Isolated 16-Channel AC Analog Input Module Reference Design Using Dual ADCs

38 Pages·2017·1.05 MB·English

Design Guide: TIDA-01576
High-Accuracy Analog Input Module Reference Design
With 16-bit 1-MSPS Dual Simultaneous-Sampling ADC
Description Features
Thisreferencedesignprovidessolutionforaccurate • ThedesignshowcasesdesignofACanaloginput
measurementof 16-channelwideACanaloginputs moduleusingADS8688S,16-channel16-bit1-
(voltageandcurrent)usingprecision16-channel16-bit MSPSdualsimultaneous-samplingADCWith
1-MSPS dualsimultaneous-samplingADCcovering IntegratedAnalogFront-End
protectionandmeasurementrequirements(including • Accuracytestingdonebyinterfacing
samplingrequirementsasperIEC61850-9-2) ADS8686SEVM-PDKtoAFEwithvoltageand
simplifyingsystemdesign,improvingtriptime currentsensors,gainscalingamplifiersandsplit-
performanceandreliability.Coherentsamplingofthe railpower suppliesintegratedon-board
analoginputswithconfigurablesamplespercycles
• Optionfor programmablelow-passfilter(15 kHz,
andprogrammableoversamplingrateimproves
39kHz,376kHz) improvessystem performance
measurementperformance.Thereferencedesign
anddesignflexibility
performancehasbeentestedoverwidetemperature
rangewithinternal orexternalreferenceconfigured • OptiontoconfigureADCtomeasure20%
andnoappreciablevariationinerrorwasobserved. overrangeimprovesdynamicrangewithout
ThealarmfeatureidentifiestheACAIMfaultsona affectingmeasurementaccuracy
samplebasisforfasterfaultdetection.ADS8688A • Digitalsupplyrangeof1.8Vto5Vminimizesuse
ADChasanadditionalauxiliary channeltodiagnose ofexternallogic
theoutputofthedigital isolatorsupplyorto
• Gainscalingamplifiersusedincludesprecisionop
compensatethemeasuredanaloginputsfor
ampandinstrumentationamplifiersproviding
temperaturedrift.
designflexibility
Resources • Measurementaccuracyobservedtobewithin
±0.2%for ACvoltageinput rangeof10Vto 425V
andVariationinmeasurementaccuracyobserved
TIDA-01576 DesignFolder
tobewithin±0.3%for ACcurrent input range of 1A
ADS8686S,REF5025 ProductFolder
to120A
ADS8688A,ADS8688 ProductFolder
INA188,OPA2188 ProductFolder • Variationinmeasurementerrorobservedto be
within±0.1%over-15to+80°C
ISO7763,ISOW7841 ProductFolder
SN6505B,TPS65131 ProductFolder • Optionally,isolatedinterfacebetween
TLV2171,TPS3840 ProductFolder ADS8686SEVM-PDKandthehostPHIcontrolleris
TPS7A39,TPS7A47 ProductFolder showcasedfor improvedperformanceandsafetyin
harshoperatingconditionusingdigitalisolatorwith
LMT70,LM35 ProductFolder
externalisolatedDC/DCbasedpower supply.No
UCC12050,UCC12040 ProductFolder
changeintheADCperformanceobserved.
LM2903,OPA188 ProductFolder
REF6041,REF5040 ProductFolder
Applications
ISO7820,REG71055 ProductFolder
• MultifunctionProtectionRelay
TPS79101,TPS7A4901 ProductFolder
• SubstationBayController
• Stand-AloneMergingUnit(SAMU)
• RTU,FTU,DTU,orFRTU
SearchOurE2E™supportforums
• PLCfor FactoryAutomation
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10-350 V AC Input ±12 V
OPA2188 Gain 5.6+ 12 V 3.3 VPD_OUT1 T2
Common ±12 VREF LM2903 ZCD
+ ZCD
J17, Pin 15
INA188 Gain 7.175 PD_OUT2
10-350 V AC Input ±12 V
OPA2188 Gain 5.6 PD_OUT3 T3
24 V Common INA±11828 V±12VGain 7.175 PD_OUT4 J17 PHI bcooanrtdroller
TVS3300 ±12 V
TVS3300 1.5-150A OPA2188 Gain 10 ±12 V CT_1_OUT T4
5 V LM74700Q LMZ14201 REF6241 OPA188 Reference
5 V INA188 Gain 7.175 CT_1_OUT
TLINVA1313137ALVID33 TTPPSS76A53193011 + 12 V LMT70 INA±11828 V Temperature T5
3.3 V Gain 7.175 -
ADS8686SEVM - PDK
1
AnIMPORTANTNOTICEattheendofthisTIreferencedesignaddressesauthorizeduse,intellectualpropertymattersandother
importantdisclaimersandinformation.
1 System Description
Powersystemfailuresisoneofthecommon problemsfacedbypower generation,transmission,and
distributioncompanies.Poweroutagesresultinlossofrevenueandreducesgenerationcapacity.Power
utilitiesareworkingtowardsprovidingreliablepower byusingsecondaryprotection, control,monitoring,
andmeasurementsystemstothepower systemsefficiencyandreliability.
1.1 Introduction to Protection Relays
Digitalprotectionrelaysdetectdefectivelines,equipment,orotherpower systemconditionsthatare
abnormalordangerousinnature.Digitalprotectionrelaysdetect andlocatefaultsbymeasuringelectrical
quantitiesinthepowersystem,whichisdifferent duringnormalandintolerableconditions. MeasuringAC
voltageandcurrentinputsaccuratelyoverawideinput rangeiscriticalfor thedigitalprotectionrelays.The
majorfunctionalcomponentsofadigitalprotectionrelayincludedataacquisition(analogfilteringand
sampling),measurement(phasorestimation),andlogic(tripping,alarming, carriersend,andsoon).
1.1.1 MultifunctionProtectionRelayforGeneration,Transmission,orDistributionApplications
ThekeyinputsforthefunctioningoftheprotectionrelayareACvoltagesandcurrents.Most ofthe
protectionalgorithmsarebasedontheamplitude, frequency,andthephaseoftheACvoltagesand
currents.TheACAIMcapturestheoutput ofthevoltageandcurrenttransformersconnectedacrossthe
equipmentbeingmonitored.Dependingonthemonitoredequipmentandtheprotectionfunction
configured,thenumberofanaloginputscanbe4,8,12,or16.
1.1.2 Stand-AloneMergingUnit
Themergingunitcapturesthevoltageandcurrent inputsfromtheequipmentitconnectstoandprovides
thedigitaldatatodifferentIEDsusingIEC61850-9-2protocol.Dependingonthemonitoredequipment,
thenumberofanaloginputscanbe4,8,12,or16.
1.1.3 SubstationBayControllerandTerminalUnit
Thebaycontrollermonitorsanaloganddigitalinputsfromdifferent primaryequipmentsconnectedon the
bayinasubstation.Thenumberofanaloginputsdependsonthebaycontroller configurationandcan
varyfrom8to24.
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1.2 Key System Specifications
Table1showsthekeysystemspecificationsfor thehigh-accuracy,16-channelAIMreferencedesign.
Table1. KeySystemSpecifications
SERIAL
PARAMETER DESCRIPTION COMMENT
NUMBER
16-bitSARADCwithconfigurableinput
1 ADC SPI
ranges
16channelswithdualsimultaneous
2 Numberofchannels
sampling
3 Inputrange 10V,5V,2.5V Withprogrammable20%overrange
MeetsIEC61850-9-2sampling
requirementsforprotectionand
4 Samplingrate 1-MHz measurement.Provides
programmableOSRforperformance
improvement.
5 Inputimpedance Constant1-MΩinputimpedancefront-end
6 Digitalisolatorwithintegratedpower Reinforced
Digitalisolation Six-channeldigitalisolatorwithexternal Reinforced,providesflexibilityin
7
isolatedpower digitalisolatorselection
Programmablefilterof15kHz,39kHzor
8 internalfiler
376kHz
PotentialdividerinterfacedtoPrecision Withdifferentgainstocoverwide
9
amplifierandinstrumentationamplifier inputs
AFE
CurrentsensorinterfacedtoPrecision Withdifferentgainstocoverwide
amplifierandinstrumentationamplifier inputs
Serialinterfacesimplifies
10 SPI
communicationinterface
Hostinterface
Parallelinterfacereducesfirmware
11 Parallel
complexity
Digitalandanalogpowersupplyusing
12 DisplayedonGUI
auxiliarychannels
Diagnostics
LEDindicationforalarm,power,andactivity
13 Visualindication
(chipselect)
14 Split-railsupplywithLDO Outputprogrammable,lowripple
Powersupply IsolatedpowersupplyusingisolatedDC/DC
15 Efficiency>60%
ortransformerdriver
Onboardanalogtemperaturesensorfor
Temperature
16 compensationmeasurementaccuracy Accuracy<±0.2%
compensation
variation
17 Analoginputconnectors Screwtypeconnector
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2 System Overview
ThisreferencedesignaccuratelymeasuresACvoltageandcurrent inputsusingaprecision16-bit
successiveapproximation(SAR)analog-to-digitalconverter(ADC)overawideinput rangecovering
protectionandmeasurementapplications(includingsamplingrequirementsasperIEC61850-9-2),
simplifyingsystemdesignandimprovingtriptimeperformanceandreliability.Twoapproachesfor
designingofAIMhavebeenshowninthisreferencedesign. Thefirstapproachisusinga16-channel16-
bitSARdualsimultaneoussamplingADC.Thesecondapproachisusingtwo8-channel16-bitADCs
connectedtogethertoincreasethenumberofanaloginput channelsto16usingdaisychainmode ordual
SDO outputmodewiththecontrolinput signalsconnectedtogether anddrivenbycommon pins.The AIM
isisolated fromthehostprocessorusingadigitalisolatorwithanintegratedpower converter.Acomplete
ACAIMcanbedesignedusingonlyTIproducts, optimizingsystem costandsize. Thealarmfeature of
ADS8688AidentifiestheACanaloginputfaultsonasamplebasisfor fasterfaultdetection.The
ADS8688AADChasanadditionalauxiliarychanneltodiagnosethesupplyoutputofthedigitalisolator.
2.1 Block Diagram
Thisreferencedesignshowcasesthefollowingconfigurationsfor improvedsystemperformance:
• 16-bitADCADS8686Sbased16-channelanaloginput module
• 16-bitADCADS8686Sbasedisolatedinterfacemodule
• ADS8688A-based,16-channelinput withdualSDOfor measurementofACorDCanaloginput
• ADS8688A-based,isolated,16-channelinput withdualSDOusingdigitalisolatorswithintegrated
power
Thearchitecturechoicedependsonthesize,input rangeandneedfor alarmfeatures.
2.1.1 ADS8686Sbasedanaloginputmodule
ThesectionprovidessummaryofACanaloginput modulebasedonADS8686S.Theadvantageof
ADS8686SbaseddesignisintegrationoftwoADCsintoasingledevice, provisionfor serialorparallel
interfaceandprovisionforimplementingcoherentsampling.Extensionofanaloginput channelsbeing
measuredisrequiredformultifunctionsecondarygridequipmentsfor increasingthemeasurement
dynamicrange,diagnostics,featureenhancement,performanceoptimizationandformfactorreduction.
2.1.1.1 16-bitADCADS8686Sbased16-channelanaloginputmodule
TheADS8686Sbased16-channelACanaloginput moduleconsistsoftheanalogfront endboard withthe
potentialdivider,currenttransformer,signalscalingamplifiers, zerocrossdetectioncomparatorsandsplit
railsupplies.TheAFE isinterfacedtotheADS8686SEVM-PDKfor performanceevaluation.Themodule
hasthefollowingfunctionalblocks:
• PotentialdividertoscaletheACinput voltageandCurrenttransformer totransformtheprimarycurrent
tosecondarycurrent
• Gainscalingamplifiertoscalethesensoroutput toADCinput rangeusingprecisionop-ampor
instrumentationamplifiers
• Onboardstablereferenceandhighaccuracytemperaturesensorfor measurementreferencing and
benchmarkingduringtemperatureperformancetests
• ZerocrossdetectorforimplementingcoherentsamplingusingPHIcontroller(Digital)
• Split-railpowersupplywithdualLDOfor poweringthegainscalingamplifiers
• InterfaceconnectortoconnecttheoutputoftheAFEboardtoADS8686SEVM
• PHI controllerboardtoconnecttheADS8686SEVM-PDKtoGUIfor performanceevaluation
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10-350 V AC Input ±12 V
Gain 5.6 PD_OUT1
OPA2188
12 V T2
+ 3.3 V
Common ±12 V REF LM2903 ZCD
+ ZCD
J17, Pin 15
INA188
Gain 7.175 PD_OUT2
10-350 V AC Input ±12 V
Gain 5.6 PD_OUT3
OPA2188
T3
±12 V PHI controller
Common J17 board
±12V
PD_OUT4
24 V INA188
Gain 7.175
TVS3300 ±12 V
T4
Gain 10 CT_1_OUT
OPA2188
TVS3300 1.5-150A ±12 V
REF6241 OPA188
5 V
Reference
LM74700Q LMZ14201
INA188
5 V Gain 7.175 CT_1_OUT
±12 V T5
TLV1117LV33 TPS65131
+ 12 V
INA333AID TPS7A3901 Temperature
LMT70 INA188
Gain 7.175
3.3 V -
ADS8686SEVM - PDK
1
Figure1.IsolatedinterfacemoduleforADS8688SEVM-PDKandPHIcontrollerinterface
2.1.1.2 16-bitADCADS8686Sbasedisolatedinterfacemodule
TheisolatedinterfacemoduleisusedtoisolatethePHIcontroller interfacefromtheADS8686SEVM-PDK
based16-channelACanaloginputmoduleandhasthefollowingfunctionalblocks:
• Highspeeddigital isolatorforisolatingthesignalsbetweenthePHIinterfaceboardand
ADS8686SEVM-PDK
• InterfaceconnectorprovisiontomounttheADS8686SEVM-PDKononesideoftheboardandthePHI
controllerontheothersideoftheboard
• Provisiontogeneratesplit-railisolatedsuppliesusingtransformer drivertopower thegainscaling
amplifiers
• Provisiontogenerateisolatedsupplyfor ADCusinghighefficiencyisolatedDC/DCconverter
• Provisiontogeneratesplitrailisolatedsupplyfor gainscalingamplifiersusingtransformer driverand
dualLDO
• Zerocrossdetectorforimplementingcoherentsampling
• ProvisiontoconfiguretheADCusingjumpersettingontheinterfaceboardandADS8686SEVM-PDK
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Isolated side – ADS8686SEVM – PDK Interface Non-Isolated side – PHI Controller
Power
±12 V_I ±12 V_I
3.3 V_I
±12 V_I TPS7A39 SN6505B
OPA2171 LM2903 SN74LVC1G32 5 V
TPS7A4700
Internal RC ZCD_OUT_1 3.3V_I TPS7A4700 SN6505B +3.3 V
for RESET
5 V
3.3 V_I SN74LVC1G17
Jm8o, uJn9ted 5.4 V_OK TPS3897 5 V SorE 5L.4 V UCC12050 Sync_OK Jm3o,unted R243GAG32EF2VT-
ISO_SRESETn
3.3 V_I 3.3
ISO_BUG_SCLK SCLK
ISO_BUF_CSn CSn
ISO_SRESETn ISO7763 SRESETn
ISO_BUF_SYSCLK SYSCLK
T2 ISO_BUF_SDOA SDOA
ZCD_OUT_1 ZCD_OUT
XA n1a6l ocgh aInnpnuetlss T3 ADS8686SEVM-PDK J2 J1 PH ConBtrooallredr
T2 3.3 V_I 3.3 V
ISO_BUF_CONVST CONVST
T3 ISO_BUF_SDI SDI
EVM Jumper Configuration ISO_TBD ISO7763 TBD
JP1:chseIO – High J18:11, J18:10, J18:9 - Low ISO_BUF_SDOB SDOB
JJPP35::cchhsseeII12 –– HHiigghh ISO_BUF_BUSY BUSY
5.4 V_OK ZCD_OUT_1
SN74LVC1G17
Figure2.Isolated_ADS8688S_EVM_AFE_PHI_interface_module
2.1.2 ADS8688/ADS8688Abasedanaloginputmodule
ThissectionprovidesdetailsofdifferentapproachestodesignofACorACanaloginput moduleusing8-
channel16-bitADS8688/ADS8688AADC.AdvantagesofusingADS8688Aincludeavailabilitymultiple
inputranges,capabilitytomeasureunipolarandbipolarandoptiontoprogramalarms.Thisdesigncan be
usedforACorDCanaloginputmodulesandisscalablefrom4channelsto16channels.
2.1.2.1 ADS8688A-Based,16-ChannelACAIMWithDualSDO
TheADS8688A-based,16-channelACAIMwithdualSDOhasthefollowingfunctionalblocks:
• 2× ADS8688AADCsconnectedtogether tosample16channelsofACanaloginput witha ±10.24-V
inputrange
• ExternalreferenceforimprovingmeasurementaccuracybetweentwoADCs
• LDOstogeneratetherequiredanaloganddigitalpower supply
• HostinterfacewithdualSDOoutputs
• LEDsdrivenbyMOSFETforAlarmindication
• HostinterfaceandGUIforevaluatingtheperformanceoftheADC
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REF5040 TPS70950
Reference LDO
5.5 V
TPS70933
REFIO I_AVDD_5V I_DVDD_3.3
/CS to ADC1 and ADC2
1
. ADC1 SCK to ADC1 and ADC2
8 ADS8688
±10-V I_DVDD_3.3V 9 ADC1 and ADC2 SPI Breakout
analog SDI, /CS, SCK
input 10 connected together SDI to ADC1 and ADC2
. ADC2
17 ADS8688 SDO_ADC1
Diag1 18 SDO_ADC2
Daisy_Disabled Interface to GUI
Alarm × 2
CSD17571Q2 × 2
Diag1
LED drive
LM35
Temperature sensor
Figure3.ADS8688A16-BitSARADC-Based16-ChannelACAIMWithDualSDOOutput
2.1.2.2 ADS8688A-Based,Isolated,16-ChannelACAIMWithDualSDOusingDigitalIsolatorWith
Integrated Power
TheADS8688A-based,isolated,16-channelACAIMwithadualSDO, digitalisolator, andintegrated
powerblockdiagramhasthefollowingfunctionalblocks:
• ADS8688A-based,16-channelinput withdualSDOtomeasureACorDCanaloginputswitha ±10.24-
Vinputrange
• Hostinterfaceisolationprovidedusingfour-channeldigitalisolator withintegratedpower andtwo-
channeldigitalisolator
• ProvisionforSCKLloopbackfromtheADCsidetothehostsidefor improvedperformance
• DC/DCconverterandLDOtoprovidetherequiredanaloganddigitalpower supplytothemodule
• Analogtemperaturesensortocompensatethemeasurementerrorduetoambienttemperature
variation
• ReferencewithintegratedbufferforprovidingexternalreferencetotheADCsfor improved
performance
• HostinterfacetoevaluatetheperformanceoftheADCusingaPHIcontroller andGUI
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DC/DC
REG71055D
TPS3836K33
REF6041 TPS79101D
DVDD_3.3V
Reference LDO
REFIO
I_AVDD_5V I_DVDD_3.3
Analog inputs
SDO-ADC1
1
. ADC1 SCK_R ISO7820
8 ADS8688A
±10-V I_DVDD_3.3 9 Breakout
ADC1 and ADC2
analog daisy chained SDI
input 10
. ADC2 SDO_ADC2
17 ADS8688A SCK ISOW7841
Diag1 18
/CS
ADC
SPI Digital isolator
Daisy_Disabled with integrated Interface to GUI
Alarm × 2 power
CSD17571Q2
Diag1
LED drive
LMT70
Temperature sensor
Figure4.ADS8688A16-BitSARADC-Based,Isolated16-ChannelACAIMWithISOW7841andDualSDO
2.2 Design Considerations
2.2.1 ACCurrentandVoltageMeasurementModule
ThedataacquisitionfunctionintheprotectionrelayisperformedbytheACAIMandconsistsofthe
followingsubsystems.
2.2.1.1 CurrentSensorInput
Currentmeasurementsensorsthatcanbeusedincludecurrent transformers, shunts,Rogowskicoils,Hall
effect orfluxgatecurrentsensors,opticalcurrenttransformers,orlow-powercurrent transformers
(LPCTs). Inapplicationsusingshuntfor currentsensing, therequiredisolationisprovidedbythe isolation
amplifier orisolateddelta-sigmamodulator.
2.2.1.2 VoltageSensor Input
Voltagemeasurementsensorsthatcanbeusedincludepotentialtransformers,potentialdividers,or
capacitor voltagetransformers.Inapplications,usingpotentialdividerfor voltagemeasurement,the
requiredisolationcanbeprovidedbytheisolationamplifierorisolateddelta-sigmamodulator.
2.2.1.3 SignalConditioning
Asignalconditioningcircuitisusedtoscalethevoltageorcurrent sensoroutput totheADCrange.A
signalconditioningcircuitdependsonitsapplication.Thecircuit canbeaprecisionoperationalamplifier,
instrumentationamplifier,programmablegainamplifier, oradifferentialorisolationamplifier. Theamplifier
selectiondependsontheaccuracyandtemperaturedriftrequirements.
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2.2.1.4 HostInterface
TheADCisinterfacedtoahostthatcapturesthedigitalvaluesfromtheADCandcomputestheelectrical
parametersusedforprotection,measurement,andcontrolandmonitoringapplications.
2.2.1.5 ADC
Accuratemeasurementsofvoltageandcurrent inputsarekeyperformancerequirementsfor grid
infrastructureapplications.SelectinganADCiscriticaltothedigitalprotectionrelayperformance, andthe
measurementaccuracyforprotection,monitoring,andcontroldependsontheADCselection.Key
performanceparametersforADCselectionincludeADCarchitecture,ADCresolution,ADCinputsampling
method,ADCinputtypeandrange,ADCpower supply, clock,andreference.AnotherimportantADC
requirementisscalingthesamplingratetomeetIEC61850-9-2standardsfor bothprotectionand
measurement.
2.2.2 Needfor Isolation,Challenges,andSolutions
Powersystemequipmentthatfailareresponsiblefor alargeproportionofpower systemoutagesand
associatedinterruptionofelectricitysupplytocustomers.Othercausesofinterruptionincludeextreme
weatherconditions,amongothers.Iffailurescanbepredictedbeforetheyoccur, actioncanbetakento
reducetheoccurrenceofunplannedoutagesofequipment,thuscontributingtomeetingperformance
targetsandreducingthecostofinterruptions.Theinputsareisolatedusinganisolationamplifier,isolated
delta-sigmamodulators,orcurrentorpotentialtransformers.Someofthecommonrequirementsfor
isolationofanACAIMincludeisolationtype(basicorreinforced),jitterinpS,power supplyintegrated with
anisolatororexternal,andthenumberofchannelsfor anI2C,SPI, orUARTinterface.
2.2.3 ReferenceDesignAdvantage
ThisreferencedesignusesADS8686S(16-channel)orADS8688A(withdaisychainedorwithDualSDO
output)andprovidesthefollowingadvantagesduringthedesignofACorDCanaloginput module:
• Provisiontomeasure16channelsof analoginputswithprogrammableinput ranges
• Provisionforprogrammableinputrangesof±10V, ±5Vand ±2.5Vwith20%overangeand
programmablefiltersimprovessystemperformance
• Digital:1.8Vto5Vsupplyrangeprovidesdesignflexibilityandminimizesuseofexternallogic
• ProvisiontoimplementcoherentsamplingandprogramOSRfurtherimprovessystemperformance
• Availabilityofserialorparallelhostinterfaceprovidesadditionalsystemdesignflexibility
• BidirectionalInputsupto±10.24Vcanbemeasuredusingasingle5Vanalogsupply
• Availabilityofserialorparallelhostinterfaceprovidesadditionalsystemdesignflexibility
• Gainscalingamplifierandsplitrailpower supplyontheAFEcanbefullyreusedreducingdesigntime
• Providesreinforcedisolationoftheinterfaceusingdigitalisolatorwithintegratedpower ordigital
isolatorwithexternalisolatedpower
• Simplifiesoveralldesignbyuseof6channeldigitalisolator ina16-Pinpackage
• MeetsADCdynamicspecificationincludingENOB,SNR,andTHDwithisolatedinterface
• Providesisolationoftheinterfaceusingadigitalisolatorwithintegratedpower orexternalisolated
power
• Providesoptionsforpowersupplydiagnostics(analoganddigitalsupply) andalarmindication
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2.3 Highlighted Products—System Design
2.3.1 ADS8686SADC
Useof16-channelADCwithdualsimultaneoussamplingcapabilitysimplifies designinapplications
requiringextensionofanaloginputchannels. SomeofthekeyfeaturesofADS8686Sinclude
• 16-channel,16-bitADCwithintegratedanalogfront-end
• Dualsimultaneoussampling:8x2channels
• SupplyincludesAnalog:5VandDigital:1.8Vto5V(noleveltranslator requiredfor 1.8Vsystems)
• Independentlyprogrammableinputrangeswith20%overrange
• Programmablelow-passfilter –15kHz,39kHz,376kHz
DVDD
C1 C2
10uF 0.1uF DVDD
AVDD
U1 R1
GND 10.0k
Place pGaiNr DofC1 d30eucFouplingC0 4c.1aupFsC1 n10e1uaFr C1e50auchF CA01.V12DuDFC0 d6.1euviFce pRinECF1I70NuOFUT C08.1uF CAABBAAAAAAAAAAAAAABBBBBBBBBBBBBB190IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIINNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNu00112233445566770011223344556677FGGGGGGGGGGGGGGGGC0NNNNNNNNNNNNNNNN1.13DDDDDDDDDDDDDDDDuFC01.10uF REFSEL 11111111222222223334777777778123702347589023456780359034567890234678911111 VVVVVVVVVVVVVVVVVVVVVVVVVVVRRRVRVVVVVVVVVEEEE44556677776655443322110000112233CCCDCFFFGBBBBBBBBAAAAAAAAAAAAAAAABBBBBBBBCCCCRCISGGGGGGGGGGGGGGGGCINEVAANNNNNNNNNNNNNNNNOLEPPDDDDDDDDDDDDDDDDUT RHHEWFWDIDDDNW__BRBBBORDDRD4E5R11RSDSNRUNBBC/GB/12/ECCECSCBEGCO11TBG1SG//RRGHHLEHF135RGSSES4UNKSAAAA/ENRBGGSS0//SDDECQ/PEN/RSVGGGG1EEUOO/DENNOLERODDDDDDDAOLEEDSSDLLWSNNNNL0SSSDN1DDDCSTRNBBBBBBB02TDBATB1Y02DDDD1S0236789I1 3651275543544444556656663436665334564676929769113478345180388224696470525 GND1R0109kDDDDDDSCDDDDDCS__BBBB___BBLHHCBCCC111111KO1235UHHH04WW///////SSSSNRSSOOSO__EEEYDVDDDRRSSLLLSSOONNI012021TBAGGSSEELL01 GGNNDD1R1R0017007kkSEQ1R1R01E0803N0kkD1RV09D0DZkZ5As1Rse01m00kbGlyN ND1Ro010t81Rek0101k1RW01R04/k1RB01U02RkDSVTDD DDRDDDDDDEBBBBBBBBS09123678E//TBFLYTTEENSEL GND1R02.0k SER/PAR/BY1R1R1R1RT00005321E000005kkkkDDGGVVNNDDDD1R1R1R1RDD00006421000016kkkk DDDDBBBB9458////BSCFELYRTRTCEE1ENSWNEL
GND GND C1104uF 52 REGCAPD DGND 50 On JP1 through JP5 place jumper short on pin2-3
ADS8686-PZA DVDD
C15 C16 JP1
GND 10uF 0.1uF GND DVDD CHSEL0 123 1R0202k D_CHSEL0
JP2
GND HW_RNGSEL0 123 GND1R0203k D_HW_RNGSEL0 CHSEL1 JP3 123 DGVNDDD 1R0204k D_CHSEL1
JP4 DVDD GND
INT JP6 D1VDD ZZ6 HW_RNGSEL1 123 1R0205k D_HW_RNGSEL1 CHSEL2 JP5 123 DVDD 1R0206k D_CHSEL2
REFSEL 2 REFSEL Assembly Note GND
EXT R27 On JP6 place jumper short GND
10.0k
GND
Figure5.SchematicsofADS8686SADCconfigurationfor16Analoginputs
2.3.1.1 ADS8686S
TheADS8686Sisa16-channeldataacquisition(DAQ)systembasedonadualsimultaneous-sampling,
16-bitsuccessiveapproximationregister(SAR)analog-to-digitalconverter (ADC).TheADS8686Sfeatures
acompleteanalogfront-endforeachchannelwithaninput clamp,1-MΩ input impedance,independently
programmablegainamplifier(PGA),programmablelow-passfilter,andanADCinput driver.Thedevice
alsofeaturesalow-drift,precisionreferencewithabuffer todrivetheADCs.Aflexibledigitalinterface
supportingserial,parallel,andbytecommunicationenablesthedevicetobeusedwithavarietyofhost
controllers.TheADS8686Scanbeconfiguredtoaccept ±10-V, ±5-V,or±2.5-Vbipolarinputswitha20%
overrangeoptionusingasingle5-Vsupply.Thehighinput impedanceallowsdirectconnectionwith
sensorsandtransformers,thuseliminatingtheneedfor externaldrivercircuits.TheADS8686Shasa
highlyconfigurablechannelsequencertoreducethesequencingoverheadonthebackendcontrolleror
processor.Thehighperformanceandaccuracy,alongwithzero-latencyconversionsofferedbythisdevice
maketheADS8686Sagreatchoiceformultipleindustrialapplications.
10 High-AccuracyAnalogInputModuleReferenceDesignWith16-bit1-MSPS TIDUDP7A–December2017–RevisedApril2020
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