplyoperation(±15V)foundintheAD698datasheetwasfollowedtosettheexcitationfrequencyto2.
5kHz,systembandwidthto250Hz,andanoutputvoltagefrom0Vto5V.
ItisnormalfortheAD698internaloscillatortoproduceasmallamountofripplethatfeedsthroughtotheoutput.
Apassivelow-passfilterisusedtoreducethisrippletotherequiredlevel.
Whenselectingcapacitorvaluestosetthebandwidthofthesystem,atrade-offisinvolved.
Choosingsmallercapacitorsgivehighersystembandwidthbutincreasetheamountofoutputvoltageripple.
Theripplecanbereducedbyincreasingtheshuntcapacitanceacrossthefeedbackresistorusedtosettheoutputvoltagelevel;however,thisalsoincreasesphaselag.
TheAD8615operationalamplifierbufferstheoutputoftheAD698,whichensuresthattheAD7992ADCisdrivenbyalowimpedancesource(highsourceimpedancessignificantlyaffecttheacperformanceoftheADC).
Thelow-passfilterbetweentheoutputoftheAD698andtheinputoftheAD8615servestwopurposes:ItlimitstheinputcurrenttotheAD8615.
Itfilterstheoutputvoltageripple.
TheAD8615hasinternalprotectivecircuitrythatallowsvoltagesexceedingthesupplytobeappliedattheinput.
ThisisimportantbecausetheoutputvoltageoftheAD698canswing±11Vwith±15Vsupplies.
Aslongastheinputcurrentislimitedtolessthan5mA,highervoltagescanbeappliedtotheinput.
ThisisprimarilyduetotheextremelylowinputbiascurrentoftheAD8615(1pA)whichallowstheuseoflargerresistors.
Theuseoftheseresistorsaddsthermalnoise,whichcontributestotheoveralloutputvoltagenoiseoftheamplifier.
TheAD8615isanidealamplifiertobufferanddrivetheinputoftheAD799212-bitSARADCbecauseofitsinputovervoltageprotection,anditsabilitytoswingrail-to-railatboththeinputandoutput.
NoiseAnalysisWithallsignalconditioncomponentsselected,theamountofresolutionneededtoconvertthesignalmustbedetermined.
Asinmostnoiseanalyses,onlythekeycontributorsneedtobeidentified.
Noisesourcescombineinanrssmanner;therefore,anysinglenoisesourcethatisatleastthree-to-fourtimeslargerthananyoftheothersdominates.
InthecaseoftheLVDTsignalconditioningcircuit,thedominantsourceoftheoutputnoiseistheoutputrippleoftheAD698.
Theothersourcesofnoise(resistornoise,inputvoltagenoise,andoutputvoltagenoiseoftheAD8615)aresignificantlysmallerincomparison.
TheoutputvoltagerippleoftheAD698is0.
4mVrmswitha0.
39Fcapacitorvalueandwitha10nFshuntcapacitoracrossthefeedbackresistorshowninFigure3.
NotethatthesecomponentsandrelatedpinconnectionsarenotshowninthesimplifiedschematicinFigure1;however,detailscanbefoundintheAD698datasheet.
Figure3.
OutputVoltageRipplevs.
FilterCapacitanceThemaximumnumberofrmscountsthatcanberesolvedcannowbecalculatedbydividingthefull-scaleoutputbythetotalsystemrmsnoise.
TotalRMSCounts=5V/0.
4mV=12,500Theeffectiveresolutionisfoundbytakingthebase2logarithmofthetotalrmscounts.
EffectiveResolution=log2(12,500)=13.
6BitsNoise-freecoderesolutioncanbeobtainedbysubtracting2.
7bitsfromtheeffectiveresolution.
Noise-FreeCodeResolution=EffectiveResolution2.
7Bits=13.
6Bits2.
7Bits=10.
9BitsThetotaloutputdynamicrangeofthesystemcanbecalculatedbydividingthefull-scaleoutputsignal(5V)bythetotaloutputrmsnoise(0.
4mVrms)andconvertingittodecibels,yieldingapproximately82dB.
DynamicRange=20log(5V/0.
4mV)=82dBTheAD7992isagoodcandidateforthisapplicationbecauseithas12-bitresolutionandasamplingrateof188kSPSperchannelwhenusedwitha3.
4MHzserialclock.
10001001010.
10.
0010.
010.
111011607-003RIPPLE(mVrms)C2,C3,C4;C2=C3=C4(F)10kHz,CSHUNT=1nF10kHz,CSHUNT=10nFCN-0301CircuitNoteRev.
A|Page4of7CompensatingforPhaseLag/LeadTheAD698usesdemodulationtogenerateanoutputsignalbymultiplyingthereturnsignalwiththereferenceoscillatorfedtotheprimary.
Smallamountsofphaseshiftcanproducesignificantlinearityerrorwhichisseenasundershootintheoutput.
Thephaseleadnetworkcompensatesforthe3°ofprimarytosecondaryphaseshiftoftheE-100seriesLVDT.
Figure4showstwodifferentphasecompensationnetworks.
Figure4.
PhaseLag/LeadNetworkWhenchoosingcomponentvaluesfortheappropriatenetwork,itisimportanttonotethatRSandRTeffectivelyconstitutearesistordividerthatreducestheamplitudeoftheexcitationsignalsbeforeitreachesthe±ACOMPinputsoftheAD698.
ThissuggeststhatRTneedstobemuchlargerthanRS.
Thelag/leadcircuitryalsoaddsloadtotheexcitationoutputtherefore,largerresistivevaluesarerecom-mended.
Theendgoalistoachievethedesiredphaselag/leadontheACOMPinputsoftheAD698withasmallamplitudedrop.
Theamountofphaselag/leadcanbecalculatedbyusingthefollowingformulas:()CRHzLagPhase**=1tan**=CRHzLeadPhase1tan1whereTSSRRRR++=11Hz=ExcitationFrequencyTestResultsUsingaMeasurementSpecialties,Inc.
E-100EconomySeriesLVDTconnectedtoJ3andusingadigitaloscilloscopetomonitortheoutputoftheAD698foundonJ6ontheEVAL-CN0301-SDPZevaluationboard,theactualoutputripplefoundwas6.
6mVp-p,asisshowninFigure5.
Figure5.
OutputVoltageRippleBeforeLow-PassFilterThelow-passfilter(3k,0.
01F)betweentheAD698outputandtheAD8615inputhasa3dBbandwidthof5.
3kHzandreducestherippleto2mVp-p.
Withthelow-passfilterinstalledbetweentheoutputstageoftheAD698andtheinputstageoftheAD8615,datawascollectedfromtheEVAL-CN0301-SDPZevaluationboard,asshowninFigure6.
Figure6.
ScreenshotoftheCN-0301EvaluationSoftwareTheripplefromtheAD698wasattenuatedto2mVp-p,andthesystemwasabletoachieve11bitsofnoise-freecoderesolution.
Acompletedesignsupportpackageforthiscircuitnotecanbefoundathttp://www.
analog.
com/CN0301-DesignSupport.
ApplicationsinFlightControlSurfacePositionFeedbackUnmannedautonomousvehicles(UAVs),ordrones,areplayinganever-increasingpartinthenationalsecurityoftheUnitedStates.
Thesehightechnology,complexaerialplatformsarecontrolledbyacrewmilesawayandaremultimissioncapable.
Theyincluderolessuchasaerialreconnaissance,combatweaponsplatforms,battlefieldtheatercommandandcontroloversight,orunmannedin-flightrefuelingstation.
PHASELAGPHASELEADABCCRSRSRTDABCRTRSCCD11607-004CH12.
0mVM2.
000s111607-00511607-006CircuitNoteCN-0301Rev.
A|Page5of7ThecomplexsystemsemployedonUAVsuseamyriadofelectronicsensorsforprecisecontrolandfeedback.
Tocontrolthealtitude(pitch,roll,andyaw)oftheUAV,actuatorsareusedtoexertforcesontheflightcontrolsurfaces.
Theprecisemeasurementofthepositionoftheseactuatorsiscrucialinmaintainingtheproperflightofpath.
Thesensorsusedtomeasureactuatorpositionneedtomeetthreeessentialcriteria:highaccuracy,highreliability,andlightweight.
AllthreeoftheseattributesarefoundintheLVDTsdesignedbyMeasurementSpecialties,Inc.
SynchronousOperationofMultipleLVDTsInmanyapplications,suchasmultiplegagingmeasurement,alargenumberofLVDTsareusedincloseproximity.
IftheseLVDTsoperateatsimilarcarrierfrequencies,straymagneticcouplingcancausebeatnotestobegenerated.
Theresultingbeatnotesmayinterferewiththeaccuracyofmeasurementsmadeundertheseconditions.
Toavoidthissituation,allLVDTsoperatesynchronously.
TheEVAL-CN0301-SDPZevaluationboardcanbeconfiguredtohaveonemasteroscillatorbetweentwoLVDTsbypopulatingJumperJP1,JP2,andJP4withashortingjumperandleavingJP3unpopulated.
EachLVDTprimaryisdrivenfromitsownpoweramplifier,and,thus,thethermalloadissharedbetweentheAD698devices.
COMMONVARIATIONSThecomponentsselectedwereoptimizedforamaximum5VunipolaroutputfromtheAD698;however,othercombinationscanbesubstituted.
Othersuitablesingle-supplyamplifiersaretheAD8565andAD8601.
TheseamplifiersaresuitablereplacementsfortheAD8615becausetheyhaveinputovervoltageprotectionandtheabilitytoswingrail-to-railatboththeinputandoutput.
Ifdual-supplyoperationisrequired,theADA4638-1orADA4627-1issuggested.
IftheAD698outputs±10Vbipolarsignals,theAD7321issuggested.
TheAD7321isa2-channel,bipolarinput,12-bitADCthatcanaccepttruebipolaranaloginputsignalsaslargeas±10V.
CIRCUITEVALUATIONANDTESTThiscircuitusestheEVAL-CN0301-SDPZcircuitboardandtheEVAL-SDP-CB1ZSDP-Bsystemdemonstrationplatformcontrollerboard.
Thetwoboardshave120-pinmatingconnectors,allowingforthequicksetupandevaluationoftheperformanceofthecircuit.
TheEVAL-CN0301-SDPZcontainsthecircuittobeevaluated,andtheEVAL-SDP-CB1Z(SDP-B)isusedwiththeCN-0301EvaluationSoftwaretocapturethedatafromtheEVAL-CN0301-SDPZ.
EquipmentNeededThefollowingequipmentisneeded:APCwithaUSBportandWindowsXP(32bit),WindowsVista,orWindows7TheEVAL-CN0301-SDPZcircuitboardTheEVAL-SDP-CB1ZSDP-BcontrollerboardTheCN-0301EvaluationSoftwareTheEVAL-CFTL-6V-PWRZdcpowersupplyorequivalent6V/1AbenchsupplyMeasurementSpecialties,Inc.
,E-100EconomySeriesLVDT(EVAL-CFTL-LVDT)GettingStartedLoadtheevaluationsoftwarebyplacingtheCN-0301EvaluationSoftwareintotheCDdriveofthePC.
UsingMyComputer,locatethedrivethatcontainstheevaluationsoftware.
FunctionalBlockDiagramSeeFigure1forthecircuitblockdiagramandtheEVAL-CN0301-SDPZ-PADSSchematic.
pdffileforthecompletecircuitschematic.
ThePDFfilecanbefoundintheCN-0301DesignSupportPackage.
Figure7.
TestSetupBlockDiagramSetupConnectthe120-pinconnectorontheEVAL-CN0301-SDPZtotheCONAconnectorontheEVAL-SDP-CB1Z(SDP-B).
Usenylonhardwaretofirmlysecurethetwoboards,usingtheholesprovidedattheendsofthe120-pinconnectors.
Withpowertothesupplyoff,connecta6Vpowersupplytothe+6VandGNDpinsontheboard.
Ifavailable,a6Vwallwartcanbeconnectedtothebarrelconnectorontheboardandusedinplaceofthe6Vpowersupply.
ConnecttheUSBcablesuppliedwiththeEVAL-SDP-CB1ZtotheUSBportonthePC.
DonotconnecttheUSBcabletotheMini-USBconnectorontheEVAL-SDP-CB1Zatthistime.
TestApplypowertothe6Vsupply(orwallwart)connectedtotheEVAL-CN0301-SDPZ.
LaunchtheevaluationsoftwareandconnecttheUSBcablefromthePCtotheMini-USBconnectorontheEVAL-SDP-CB1Z.
WhenUSBcommunicationsareestablished,theEVAL-SDP-CB1Zcansend,receive,andcaptureparalleldatafromtheEVAL-CN0301-SDPZ.
Figure8showsaphotooftheEVAL-CN0301-SDPZconnectedtotheEVAL-SDP-CB1Z.
InformationregardingtheEVAL-SDP-CB1ZcanbefoundintheUG-277UserGuide.
120PINSJ4J1J8EVAL-CN0301-SDPZBOARDMEASUREMENTSPECIALTIES,INC.
E-100ECONOMYSERIESLVDTEVAL-CFTL-LVDTEVAL-SDP-CB1ZSDP-BBOARDUSBCONAEVAL-CFTL-6V-PWRZ6VWALLWARTPC11607-007CN-0301CircuitNoteRev.
A|Page6of7Informationanddetailsregardingtestsetupandcalibration,andhowtousetheevaluationsoftwarefordatacapturecanbefoundintheCN-0301SoftwareUserGuide.
ConnectivityforPrototypeDevelopmentTheEVAL-CN0301-SDPZisdesignedtousetheEVAL-SDP-CB1Z;however,anymicroprocessorcanbeusedtointerfacetotheI2C2-wireserialinterfaceoftheAD7992.
InorderforanothercontrollertobeusedwiththeEVAL-CN0301-SDPZ,softwaremustbedevelopedbyathirdparty.
ThereareexistinginterposerboardsthatcanbeusedtointerfacetotheAlteraandXilinxfieldprogrammablegatearrays(FPGAs).
TheBeMicroSDKboardfromAlteracanbeusedwiththeBeMicroSDK/SDPinterposerusingniosdrivers.
AnyXilinxevaluationboardthatfeaturestheFMCconnectorcanbeusedwiththeFMC-SDPinterposerboard.
TheEVAL-CN0301-SDPZisalsocompatiblewiththeDigilent,Imodinterfacespecification.
AphotoofthesystemisshowninFigure8.
Figure8.
TheEVAL-CN0301-SDPZBoardConnectedtoEVAL-SDP-CB1Z(SDP-B)BoardandMeasurementSpecialties,Inc.
,E-100EconomySeriesLVDTUSBEVAL-CN0301-SDPZEVAL-SDP-CB1ZEVAL-CFTL-6V-PWRZMEASUREMENTSPECIALTIES,INC.
E-100ECONOMYSERIESLVDTEVAL-CFTL-LVDT11607-008CircuitNoteCN-0301Rev.
A|Page7of7LEARNMORECN-0301DesignSupportPackage:http://www.
analog.
com/CN0301-DesignSupportSDP-BUserGuideArdizzoni,John.
APracticalGuidetoHigh-SpeedPrinted-Circuit-BoardLayout.
AnalogDialogue39-09,September2005.
MT-004Tutorial,TheGood,theBad,andtheUglyAspectsofADCInputNoise—IsNoNoiseGoodNoise,AnalogDevices.
MT-031Tutorial,GroundingDataConvertersandSolvingtheMysteryof"AGND"and"DGND",AnalogDevices.
MT-035,OpAmpInputs,Outputs,Single-Supply,andRail-to-RailIssues,AnalogDevices.
MT-036Tutorial,OpAmpOutputPhase-ReversalandInputOver-VoltageProtection,AnalogDevices.
MT-068Tutorial,DifferenceandCurrentSenseAmplifiers,AnalogDevices.
MT-101Tutorial,DecouplingTechniques,AnalogDevices.
AN-1106ApplicationNote,AnImprovedTopologyforCreatingSplitRailsfromaSingleInputVoltage,AnalogDevices.
E-100EconomySeriesLVDT,MeasurementSpecialties,Inc.
TheLVDT:constructionandprincipleofoperation,TechnicalPaper,MeasurementSpecialties,Inc.
,1000LucasWay,Hampton,VA23666.
SubminiatureLVDTsProvideAccurateFlightControlSurfacePositionFeedbackonUAVs,ApplicationNote,MeasurementSpecialties,Inc.
,1000LucasWay,Hampton,VA23666.
DataSheetsandEvaluationBoardsCN-0301CircuitEvaluationBoard(EVAL-CN0301-SDPZ)SystemDemonstrationPlatform(EVAL-SDP-CB1Z)AD698DataSheetAD7992DataSheetAD8615DataSheetADP1613DataSheetADP7104DataSheetREVISIONHISTORY3/14—Rev.
0toRev.
AChangestoSynchronousOperationofMultipleLVDTsSection.
.
.
.
.
55/13—Revision0:InitialVersion(Continuedfromfirstpage)CircuitsfromtheLabreferencedesignsareintendedonlyforusewithAnalogDevicesproductsandaretheintellectualpropertyofAnalogDevicesoritslicensors.
WhileyoumayusetheCircuitsfromtheLabreferencedesignsinthedesignofyourproduct,nootherlicenseisgrantedbyimplicationorotherwiseunderanypatentsorotherintellectualpropertybyapplicationoruseoftheCircuitsfromtheLabreferencedesigns.
InformationfurnishedbyAnalogDevicesisbelievedtobeaccurateandreliable.
However,CircuitsfromtheLabreferencedesignsaresupplied"asis"andwithoutwarrantiesofanykind,express,implied,orstatutoryincluding,butnotlimitedto,anyimpliedwarrantyofmerchantability,noninfringementorfitnessforaparticularpurposeandnoresponsibilityisassumedbyAnalogDevicesfortheiruse,norforanyinfringementsofpatentsorotherrightsofthirdpartiesthatmayresultfromtheiruse.
AnalogDevicesreservestherighttochangeanyCircuitsfromtheLabreferencedesignsatanytimewithoutnoticebutisundernoobligationtodoso.
2013–2014AnalogDevices,Inc.
Allrightsreserved.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
CN11607-0-3/14(A)
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