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ADS8681,ADS8685,ADS8689
ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016
ADS868x支持可编程双极输入范围的16位高速单电源SARADC数据采集系统
1特性
•1集成模拟前端的16位ADC•高速：
–ADS8681：1MSPS–ADS8685：500kSPS–ADS8689：100kSPS•可通过软件编程的输入范围：–双极范围：±12.288V、±10.24V、±6.144V、±
5.12V和±2.56V–单极范围：0V–12.288V、0V–10.24V、0V–
6.144V以及0V–5.12V•5V模拟电源：1.65V到5VI/O电源•恒定的阻性输入阻抗≥1MΩ•输入过压保护：高达±20V•低漂移的片上4.096V基准电压•出色的性能：
–DNL：±0.4LSB；INL：±0.5LSB–SNR：92dB；THD：–107dB•ALARM→每通道的高低阈值•multiSPI™接口，支持菊花链连接•扩展工业温度范围：-40°C至+125°C
2应用
•通道隔离的可编程逻辑控制器(PLC)模拟输入模块•测试和测量•电池组监视
3说明
ADS8681、ADS8685和ADS8689器件属于集成数据采集系统系列，均基于逐次逼近(SAR)模数转换器(ADC)。
此类器件采用高速高精度SARADC、集成模拟前端(AFE)输入驱动器电路、高达±20V的过压保护电路以及一个温度漂移极低的4.096V片上基准。
此类器件由5V模拟单电源供电，但支持±12.288V、±6.144V、±10.24V、±5.12V和±2.56V实际双极输入范围以及0V至12.288V、0V至10.24V、0V至6.144V和0V至5.12V单极输入范围。
各输入范围的增益和偏移误差均可在特定数值范围内进行调节，确保直流精度较高。
通过针对器件内部寄存器进行编程可选择输入范围。
该器件提供恒定阻性输入阻抗(≥1MΩ)，不受所选输入范围的影响。
multiSPI数字接口向后兼容传统SPI协议。
此外，该器件的可配置特性便于连接各种主机控制器。
器件型号ADS868x 器件信息
(1) 封装TSSOP(16)WQFN(16) 封装尺寸（标称值）5.00mmx4.40mm4.00mmx4.00mm
(1)要了解所有可用封装，请见数据表末尾的可订购产品附录。
AVDD DVDD方框图 ADS868x 4.096-VReference REFIOREFCAP AIN_PAIN_GND 1M:1M: OVPOVP PGA 2nd-OrderLPF ADCDriver VBIAS Oscillator 16-BitSARADC DigitalLogicandInterface CONVST/CSSCLKSDISDO AGND DGND REFGNDCopyright©2016,TexasInstrumentsIncorporated
1 AnIMPORTANTNOTICEattheendofthisdatasheetaddressesavailability,warranty,changes,useinsafety-criticalapplications, intellectualpropertymattersandotherimportantdisclaimers.PRODUCTIONDATA. EnglishDataSheet:SBAS633 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 目录 1特性..........................................................................12应用..........................................................................13说明..........................................................................14修订历史记录...........................................................25PinConfigurationandFunctions.........................46Specifications.........................................................5 6.1AbsoluteMaximumRatings......................................56.2ESDRatings..............................................................56.3mendedOperatingConditions.......................56.4ThermalInformation..................................................56.5ElectricalCharacteristics...........................................66.6TimingRequirements:ConversionCycle................106.7TimingRequirements:AsynchronousReset...........106.8TimingRequirements:SPI-CompatibleSerial Interface...................................................................106.9TimingRequirements:Source-SynchronousSerial Interface(ExternalClock)........................................116.10TimingRequirements:Source-SynchronousSerial Interface(InternalClock)..........................................116.11TypicalCharacteristics..........................................157DetailedDescription............................................227.1Overview.................................................................227.2FunctionalBlockDiagram.......................................22 7.3FeatureDescription.................................................237.4DeviceFunctionalModes........................................357.5Programming...........................................................407.6RegisterMaps.........................................................488ApplicationandImplementation........................568.1ApplicationInformation............................................568.2TypicalApplication.................................................569PowerSupplymendations......................609.1PowerSupplyDecoupling.......................................609.2PowerSaving..........................................................6010Layout...................................................................6110.1LayoutGuidelines.................................................6110.2LayoutExample....................................................6211器件和文档支持.....................................................6311.1文档支持................................................................6311.2相关链接................................................................6311.3接收文档更新通知.................................................6311.4社区资源................................................................6311.5商标.......................................................................6311.6静电放电警告.........................................................6311.7Glossary................................................................6312机械、封装和可订购信息.......................................64 4修订历史记录 注：之前版本的页码可能与当前版本有所不同。
ChangesfromRevisionA(March2016)toRevisionB Page •已添加ADS8685和ADS8689器件至文档
2 版权©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 ChangesfromOriginal(February2016)toRevisionA Page •已发布为量产数据
1 Copyright©2016,TexasInstrumentsIncorporated
3 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 5PinConfigurationandFunctions PWPackage16-PinTSSOPTopView(NottoScale) DGND1AVDD2AGND3REFIO4REFGND5REFCAP6AIN_P7AIN_GND8 16DVDD15RVS14ALARM/SDO-1/GPO13SDO-012SCLK11CONVST/CS10SDI9RST AGNDREFIOREFGNDREFCAP AVDDDGNDDVDDRVS RUMPackage16-PinWQFNTopView(NottoScale) ALARM/SDO-1/GPOSDO-0SCLKCONVST/CS AIN_PAIN_GND RSTSDI NAMEAGNDAIN_GNDAIN_PALARM/SDO-1/GPOAVDD CONVST/CS DGNDDVDDREFCAPREFGNDREFIORSTRVS SCLKSDISDO-
0 NO. TSSOP WQFN
3 1
8 6
7 5 14 12
2 16 11
9 1 15 16 14
6 4
5 3
4 2
9 7 15 13 12 10 10
8 13 11 TYPE
(1) PinFunctions DESCRIPTION
P Analoggroundpin.DecouplewiththeAVDDpin. AI Analoginput:negative.DecouplewiththeAIN_Ppin. AI Analoginput:positive.DecouplewiththeAIN_GNDpin. DO Multi-functionoutputpin.Activehighalarm. Dataoutput1formunication.General-purposeoutputpin.
P Analogsupplypin.DecouplewiththeAGNDpin. Dual-functionalitypin. Activehighlogic:conversionstartinputpin;aCONVSTrisingedgebringsthedevicefrom DI acquisitionphasetoconversionphase. Activelowlogic:chip-selectinputpin;thedevicetakescontrolofthedatabuswhenCSislow; theSDO-xpinsgototri-statewhenCSishigh.
P Digitalgroundpin.DecouplewiththeDVDDpin.
P Digitalsupplypin.DecouplewiththeDGNDpin. AO ADCreferencebufferdecouplingcapacitorpin.DecouplewiththeREFGNDpin.
P Referencegroundpin;shorttotheanaloggroundplane.DecouplewiththeREFIOand REFCAPpins. AIOInternalreferenceoutputandexternalreferenceinputpin.DecouplewithREFGND. DI Activelowlogicinputtoresetthedevice. Multi-functionoutputpinforserialinterface;seetheRESETStatesection. DO WithCSheldhigh,RVSreflectsthestatusoftheinternalADCSTsignal. WithCSlow,thestatusofRVSdependsontheoutputprotocolselection. DI munication:clockinputpinfortheserialinterface. Allsystem-synchronousdatatransferprotocolsaretimedwithrespecttotheSCLKsignal. DI Dualfunction:datainputpinformunication. Chaindatainputduringmunicationindaisy-chainmode. DO munication:dataoutput0
(1)AI=analoginput,AIO=analoginput/output,DI=digitalinput,DO=digitaloutput,andP=powersupply.
4 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 6Specifications 6.1AbsoluteMaximumRatings overoperatingfree-airtemperaturerange(unlessotherwisenoted)
(1) AIN_
P,AIN_GNDtoGND AVDD=5V
(2)AVDD=floating
(3) AVDDtoGNDorDVDDtoGND REFCAPtoREFGNDorREFIOtoREFGND GNDtoREFGND DigitalinputpinstoGND DigitaloutputpinstoGND Temperature Operating,TAStorage,Tstg MIN MAX UNIT –20 20
V –11 11 –0.3
7 V –0.3 5.7
V –0.3 0.3
V –0.3 DVDD
+0.3
V –0.3 DVDD+0.3
V –40 125 °
C –65 150
(1)StressesbeyondthoselistedunderAbsoluteMaximumRatingsmaycausepermanentdamagetothedevice.Thesearestressratingsonly,anddonotimplyfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedundermendedOperatingConditions.Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability.
(2)AVDD=5Voffersalowimpedanceof<30kΩ.
(3)AVDD=floatingwithanimpedance>30kΩ. 6.2ESDRatings V(ESD) Electrostaticdischarge AnaloginputpinsHumanbodymodel(HBM),perANSI/ESDA/JEDECJS-001
(1)(AIN_
P,AIN_GND) Allotherpins Chargeddevicemodel(CDM),perJEDECspecificationJESD22-C101
(2)
(1)JEDECdocumentJEP155statesthat500-VHBMallowssafemanufacturingwithastandardESDcontrolprocess.
(2)JEDECdocumentJEP157statesthat250-VCDMallowssafemanufacturingwithastandardESDcontrolprocess. VALUE±4000±2000±500 UNITV 6.3mendedOperatingConditions overoperatingfree-airtemperaturerange(unlessotherwisenoted) MIN AVDD Analogsupplyvoltage 4.75 DVDD Digitalsupplyvoltage 1.65 NOM5 3.3 MAX5.25AVDD UNITVV 6.4ThermalInformation THERMALMETRIC
(1) RθJARθ)RθJBψJTψJBRθJC(bot) Junction-to-ambientthermalresistanceJunction-to-case)thermalresistanceJunction-to-boardthermalresistancecharacterizationparameterJunction-to-boardcharacterizationparameterJunction-to-case(bottom)thermalresistance ADS8681,ADS8685,ADS8689 PW(TSSOP)RUM(WQFN) 16PINS 16PINS 95.7 31.9 29.3 27.9 41.5 7.4 1.5 0.3 40.8 7.4 N/A 1.9 UNIT °C/W°C/W°C/W°C/W°C/W°C/W
(1)Formoreinformationabouttraditionalandnewthermalmetrics,seetheSemiconductorandICPackageThermalMetricsapplicationreport. Copyright©2016,TexasInstrumentsIncorporated
5 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 6.5ElectricalCharacteristics allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) PARAMETER TESTCONDITIONS MIN TYP MAXUNIT ANALOGINPUTS Inputrange=±3×VREF –12.288 12.288 Inputrange=±2.5×VREF –10.24 10.24 Inputrange=±1.5×VREF –6.144 6.144 Full-scaleinputspan
(1) VIN (AIN_PtoAIN_GND) Inputrange=±1.25×VREFInputrange=±0.625×VREFInputrange=3×VREF –5.12–2.56
0 5.12 2.56
V 12.288 Inputrange=2.5×VREF
0 10.24 Inputrange=1.5×VREF
0 6.144 Inputrange=1.25×VREF
0 5.12 Inputrange=±3×VREF –12.288 12.288 Inputrange=±2.5×VREF –10.24 10.24 Inputrange=±1.5×VREF –6.144 6.144 Inputrange=±1.25×VREF –5.12 5.12 AIN_
P Operatinginputrange Inputrange=±0.625×VREF –2.56 2.56
V Inputrange=3×VREF
0 12.288 Inputrange=2.5×VREF
0 10.24 Inputrange=1.5×VREF
0 6.144 Inputrange=1.25×VREF
0 5.12 AIN_GND Operatinginputrange Allinputranges –0.1
0 0.1
V Inputrange=±3×VREF 1.02 1.2 1.38 Inputrange=±1.5×VREF 1.02 1.2 1.38 Inputrange=3×VREF 1.02 1.2 1.38 Inputrange=1.5×VREF 1.02 1.2 1.38 RIN Inputimpedance AtTA=25°CInputrange=±2.5×VREF 0.85
1 1.15MΩ Inputrange=±1.25×VREF 0.85
1 1.15 Inputrange=±0.625×VREF 0.85
1 1.15 Inputrange=2.5×VREF 0.85
1 1.15 Inputrange=1.25×VREF 0.85
1 1.15 Inputimpedancedrift
7 25ppm/°
C Inputrange=±3×VREF (VIN–2.5)/RIN Inputrange=±2.5×VREF (VIN–2.2)/RIN Inputrange=±1.5×VREF (VIN–2.0)/RIN IIN Inputcurrent WithvoltageattheAIN_Ppin=VIN Inputrange=±1.25×VREFInputrange=±0.625×VREFInputrange=3×VREF (VIN–2.0)/RIN (VIN–1.6)/RIN µ
A (VIN–2.6)/RIN Inputrange=2.5×VREF (VIN–2.5)/RIN Inputrange=1.5×VREF (VIN–2.7)/RIN Inputrange=1.25×VREF (VIN–2.5)/RIN INPUTOVERVOLTAGEPROTECTIONCIRCUIT VOVP Allinputranges AVDD=5Vorofferslowimpedance<30kΩ, –20 allinputranges AVDD=floatingwithimpedance>30kΩ, –11 allinputranges 20V 11 INPUTBANDWIDTH f–3dBf–0.1dB Small-signalInputbandwidth –3dB–0.1dB AllinputrangesAllinputranges 15kHz 2.5
(1)Idealinputspan,doesnotincludegainoroffseterror.
6 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 ElectricalCharacteristics(continued) allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) PARAMETER TESTCONDITIONS MIN TYP MAXUNIT SYSTEMPERFORMANCE Resolution 16 Bits NMC Nomissingcodes 16 Bits DNL Differentialnonlinearity
(2) Allinputranges –0.7 ±0.4 0.7LSB Allbipolarranges
(3) –1.2 ±0.5 1.2 INL Integralnonlinearity
(2) Allunipolarranges
(4) ADS8681ADS8685,ADS8689 –1.5 ±0.5 –1.2 ±0.5 1.5LSB1.2 EO Offseterror
(5) AtTA=25°
C Allbipolarranges
(3)Allunipolarranges
(4) –
1 ±0.2 –
2 ±0.2 1mV
2 Offseterrordriftwithtemperature Allinputranges –
3 ±0.75 3ppm/°
C EG Gainerror
(6) AtTA=25°C,allinputranges Gainerrordriftwithtemperature
(7) Allinputranges –0.025–
5 ±0.01±
1 0.0255 %FSRppm/°
C DYNAMICCHARACTERISTICS Inputrange=±3×VREF ADS8681ADS8685,ADS8689 90.25 92 90.5 92 Inputrange=±2.5×VREF ADS8681ADS8685,ADS8689 90.25 92 90.5 92 SNR Signal-to-noiseratio
(8) Inputrange=±1.5×VREFInputrange=±1.25×VREF 89.5 91.5 89.5 91.5 dB Inputrange=±0.625×VREF 87.75 90 Inputrange=3×VREF 89.25 91 Inputrange=2.5×VREF 89 91 Inputrange=1.5×VREF 88 90 Inputrange=1.25×VREF 87.5 90 THD Totalharmonicdistortion
(9)(8) Allinputranges ADS8681ADS8685,ADS8689 –107dB –112 Inputrange=±3×VREF ADS8681ADS8685,ADS8689 90.15 92 90.4 92 Inputrange=±2.5×VREF ADS8681ADS8685,ADS8689 90.15 92 90.4 92 SINAD Signal-to-noise+distortion
(8) Inputrange=±1.5×VREFInputrange=±1.25×VREF 89.4 91.5 89.4 91.5 dB Inputrange=±0.625×VREF 87.65 90 Inputrange=3×VREF 89 91 Inputrange=2.5×VREF 88.75 91 Inputrange=1.5×VREF 87.75 90 Inputrange=1.25×VREF 87.25 90 SFDR Spurious-freedynamicrange
(8) Allinputranges ADS8681ADS8685,ADS8689 109dB 114
(2)ThisspecificationindicatestheendpointINL,notbest-fitINL.
(3)Bipolarrangesare±12.288V,±10.24V,±6.144V,±5.12V,and±2.56V.
(4)Unipolarrangesare0V–12.288V,0V–10.24V,0V–6.144V,and0V–5.12V.
(5)Measuredrelativetoactualmeasuredreference.
(6)Excludesinternalreferenceuracyerror.
(7)Excludesinternalreferencetemperaturedrift.
(8)Allspecificationsexpressedindecibels(dB)refertothefull-scaleinput(FSR)andaretestedwitha1-kHzinputsignal0.25dBbelow full-scale,unlessotherwisespecified.
(9)Calculatedonthefirstnineharmonicsoftheinputfrequency. Copyright©2016,TexasInstrumentsIncorporated
7 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 ElectricalCharacteristics(continued) allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) PARAMETER TESTCONDITIONS MIN TYP MAXUNIT SAMPLINGDYNAMICS ADS8681 665 tCONV Conversiontime ADS8685 1000ns ADS8689 5000 ADS8681 335 tACQ Acquisitiontime ADS8685 1000 ns ADS8689 5000 fcycleMwiathxoimutulmatethnrcoyughputrate ADS8681ADS8685ADS8689 1000500100 kSPS INTERNALREFERENCEOUTPUT VREFIO OntheREFIOpin(configuredasanoutput) AtTA=25°
C TSSOP(PW)WQFN(RUM) 4.095 4.096 4.097
V 4.094 4.096 4.098 dVREFIO/dTA Internalreferencetemperaturedrift TSSOP(PW)WQFN(RUM)
4 7 ppm/°
C 5 COUT_REFIO DecouplingcapacitoronREFIOpin 4.7 µ
F VREFCAP ReferencevoltagetotheADC(ontheREFCAPpin) AtTA=25°
C 4.095 4.096 4.097
V REFCAPtemperaturedrift 0.5 2ppm/°
C COUT_REFCAP DecouplingcapacitoronREFCAPpin 10 μ
F Turn-ontime COUT_REFCAP=10µ
F,COUT_REFIO=10µ
F 20 ms EXTERNALREFERENCEINPUT VREFIO_EXT ExternalreferencevoltageonREFIOREFIOpinconfiguredasaninput 4.046 4.096 4.146
V AVDDCOMPARATOR VTH_HIGH Highthresholdvoltage 5.3
V VTH_LOW Lowthresholdvoltage 4.7
V POWER-SUPPLYREQUIREMENTS AVDD Analogpower-supplyvoltage 4.75
5 5.25 DVDD Digitalpower-supplyvoltage OperatingrangeSupplyrangeforspecifiedperformance 1.65 3.3AVDD
V 2.7 3.3AVDD IAVDD_DYN Analogsupplycurrent,deviceconvertingatmaximumthroughput Internalreference Externalreference ADS8681ADS8685ADS8689ADS8681ADS8685ADS8689 8.2 10.5 5.6 7.25
4 5 mA 7.0 8.75 4.4 5.5 2.7 3.25 IAVDD_STC Analogsupplycurrent,devicenotconverting Internalreference Externalreference ADS8681ADS8685,ADS8689ADS8681ADS8685,ADS8689 4.7 6.25 3.5 4.7 mA 3.5 4.5 2.3
3 IAVDD_STDBY Analogsupplycurrent,deviceinSTANDBYmode InternalreferenceExternalreference 2.8mA 1.6 IAVDD_PD Analogsupplycurrent,deviceinPDmode InternalreferenceExternalreference 10μA 10 IDVDD_DYN Digitalsupplycurrent,maximumthroughput 0.2 0.25mA IDVDD_STDBY Digitalsupplycurrent,deviceinSTANDBYmode
1 μ
A IDVDD_PD Digitalsupplycurrent,deviceinPDmode
1 μ
A 8 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 ElectricalCharacteristics(continued) allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) PARAMETER TESTCONDITIONS MIN TYP MAXUNIT DIGITALINPUTS(CMOS) DVDD>2.35V VIH Digitalhighinputvoltagelogiclevel DVDD≤2.35V 0.7×DVDD 0.8×DVDD DVDD+0.3V DVDD+0.3 DVDD>2.35V VIL Digitallowinputvoltagelogiclevel DVDD≤2.35V –0.3 0.3× DVDD
V –0.3 0.2× DVDD Inputleakagecurrent 100 nA Inputpincapacitance
5 pF DIGITALOUTPUTS(CMOS) VOH DigitalhighoutputvoltagelogiclevelIO=500-μAsource 0.8×DVDD DVDD
V VOL Digitallowoutputvoltagelogiclevel IO=500-μAsink
0 0.2×
V DVDD Floatingstateleakagecurrent Onlyfordigitaloutputpins
1 µ
A Internalpincapacitance
5 pF TEMPERATURERANGE TA Operatingfree-airtemperature –40 125°
C Copyright©2016,TexasInstrumentsIncorporated
9 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 6.6TimingRequirements:ConversionCycle allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) MIN TYP MAXUNIT TIMINGREQUIREMENTS ADS8681 1000 fcycle Samplingfrequency ADS8685 500kSPS ADS8689 100 tcycle ADCcycletimeperiod 1/fcycle ADS8681 335 tacq Acquisitiontime ADS8685 1000 ns ADS8689 5000 TIMINGSPECIFICATIONS ADS8681 665 tconv Conversiontime ADS8685 1000ns ADS8689 5000 6.7TimingRequirements:AsynchronousReset allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) MIN TYP MAXUNIT TIMINGREQUIREMENTS twl_RST Pulseduration:RSThigh 100 ns TIMINGSPECIFICATIONS tD_RST_PORDelaytimeforPORreset:RSTrisingtoRVSrising 20 ms tD_RST_APPDelaytimeforapplicationreset:RSTrisingtoCONVST/CSrising
1 µs tNAP_WKUPWake-uptime:NAPmode 20 µs tPWRUP Power-uptime:PDmode 20 ms 6.8TimingRequirements:SPI-CompatibleSerialInterface allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) MIN TYP MAXUNIT TIMINGREQUIREMENTS fCLK Serialclockfrequency 66.67MHz tCLK Serialclocktimeperiod 1/fCLK tPH_CK SCLKhightime 0.45 0.55 tCLK tPL_CK SCLKlowtime 0.45 0.55 tCLK tSU_CSCK Setuptime:CONVST/CSfallingtofirstSCLKcaptureedge 7.5 ns tSU_CKDI Setuptime:SDIdatavalidtoSCLKcaptureedge 7.5 ns tHT_CKDI Holdtime:SCLKcaptureedgeto(previous)datavalidonSDI 7.5 ns tHT_CKCS Delaytime:lastSCLKcaptureedgetoCONVST/CSrising 7.5 ns TIMINGSPECIFICATIONS tDEN_CSDODelaytime:CONVST/CSfallingedgetodataenable 9.5 ns tDZ_CSDO Delaytime:CONVST/CSrisingtoSDO-xgoingto3-state 10 ns tD_CKDO Delaytime:SCLKlaunchedgeto(next)datavalidonSDO-x 12 ns tD_CSRVS Delaytime:CONVST/CSrisingedgetoRVSfalling 14 ns 10 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 6.9TimingRequirements:Source-SynchronousSerialInterface(ExternalClock) allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) MIN TYP MAXUNIT TIMINGREQUIREMENTS fCLK Serialclockfrequency 66.67MHz tCLK Serialclocktimeperiod 1/fCLK tPH_CK SCLKhightime 0.45 0.55tCLK tPL_CK SCLKlowtime 0.45 0.55tCLK TIMINGSPECIFICATIONS tDEN_CSDODelaytime:CONVST/CSfallingedgetodataenable 9.5ns tDZ_CSDODelaytime:CONVST/CSrisingtoSDO-xgoingto3-state 10ns tD_CKRVS_rDelaytime:SCLKrisingedgetoRVSrising 14ns tD_CKRVS_fDelaytime:SCLKfallingedgetoRVSfalling 14ns tD_RVSDODelaytime:RVSrisingto(next)datavalidonSDO-x 2.5ns tD_CSRVSDelaytime:CONVST/CSrisingedgetoRVSdisplayinginternaldevicestate 15ns 6.10TimingRequirements:Source-SynchronousSerialInterface(InternalClock) allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) MIN TYP MAXUNIT TIMINGSPECIFICATIONS tDEN_CSDODelaytime:CONVST/CSfallingedgetodataenable 9.5 ns tDZ_CSDO Delaytime:CONVST/CSrisingtoSDO-xgoingto3-state 10 ns tDEN_CSRVSDelaytime:CONVST/CSfallingedgetofirstrisingedgeonRVS 50 ns tD_RVSDODelaytime:RVSrisingto(next)datavalidonSDO-x 2.5 ns tINTCLK Timeperiod:internalclock 15 ns tCYC_RVS Timeperiod:RVSsignal 15 ns tWH_RVS RVShightime 0.4 0.6tINTCLK tWL_RVS RVSlowtime 0.4 0.6tINTCLK tD_CSRVS Delaytime:CONVST/CSrisingedgetoRVSdisplayinginternaldevicestate 15 ns Copyright©2016,TexasInstrumentsIncorporated 11 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 CONVST/CSADCST(Internal) tcycletconv TheCSfallingedgecanbeissuedaftertconv_maxorwhenRVSgoeshigh. tacq RVS Figure1.ConversionCycleTimingDiagram RSTRVS trsttwl_RST td_rst Figure2.AsynchronousResetTimingDiagram CONVST/CSRVS tconv_maxtD_CSRVS SCLK CPOL=0CPOL=
1 tcycle DataReadTime tD_CSRVStSU_CSCK tHT_CKCS SDO-0SDI tDEN_CSDO tD_CKDO tD_CSDO
M M-
1 M-
2 L+
1 L tSU_CKDI tHT_CKDI Figure3.StandardSPIInterfaceTimingDiagramforCPHA=
0 12 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 tconv_max tcycleDataReadTime CONVST/CS RVS tD_CSRVS SCLK CPOL=0CPOL=
1 tD_CSRVStSU_CSCK tHT_CKCS SDO-0SDI tDEN_CSDO 0MtSU_CKDI tD_CKDO M-
1 L+1L tHT_CKDI tDZ_CSDO Figure4.StandardSPIInterfaceTimingDiagramforCPHA=
1 CONVST/CSRVS tconv_maxtD_CSRVS SCLK CPOL=0CPOL=
1 tcycle DataReadTime tD_CSRVStSU_CSCK tHT_CKCS SDO-
0 tDEN_CSDO tD_CKDO tD_CSDO
M M-
2 M-
4 L+
3 L+
1 SDO-1SDI M-
1 M-
3 M-
5 L+
2 L tSU_CKDI tHT_CKDI Figure5.multiSPIInterfaceTimingDiagramforDualSDO-xandCPHA=
0 Copyright©2016,TexasInstrumentsIncorporated 13 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 CONVST/CSRVS tconv_maxtD_CSRVS SCLK CPOL=0CPOL=
1 SDO-
0 tDEN_CSDO tcycleDataReadTime tD_CSRVStSU_CSCK tHT_CKCS tD_CKDO tDZ_CSDO
0 M M-
2 L+3L+
1 SDO-
1 0 M-
1 M-
1 L+
2 L tSU_CKDI tHT_CKDI SDI Figure6.multiSPIInterfaceTimingDiagramforDualSDO-xandCPHA=
1 CONVST/CSSCLKSDO-0RVS tconvtD_CSRD DataReadTime tSU_CSCK tDEN_CSDO M tD_CKRVS_f tD_RVSDO M-
1 M-kM-k-1M-k-
2 L+
1 tD_CKRVS_r L tD_CSRVS tDZ_CSDO Figure7.multiSPISource-SynchronousExternalClockSerialInterfaceTimingDiagram CONVST/CS tconv_max DataReadTime SCLK tDEN_CSDO SDO-
0 M M-
1 M-kM-k-1M-k-
2 L+
1 L tDEN_CSRVS tD_RVSDO tWH_RVS tD_CSRVS RVS tCYC_RVS tWL_RVS Figure8.multiSPISource-SynchronousInternalClockSerialInterfaceTimingDiagram tDZ_CSDO 14 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 6.11TypicalCharacteristics atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 15 ±12.288V ±10.24V
9 ±6.144V ±5.12V ±2.56V 0-12.288V
3 0-10.24V 0-6.144V 0-5.12V -
3 15 -40C 25C
9 125C
3 -
3 AnalogInputCurrent(uA) AnalogInputCurrent(uA) -
9 -
9 InputImpedanceDrift(ppm) -15-12.288-8.192 -4.096
0 4.096 InputVoltage(V) 8.192 12.288 D001 Figure9.InputI-VCharacteristicAcrossInputRanges 400 200
0 -200 -400-40 ±12.288V±10.24V±6.144V±5.12V±2.56V 0-12.288V0-10.24V0-6.144V0-5.12V -
7 26 59 92 Free-AirTemperature(qC) 125 D003 Figure11.InputImpedanceDriftvsTemperature 45000 40000 35000 30000 25000 20000 15000 10000 5000
0 327663276732768327693277032771 OutputCodes D007 Mean=32768.24,sigma=0.57,input=0V Figure13.DCHistogramforMid-ScaleInputs(±12.288V) NumberofHits NumberofDevices -15-12.288-8.192 -4.096
0 4.096 InputVoltage(V) Range=±12.288V 8.192 12.288 D002 Figure10.InputI-VCharacteristicAcrossTemperature 1600 1400 1200 1000 800 600 400 200 01.021.061.11.141.181.221.261.3InputImpedance(M:) Numberofsamples=3398 1.341.38 D004 Figure12.TypicalDistributionofInputImpedance 45000 40000 35000 30000 25000 20000 15000 10000 5000
0 327663276732768327693277032771 OutputCodes D0083 Mean=32767.24,sigma=0.56,input=0V Figure14.DCHistogramforMid-ScaleInputs(±10.24V) NumberofHits Copyright©2016,TexasInstrumentsIncorporated 15 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 40000 45000 NumberofHits 300002000010000 NumberofHits 3000015000 NumberofHits
0 32766327673276832769327703277132772 OutputCodes D009 Mean=32768.21,sigma=0.62,input=0V Figure15.DCHistogramforMid-ScaleInputs(±6.144V) 36000 30000 24000 18000 12000 6000
0 3276532766327673276832769327703277132772 OutputCodes D011 Mean=32768.22,sigma=0.75,input=0V 40000 Figure17.DCHistogramforMid-ScaleInputs(±2.56V) NumberofHits
0 32766327673276832769327703277132772 OutputCodes D010 Mean=32768.11,sigma=0.62,input=0V Figure16.DCHistogramforMid-ScaleInputs(±5.12V) 50000 40000 30000 20000 10000
0 32765327663276732768327693277032771 OutputCodes D012 Mean=32767.73,sigma=0.60,input=6.144V 40000 Figure18.DCHistogramforMid-ScaleInputs(0V–12.288V) 30000 30000 NumberofHits NumberofHits 20000 20000 10000 10000
0 32766327673276832769327703277132772 OutputCodes D013 Mean=32768.41,sigma=0.62,input=5.12V Figure19.DCHistogramforMid-ScaleInputs(0V–10.24V)
0 32766327673276832769327703277132772 OutputCodes D014 Mean=32768.42,sigma=0.76,input=3.072V Figure20.DCHistogramforMid-ScaleInputs(0V–6.144V) 16 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 40000 0.7 DifferentialNonlinearity(LSB) 0.530000 0.3 NumberofHits 0.120000 -0.1 10000-0.3-0.5 DifferentialNonlinearity(LSB)
0 32766327673276832769327703277132772 OutputCodes D015 Mean=32768.32,sigma=0.78,input=2.56V Figure21.DCHistogramforMid-ScaleInputs(0V–5.12V) 0.7 Maximum 0.5 Minimum 0.3 0.1 -0.1 -0.3 -0.5 IntegralNonlinearity(LSB) -0.70 1.20.80.4 0-0.4-0.8 16384 32768Codes(LSB) Allinputranges 49152 Figure22.TypicalDNLforAllCodes 65535 D016 -0.7-40 1.51 0.5 -
7 26 59 92 Free-AirTemperature(0C) Allinputranges Figure23.DNLvsTemperature 125 D017 -1.20 16384 32768Codes(LSB) 49152 65535 D018 Figure24.TypicalINLforAllCodes(AllBipolarRanges) 1.2MaximumMinimum 0.6 IntegralNonlinearity(LSB) IntegralNonlinearity(LSB)
0 0 -0.5-0.6 -
1 -1.50 16384 32768Codes(LSB) 49152 65536 D023 -1.2-40 -
7 26 59 92 Free-AirTemperature(0C) 125 D027 Figure25.TypicalINLforAllCodes(AllUnipolarRanges) Figure26.INLvsTemperature(AllBipolarRanges) Copyright©2016,TexasInstrumentsIncorporated 17 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 1.5
1 Maximum ±12.288V ±5.12V 0-10.24V Minimum 0.75 ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V 0.75 0.5 OffsetError(mV) IntegralNonlinearity(LSB) 0.25
0 0 -0.25 -0.75 -0.5 -0.75 -1.5-40 -
7 26 59 92 Free-AirTemperature(0C) 125 D032 -1-40 -
7 26 59 92 Free-AirTemperature(0C) 125 D036 Figure27.INLvsTemperature(AllUnipolarRanges) 12.510 0.0250.015 Figure28.OffsetErrorvsTemperatureAcrossInputRanges ±12.288V±10.24V±6.144V ±5.12V±2.56V0-12.288V 0-10.24V0-6.144V0-5.12V GainError(%FSR) NumberofDevices 7.5 0.005
5 -0.005 2.5 -0.015
0 00.20.40.60.811.21.41.61.82.02.22.42.62.83 OffsetDrift(ppm/ºC) D037 -0.025-40 -
7 26 59 92 Free-AirTemperature(0C) 125 D038 NumberofUnits Figure29.TypicalHistogramforOffsetDrift 25 20 15 10
5 0 00.511.522.533.544.55 GainDrift(ppm/ºC) D039 GainError(%FSR) Figure30.GainErrorvsTemperatureAcrossInputRanges 1.11 0.90.80.70.60.50.40.30.20.1 0-0.1
0 ±12.288V±10.24V±6.144V±5.12V±2.56V0-12.288V0-10.24V0-6.144V0-5.12V 2000 4000 6000 SourceResistance(:) 8000 10000 D040 Figure31.TypicalHistogramforGainErrorDrift Figure32.GainErrorvsExternalResistance(REXT) 18 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted)
0 0 -40 -40 Amplitude(dB) Amplitude(dB) -80 -80 -120 -120 -160 -160 -2000 100000 200000300000InputFrequency(Hz) 400000 Numberofpoints=64k,fIN=1kHz 500000 D041 Figure33.TypicalFFTPlot(AllRanges)fortheADS8681
0 -40 -80 -120 -160 Signal-to-NoiseRatio(dB) -2000 50000 100000150000InputFrequency(Hz) 200000 Numberofpoints=64k,fIN=1kHz 250000 D001 Figure34.TypicalFFTPlot(AllRanges)fortheADS8685 94.5 ±12.288V ±5.12V 0-10.24V ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V 93 91.5 90 Amplitude(dB) Signal-to-NoiseRatio(dB) -2000 20000 40000 60000 InputFrequency(Hz) 80000 Numberofpoints=64k,fIN=1kHz 100000 D002 Figure35.TypicalFFTPlot(AllRanges)fortheADS8689 96 ±12.288V ±5.12V 0-10.24V 95 ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V 94 93 92 91 90 89 88-40 -
7 26 59 92 Free-AirTemperature(0C) fIN=1kHz 125 D051 Figure37.SNRvsTemperature Signal-to-Noise+DistortionRatio(dB) 88.5100 1000InputFrequency(Hz) 10000 D050 94939291908988 100 Figure36.SNRvsInputFrequency ±12.288V±10.24V±6.144V ±5.12V±2.56V0-12.288V 0-10.24V0-6.144V0-5.12V 1000InputFrequency(Hz) 10000 D052 Figure38.SINADvsInputFrequency Copyright©2016,TexasInstrumentsIncorporated 19 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) TotalHarmonicDistortionRatio(dB) Signal-to-Noise+DistortionRatio(dB) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 96 ±12.288V ±5.12V 0-10.24V 95 ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V -80 ±12.288V ±5.12V 0-10.24V ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V 94 -90 93 92 -100 91 90 -110 89 88-40 -
7 26 59 92 Free-AirTemperature(0C) fIN=1kHz 125 D053 -120100 1000InputFrequency(Hz) 10000 D054 Figure39.SINADvsTemperature -80 ±12.288V ±5.12V 0-10.24V ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V -90 Figure40.THDvsInputFrequency 987 IAVDDDynamic(mA) TotalHarmonicDistortion(dB)
6 -100
5 4 -110 -120-40 -
7 26 59 92 Free-AirTemperature(0C) fIN=1kHz 125 D055
3 ADS8681
2 ADS8685 ADS8689
1 -40 -
7 26 59 92 125 Free-AirTemperature(qC) D003 Figure41.THDvsTemperature
9 Figure42.AVDDCurrentvsTemperature
5 8 4.57 IAVDDStatic(mA) IAVDDCurrent(mA)
6 4
5 4 3.5
3 2 ADS8681 ADS8685
1 0 200 400 600 800 1000 Throughput(ksps) D005 3 2.5-40 ADS8681ADS8685ADS8689 -
7 26 59 92 Free-AirTemperature(qC) 125 D004 Figure43.AVDDCurrentvsThroughput Figure44.AVDDCurrentvsTemperature(DuringSampling) 20 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 2.8 ±12.288V ±5.12V 0-10.24V ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V 2.7
3 ±12.288V ±5.12V 0-10.24V ±10.24V ±2.56V 0-6.144V 2.5 ±6.144V 0-12.288V 0-5.12V
2 IAVDDStandby(mA)IAVDDPD(uA) 2.6 1.5 12.5 0.5 2.4-40 -
7 26 59 92 Free-AirTemperature(0C) 125 D067
0 -40 -
7 26 59 92 125 Free-AirTemperature(0C)D068 Figure45.AVDDCurrentvsTemperature(StandbyMode) Figure46.AVDDCurrentvsTemperature(Power-DownMode) Copyright©2016,TexasInstrumentsIncorporated 21 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 7DetailedDescription 7.1Overview TheADS868xdevicesbelongtoafamilyofhigh-speed,high-performance,easy-to-useintegrateddataacquisitionsystem.Thissingle-channeldevicesupportstruebipolarinputvoltageswingsupto±12.288V,operatingonasingle5-Vanalogsupply.ThedevicefeaturesanenhancedSPIinterface(multiSPI)thatallowsthesamplingratetobemaximizedevenwithlowerspeedhostcontrollers. Thedeviceconsistsofahigh-precisionessiveapproximationregister(SAR)analog-to-digitalconverter(ADC)andapower-optimizedanalogfront-end(AFE)circuitforsignalconditioningthatincludes:•Ahigh-resistiveinputimpedance(≥1MΩ)thatisindependentofthesamplingrate•Aprogrammablegainamplifier(PGA)withapseudo-differentialinputconfigurationsupportingninesoftware- programmableunipolarandbipolarinputranges•Asecond-order,low-passantialiasingfilter•AnADCdriveramplifierthatensuresquicksettlingoftheSARADCinputforhighuracy•Aninputovervoltageprotectioncircuitupto±20V Thedevicealsofeaturesalowtemperaturedrift,4.096-Vinternalreferencewithafast-settlingbufferandamultiSPIserialinterfacewithdaisy-chain(DAISY)andALARMfeatures. TheintegrationofthemultichannelprecisionAFEcircuitwithhighinputimpedanceandaprecisionADCoperatingfromasingle5-Vsupplyoffersasimplifiedendsolutionwithoutrequiringexternalhigh-voltagebipolarsuppliesplicateddrivercircuits. 7.2FunctionalBlockDiagram AVDDADS868x DVDD 4.096-VReference REFIOREFCAP AIN_PAIN_GND 1M:1M: OVPOVP PGA AGND 2nd-OrderLPF ADCDriver VBIAS Oscillator 16-BitSARADC DigitalLogicandInterface CONVST/CSSCLKSDISDO DGND REFGNDCopyright©2016,TexasInstrumentsIncorporated 22 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 7.3FeatureDescription 7.3.1AnalogInputStructure Thedevicefeaturesapseudo-differentialinputstructure,meaningthatthesingle-endedanaloginputsignalisappliedatthepositiveinputAIN_PandthenegativeinputAIN_GNDistiedtoGND.Figure47showsthesimplifiedcircuitschematicfortheAFEcircuit,includingtheinputovervoltageprotectioncircuit,PGA,low-passfilter(LPF),andhigh-speedADCdriver. AIN_PAIN_GND 1M:OVP OVP1M: PGA 2nd-OrderLPF ADCDriver ADC CONVST/CSSCLKSDISDO VB Figure47.SimplifiedAnalogFront-EndCircuitSchematic Thedevicecansupportmultipleunipolarorbipolar,single-endedinputvoltagerangesbasedontheconfigurationoftheprogramregisters.AsexplainedintheRANGE_SEL_REGregister,theinputvoltagerangeforeachanalogchannelcanbeconfiguredtobipolar±3×VREF,±2.5×VREF,±1.5×VREF,±1.25×VREF,and±0.625×VREForunipolar0to3×VREF,0to2.5×VREF,0to1.5×VREFand0to1.25×VREF.Withtheinternalorexternalreferencevoltagesetto4.096V,theinputrangesofthedevicecanbeconfiguredtobipolarrangesof±12.288V,±10.24V,±6.144V,±5.12V,and±2.56Vorunipolarrangesof0Vto12.288V,0Vto10.24V,0Vto6.144V,and0Vto5.12V. Thedevicesamplesthevoltagedifference(AIN_P–AIN_GND)betweentheanaloginputandtheAIN_GNDpin.Thedeviceallowsa±0.1-VrangeontheAIN_GNDpin.Thisfeatureisusefulinmodularsystemswherethesensororsignal-conditioningblockisfurtherawayfromtheADContheboardandwhenadifferenceinthegroundpotentialofthesensororsignalconditionerfromtheADCgroundispossible.Insuchcases,runningseparatewiresfromtheAIN_GNDpinofthedevicetothesensororsignal-conditioninggroundismended.Inordertoobtainoptimumperformance,theinputcurrentsandimpedancesalongeachinputpatharemendedtobematched.Thetwosingle-endedsignalstoAIN_PandAIN_GNDmustberoutedassymmetricallyaspossiblefromthesignalsourcetotheADCinputpins. Iftheanaloginputpin(AIN_P)tothedeviceisleftfloating,theoutputoftheADCcorrespondstoaninternalbiasingvoltage.TheoutputfromtheADCmustbeconsideredasinvalidifthedeviceisoperatedwithfloatinginputpins.Thisconditiondoesnotcauseanydamagetothedevice,whichesfullyfunctionalwhenavalidinputvoltageisappliedtothepins. 7.3.2AnalogInputImpedance Thedevicepresentsaresistiveinputimpedance≥1MΩoneachoftheanaloginputs.TheinputimpedanceisindependentoftheADCsamplingfrequencyortheinputsignalfrequency.TheprimaryadvantageofsuchhighimpedanceinputsistheeaseofdrivingtheADCinputswithoutrequiringdrivingamplifierswithlowoutputimpedance.Bipolar,high-voltagepowersuppliesarenotrequiredinthesystembecausethisADCdoesnotrequireanyhigh-voltage,front-enddrivers.Inmostapplications,thesignalsourcesorsensoroutputscanbedirectlyconnectedtotheADCinput,thussignificantlysimplifyingthedesignofthesignalchain. Inordertomaintainthedcuracyofthesystem,matchingtheexternalsourceimpedanceontheAIN_PinputpinwithanequivalentresistanceontheAIN_GNDpinismended.Thismatchinghelpscancelanyadditionaloffseterrorcontributedbytheexternalresistance. Copyright©2016,TexasInstrumentsIncorporated 23 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 FeatureDescription(continued) 7.3.3InputProtectionCircuit Thedevicefeaturesaninternalovervoltageprotection(OVP)circuitoneachoftheanaloginputs.Usetheinternalprotectioncircuitonlyasasecondaryprotectionscheme.Theexternalprotectiondevicesintheendapplicationarehighlymendedtobeusedtoprotectagainstsurges,electrostaticdischarge(ESD),andelectricalfasttransient(EFT)conditions.AconceptualblockdiagramoftheinternalOVPcircuitisshowninFigure48. AVDDVP+ RFB 0V ESD AVDD VP- RS AIN_
P RS AIN_GND 1MŸD1pD2p AVDDD1n V± V+ + 1MŸ D2n RDCESD VOUT VBGND Figure48.InputOvervoltageProtectionCircuitSchematic AsshowninFigure48,binationofthe1-MΩ(or,1.2MΩforappropriateinputranges)inputresistorsalongwiththePGAgain-settingresistorsRFBandRDClimitthecurrentflowingintotheinputpin.binationofanti-paralleldiodes,D1andD2areaddedtoprotecttheinternalcircuitryandsettheovervoltageprotectionlimits. Table1explainsthevariousoperatingconditionsforthedevicewhenpoweredon.Thistableindicatesthatwhenthedeviceisproperlypoweredup(AVDD=5V)oroffersalowimpedanceof<30kΩ,theinternalovervoltageprotectioncircuitcanwithstandupto±20Vontheanaloginputpins. Table1.InputOvervoltageProtectionLimitsWhenAVDD=5VorOffersaLowImpedanceof<30kΩ
(1) INPUTCONDITION(VOVP=±20V) CONDITION RANGE |VIN|<|VRANGE| Withinoperatingrange |VRANGE|<|VIN|<|VOVP| Beyondoperatingrangebutwithinovervoltagerange |VIN|>|VOVP| Beyondovervoltagerange TESTCONDITION Allinputranges Allinputranges Allinputranges ADCOUTPUT COMMENTS ValidSaturatedSaturated Devicefunctionsasperdatasheetspecifications. ADCoutputissaturated,butdeviceisinternallyprotected(notmendedforextendedtime).Thisusageconditioncancauseirreversibledamagetothedevice.
(1)GND=0V,AIN_GND=0V,|VRANGE|isthemaximuminputvoltageforanyselectedinputrange,and|VOVP|isthebreak-downvoltagefortheinternalOVPcircuit.AssumethatRSisapproximately0Ω. 24 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TheresultsindicatedinTable1arebasedonanassumptionthattheanaloginputpinisdrivenbyaverylowimpedancesource(RSisapproximately0Ω).However,ifthesourcedrivingtheinputhashigherimpedance,thecurrentflowingthroughtheprotectiondiodesreducesfurther,therebyincreasingtheOVPvoltagerange.Notethathighersourceimpedancesresultingainerrorsandcontributetooverallsystemnoiseperformance. Figure49showsthevoltageversuscurrentresponseoftheinternalovervoltageprotectioncircuitwhenthedeviceispoweredon.ordingtothiscurrent-to-voltage(I-V)response,thecurrentflowingintothedeviceinputpinislimitedbythe1-MΩ(or1.2MΩforappropriateinputranges)inputimpedance.However,forvoltagesbeyond±20V,theinternalnodevoltagessurpassthebreak-downvoltageforinternaltransistors,thussettingthelimitforovervoltageprotectionontheinputpin. ThesameovervoltageprotectioncircuitalsoprovidesprotectiontothedevicewhenthedeviceisnotpoweredonandAVDDisfloatingwithanimpedance>30kΩ.ThisconditioncanarisewhentheinputsignalsareappliedbeforetheADCisfullypoweredon.TheovervoltageprotectionlimitsforthisconditionareshowninTable2. Table2.InputOvervoltageProtectionLimitsWhenAVDD=FloatingwithImpedance>30kΩ
(1) CONDITION INPUTCONDITION(VOVP=±11V) RANGE |VIN|<|VOVP| Withinovervoltagerange |VIN|>|VOVP| Beyondovervoltagerange TESTCONDITION Allinputranges Allinputranges ADCOUTPUT COMMENTS InvalidInvalid DeviceisnotfunctionalbutisprotectedinternallybytheOVPcircuit. Thisusageconditioncancauseirreversibledamagetothedevice.
(1)AVDD=floating,GND=0V,AIN_GND=0V,|VRANGE|isthemaximuminputvoltageforanyselectedinputrange,and|VOVP|isthebreak-downvoltagefortheinternalOVPcircuit.AssumethatRSisapproximately0Ω. Figure50showstheI-Vresponseoftheinternalovervoltageprotectioncircuitwhenthedeviceisnotpoweredon.ordingtothisI-Vresp
此类器件采用高速高精度SARADC、集成模拟前端(AFE)输入驱动器电路、高达±20V的过压保护电路以及一个温度漂移极低的4.096V片上基准。
此类器件由5V模拟单电源供电，但支持±12.288V、±6.144V、±10.24V、±5.12V和±2.56V实际双极输入范围以及0V至12.288V、0V至10.24V、0V至6.144V和0V至5.12V单极输入范围。
各输入范围的增益和偏移误差均可在特定数值范围内进行调节，确保直流精度较高。
通过针对器件内部寄存器进行编程可选择输入范围。
该器件提供恒定阻性输入阻抗(≥1MΩ)，不受所选输入范围的影响。
multiSPI数字接口向后兼容传统SPI协议。
此外，该器件的可配置特性便于连接各种主机控制器。
器件型号ADS868x 器件信息
(1) 封装TSSOP(16)WQFN(16) 封装尺寸（标称值）5.00mmx4.40mm4.00mmx4.00mm
(1)要了解所有可用封装，请见数据表末尾的可订购产品附录。
AVDD DVDD方框图 ADS868x 4.096-VReference REFIOREFCAP AIN_PAIN_GND 1M:1M: OVPOVP PGA 2nd-OrderLPF ADCDriver VBIAS Oscillator 16-BitSARADC DigitalLogicandInterface CONVST/CSSCLKSDISDO AGND DGND REFGNDCopyright©2016,TexasInstrumentsIncorporated
1 AnIMPORTANTNOTICEattheendofthisdatasheetaddressesavailability,warranty,changes,useinsafety-criticalapplications, intellectualpropertymattersandotherimportantdisclaimers.PRODUCTIONDATA. EnglishDataSheet:SBAS633 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 目录 1特性..........................................................................12应用..........................................................................13说明..........................................................................14修订历史记录...........................................................25PinConfigurationandFunctions.........................46Specifications.........................................................5 6.1AbsoluteMaximumRatings......................................56.2ESDRatings..............................................................56.3mendedOperatingConditions.......................56.4ThermalInformation..................................................56.5ElectricalCharacteristics...........................................66.6TimingRequirements:ConversionCycle................106.7TimingRequirements:AsynchronousReset...........106.8TimingRequirements:SPI-CompatibleSerial Interface...................................................................106.9TimingRequirements:Source-SynchronousSerial Interface(ExternalClock)........................................116.10TimingRequirements:Source-SynchronousSerial Interface(InternalClock)..........................................116.11TypicalCharacteristics..........................................157DetailedDescription............................................227.1Overview.................................................................227.2FunctionalBlockDiagram.......................................22 7.3FeatureDescription.................................................237.4DeviceFunctionalModes........................................357.5Programming...........................................................407.6RegisterMaps.........................................................488ApplicationandImplementation........................568.1ApplicationInformation............................................568.2TypicalApplication.................................................569PowerSupplymendations......................609.1PowerSupplyDecoupling.......................................609.2PowerSaving..........................................................6010Layout...................................................................6110.1LayoutGuidelines.................................................6110.2LayoutExample....................................................6211器件和文档支持.....................................................6311.1文档支持................................................................6311.2相关链接................................................................6311.3接收文档更新通知.................................................6311.4社区资源................................................................6311.5商标.......................................................................6311.6静电放电警告.........................................................6311.7Glossary................................................................6312机械、封装和可订购信息.......................................64 4修订历史记录 注：之前版本的页码可能与当前版本有所不同。
ChangesfromRevisionA(March2016)toRevisionB Page •已添加ADS8685和ADS8689器件至文档
............................................................................................................................
1•已更改特性要点；增加了高速要点，删除了聚合吞吐量分项（性能优异要点），已添加扩展温度范围至工业温度范围 要点，删除了封装要点............................................................................................................................................................
1•已更改（说明部分..................................................................................................................................................................
1•DeletedDeviceComparisonTable........................................................................................................................................
4•AddedmaximumthroughputtoconditionsstatementofElectricalCharacteristicstableandallTimingRequirements tables.....................................................................................................................................................................................
6•ChangedPower-SupplyRequirementssub-sectionparameternamesinElectricalCharacteristicstableforclarity (specificationvaluesdidnotchange).....................................................................................................................................
8•ChangedconditionsofTimingRequirementstables...........................................................................................................
10•ChangedTypicalCharacteristicssection:addedmaximumthroughputtoconditionsstatementanddeleted redundantplotsfortheADS868x........................................................................................................................................
15•ChangedInputAlarmsection:correctedalarmresetconfigurationinlasttwoparagraphsandbothimages.....................34•AddedfifthparagraphofMultipleDevices:Daisy-ChainTopologysection..........................................................................37•AddedRST(FallingEdge)toDeviceFunctionalStatesfigure............................................................................................
38•ChangedbulletedlistinDataTransferFramesectionpertainingtotheendofthedatatransferframeF..........................41•ChangedOutputDataWordsection.....................................................................................................................................
43•ChangedseveralvalueafterresetnotationsfromhtobthroughoutbitregistersoftheRegisterMapssection...............48•ChangedALARM_H_TH_REGRegisterFieldDescriptionstable......................................................................................55•ChangedALARM_L_TH_REGRegisterFieldDescriptionstable.......................................................................................55•ChangedApplicationandImplementationsectionforclarityandimproveddescriptionofdevicefunctionality.................56•ChangedfirstsentenceofPowerSavingsection.................................................................................................................
602 版权©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 ChangesfromOriginal(February2016)toRevisionA Page •已发布为量产数据
...................................................................................................................................................................
1 Copyright©2016,TexasInstrumentsIncorporated
3 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 5PinConfigurationandFunctions PWPackage16-PinTSSOPTopView(NottoScale) DGND1AVDD2AGND3REFIO4REFGND5REFCAP6AIN_P7AIN_GND8 16DVDD15RVS14ALARM/SDO-1/GPO13SDO-012SCLK11CONVST/CS10SDI9RST AGNDREFIOREFGNDREFCAP AVDDDGNDDVDDRVS RUMPackage16-PinWQFNTopView(NottoScale) ALARM/SDO-1/GPOSDO-0SCLKCONVST/CS AIN_PAIN_GND RSTSDI NAMEAGNDAIN_GNDAIN_PALARM/SDO-1/GPOAVDD CONVST/CS DGNDDVDDREFCAPREFGNDREFIORSTRVS SCLKSDISDO-
0 NO. TSSOP WQFN
3 1
8 6
7 5 14 12
2 16 11
9 1 15 16 14
6 4
5 3
4 2
9 7 15 13 12 10 10
8 13 11 TYPE
(1) PinFunctions DESCRIPTION
P Analoggroundpin.DecouplewiththeAVDDpin. AI Analoginput:negative.DecouplewiththeAIN_Ppin. AI Analoginput:positive.DecouplewiththeAIN_GNDpin. DO Multi-functionoutputpin.Activehighalarm. Dataoutput1formunication.General-purposeoutputpin.
P Analogsupplypin.DecouplewiththeAGNDpin. Dual-functionalitypin. Activehighlogic:conversionstartinputpin;aCONVSTrisingedgebringsthedevicefrom DI acquisitionphasetoconversionphase. Activelowlogic:chip-selectinputpin;thedevicetakescontrolofthedatabuswhenCSislow; theSDO-xpinsgototri-statewhenCSishigh.
P Digitalgroundpin.DecouplewiththeDVDDpin.
P Digitalsupplypin.DecouplewiththeDGNDpin. AO ADCreferencebufferdecouplingcapacitorpin.DecouplewiththeREFGNDpin.
P Referencegroundpin;shorttotheanaloggroundplane.DecouplewiththeREFIOand REFCAPpins. AIOInternalreferenceoutputandexternalreferenceinputpin.DecouplewithREFGND. DI Activelowlogicinputtoresetthedevice. Multi-functionoutputpinforserialinterface;seetheRESETStatesection. DO WithCSheldhigh,RVSreflectsthestatusoftheinternalADCSTsignal. WithCSlow,thestatusofRVSdependsontheoutputprotocolselection. DI munication:clockinputpinfortheserialinterface. Allsystem-synchronousdatatransferprotocolsaretimedwithrespecttotheSCLKsignal. DI Dualfunction:datainputpinformunication. Chaindatainputduringmunicationindaisy-chainmode. DO munication:dataoutput0
(1)AI=analoginput,AIO=analoginput/output,DI=digitalinput,DO=digitaloutput,andP=powersupply.
4 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 6Specifications 6.1AbsoluteMaximumRatings overoperatingfree-airtemperaturerange(unlessotherwisenoted)
(1) AIN_
P,AIN_GNDtoGND AVDD=5V
(2)AVDD=floating
(3) AVDDtoGNDorDVDDtoGND REFCAPtoREFGNDorREFIOtoREFGND GNDtoREFGND DigitalinputpinstoGND DigitaloutputpinstoGND Temperature Operating,TAStorage,Tstg MIN MAX UNIT –20 20
V –11 11 –0.3
7 V –0.3 5.7
V –0.3 0.3
V –0.3 DVDD
+0.3
V –0.3 DVDD+0.3
V –40 125 °
C –65 150
(1)StressesbeyondthoselistedunderAbsoluteMaximumRatingsmaycausepermanentdamagetothedevice.Thesearestressratingsonly,anddonotimplyfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedundermendedOperatingConditions.Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability.
(2)AVDD=5Voffersalowimpedanceof<30kΩ.
(3)AVDD=floatingwithanimpedance>30kΩ. 6.2ESDRatings V(ESD) Electrostaticdischarge AnaloginputpinsHumanbodymodel(HBM),perANSI/ESDA/JEDECJS-001
(1)(AIN_
P,AIN_GND) Allotherpins Chargeddevicemodel(CDM),perJEDECspecificationJESD22-C101
(2)
(1)JEDECdocumentJEP155statesthat500-VHBMallowssafemanufacturingwithastandardESDcontrolprocess.
(2)JEDECdocumentJEP157statesthat250-VCDMallowssafemanufacturingwithastandardESDcontrolprocess. VALUE±4000±2000±500 UNITV 6.3mendedOperatingConditions overoperatingfree-airtemperaturerange(unlessotherwisenoted) MIN AVDD Analogsupplyvoltage 4.75 DVDD Digitalsupplyvoltage 1.65 NOM5 3.3 MAX5.25AVDD UNITVV 6.4ThermalInformation THERMALMETRIC
(1) RθJARθ)RθJBψJTψJBRθJC(bot) Junction-to-ambientthermalresistanceJunction-to-case)thermalresistanceJunction-to-boardthermalresistancecharacterizationparameterJunction-to-boardcharacterizationparameterJunction-to-case(bottom)thermalresistance ADS8681,ADS8685,ADS8689 PW(TSSOP)RUM(WQFN) 16PINS 16PINS 95.7 31.9 29.3 27.9 41.5 7.4 1.5 0.3 40.8 7.4 N/A 1.9 UNIT °C/W°C/W°C/W°C/W°C/W°C/W
(1)Formoreinformationabouttraditionalandnewthermalmetrics,seetheSemiconductorandICPackageThermalMetricsapplicationreport. Copyright©2016,TexasInstrumentsIncorporated
5 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 6.5ElectricalCharacteristics allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) PARAMETER TESTCONDITIONS MIN TYP MAXUNIT ANALOGINPUTS Inputrange=±3×VREF –12.288 12.288 Inputrange=±2.5×VREF –10.24 10.24 Inputrange=±1.5×VREF –6.144 6.144 Full-scaleinputspan
(1) VIN (AIN_PtoAIN_GND) Inputrange=±1.25×VREFInputrange=±0.625×VREFInputrange=3×VREF –5.12–2.56
0 5.12 2.56
V 12.288 Inputrange=2.5×VREF
0 10.24 Inputrange=1.5×VREF
0 6.144 Inputrange=1.25×VREF
0 5.12 Inputrange=±3×VREF –12.288 12.288 Inputrange=±2.5×VREF –10.24 10.24 Inputrange=±1.5×VREF –6.144 6.144 Inputrange=±1.25×VREF –5.12 5.12 AIN_
P Operatinginputrange Inputrange=±0.625×VREF –2.56 2.56
V Inputrange=3×VREF
0 12.288 Inputrange=2.5×VREF
0 10.24 Inputrange=1.5×VREF
0 6.144 Inputrange=1.25×VREF
0 5.12 AIN_GND Operatinginputrange Allinputranges –0.1
0 0.1
V Inputrange=±3×VREF 1.02 1.2 1.38 Inputrange=±1.5×VREF 1.02 1.2 1.38 Inputrange=3×VREF 1.02 1.2 1.38 Inputrange=1.5×VREF 1.02 1.2 1.38 RIN Inputimpedance AtTA=25°CInputrange=±2.5×VREF 0.85
1 1.15MΩ Inputrange=±1.25×VREF 0.85
1 1.15 Inputrange=±0.625×VREF 0.85
1 1.15 Inputrange=2.5×VREF 0.85
1 1.15 Inputrange=1.25×VREF 0.85
1 1.15 Inputimpedancedrift
7 25ppm/°
C Inputrange=±3×VREF (VIN–2.5)/RIN Inputrange=±2.5×VREF (VIN–2.2)/RIN Inputrange=±1.5×VREF (VIN–2.0)/RIN IIN Inputcurrent WithvoltageattheAIN_Ppin=VIN Inputrange=±1.25×VREFInputrange=±0.625×VREFInputrange=3×VREF (VIN–2.0)/RIN (VIN–1.6)/RIN µ
A (VIN–2.6)/RIN Inputrange=2.5×VREF (VIN–2.5)/RIN Inputrange=1.5×VREF (VIN–2.7)/RIN Inputrange=1.25×VREF (VIN–2.5)/RIN INPUTOVERVOLTAGEPROTECTIONCIRCUIT VOVP Allinputranges AVDD=5Vorofferslowimpedance<30kΩ, –20 allinputranges AVDD=floatingwithimpedance>30kΩ, –11 allinputranges 20V 11 INPUTBANDWIDTH f–3dBf–0.1dB Small-signalInputbandwidth –3dB–0.1dB AllinputrangesAllinputranges 15kHz 2.5
(1)Idealinputspan,doesnotincludegainoroffseterror.
6 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 ElectricalCharacteristics(continued) allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) PARAMETER TESTCONDITIONS MIN TYP MAXUNIT SYSTEMPERFORMANCE Resolution 16 Bits NMC Nomissingcodes 16 Bits DNL Differentialnonlinearity
(2) Allinputranges –0.7 ±0.4 0.7LSB Allbipolarranges
(3) –1.2 ±0.5 1.2 INL Integralnonlinearity
(2) Allunipolarranges
(4) ADS8681ADS8685,ADS8689 –1.5 ±0.5 –1.2 ±0.5 1.5LSB1.2 EO Offseterror
(5) AtTA=25°
C Allbipolarranges
(3)Allunipolarranges
(4) –
1 ±0.2 –
2 ±0.2 1mV
2 Offseterrordriftwithtemperature Allinputranges –
3 ±0.75 3ppm/°
C EG Gainerror
(6) AtTA=25°C,allinputranges Gainerrordriftwithtemperature
(7) Allinputranges –0.025–
5 ±0.01±
1 0.0255 %FSRppm/°
C DYNAMICCHARACTERISTICS Inputrange=±3×VREF ADS8681ADS8685,ADS8689 90.25 92 90.5 92 Inputrange=±2.5×VREF ADS8681ADS8685,ADS8689 90.25 92 90.5 92 SNR Signal-to-noiseratio
(8) Inputrange=±1.5×VREFInputrange=±1.25×VREF 89.5 91.5 89.5 91.5 dB Inputrange=±0.625×VREF 87.75 90 Inputrange=3×VREF 89.25 91 Inputrange=2.5×VREF 89 91 Inputrange=1.5×VREF 88 90 Inputrange=1.25×VREF 87.5 90 THD Totalharmonicdistortion
(9)(8) Allinputranges ADS8681ADS8685,ADS8689 –107dB –112 Inputrange=±3×VREF ADS8681ADS8685,ADS8689 90.15 92 90.4 92 Inputrange=±2.5×VREF ADS8681ADS8685,ADS8689 90.15 92 90.4 92 SINAD Signal-to-noise+distortion
(8) Inputrange=±1.5×VREFInputrange=±1.25×VREF 89.4 91.5 89.4 91.5 dB Inputrange=±0.625×VREF 87.65 90 Inputrange=3×VREF 89 91 Inputrange=2.5×VREF 88.75 91 Inputrange=1.5×VREF 87.75 90 Inputrange=1.25×VREF 87.25 90 SFDR Spurious-freedynamicrange
(8) Allinputranges ADS8681ADS8685,ADS8689 109dB 114
(2)ThisspecificationindicatestheendpointINL,notbest-fitINL.
(3)Bipolarrangesare±12.288V,±10.24V,±6.144V,±5.12V,and±2.56V.
(4)Unipolarrangesare0V–12.288V,0V–10.24V,0V–6.144V,and0V–5.12V.
(5)Measuredrelativetoactualmeasuredreference.
(6)Excludesinternalreferenceuracyerror.
(7)Excludesinternalreferencetemperaturedrift.
(8)Allspecificationsexpressedindecibels(dB)refertothefull-scaleinput(FSR)andaretestedwitha1-kHzinputsignal0.25dBbelow full-scale,unlessotherwisespecified.
(9)Calculatedonthefirstnineharmonicsoftheinputfrequency. Copyright©2016,TexasInstrumentsIncorporated
7 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 ElectricalCharacteristics(continued) allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) PARAMETER TESTCONDITIONS MIN TYP MAXUNIT SAMPLINGDYNAMICS ADS8681 665 tCONV Conversiontime ADS8685 1000ns ADS8689 5000 ADS8681 335 tACQ Acquisitiontime ADS8685 1000 ns ADS8689 5000 fcycleMwiathxoimutulmatethnrcoyughputrate ADS8681ADS8685ADS8689 1000500100 kSPS INTERNALREFERENCEOUTPUT VREFIO OntheREFIOpin(configuredasanoutput) AtTA=25°
C TSSOP(PW)WQFN(RUM) 4.095 4.096 4.097
V 4.094 4.096 4.098 dVREFIO/dTA Internalreferencetemperaturedrift TSSOP(PW)WQFN(RUM)
4 7 ppm/°
C 5 COUT_REFIO DecouplingcapacitoronREFIOpin 4.7 µ
F VREFCAP ReferencevoltagetotheADC(ontheREFCAPpin) AtTA=25°
C 4.095 4.096 4.097
V REFCAPtemperaturedrift 0.5 2ppm/°
C COUT_REFCAP DecouplingcapacitoronREFCAPpin 10 μ
F Turn-ontime COUT_REFCAP=10µ
F,COUT_REFIO=10µ
F 20 ms EXTERNALREFERENCEINPUT VREFIO_EXT ExternalreferencevoltageonREFIOREFIOpinconfiguredasaninput 4.046 4.096 4.146
V AVDDCOMPARATOR VTH_HIGH Highthresholdvoltage 5.3
V VTH_LOW Lowthresholdvoltage 4.7
V POWER-SUPPLYREQUIREMENTS AVDD Analogpower-supplyvoltage 4.75
5 5.25 DVDD Digitalpower-supplyvoltage OperatingrangeSupplyrangeforspecifiedperformance 1.65 3.3AVDD
V 2.7 3.3AVDD IAVDD_DYN Analogsupplycurrent,deviceconvertingatmaximumthroughput Internalreference Externalreference ADS8681ADS8685ADS8689ADS8681ADS8685ADS8689 8.2 10.5 5.6 7.25
4 5 mA 7.0 8.75 4.4 5.5 2.7 3.25 IAVDD_STC Analogsupplycurrent,devicenotconverting Internalreference Externalreference ADS8681ADS8685,ADS8689ADS8681ADS8685,ADS8689 4.7 6.25 3.5 4.7 mA 3.5 4.5 2.3
3 IAVDD_STDBY Analogsupplycurrent,deviceinSTANDBYmode InternalreferenceExternalreference 2.8mA 1.6 IAVDD_PD Analogsupplycurrent,deviceinPDmode InternalreferenceExternalreference 10μA 10 IDVDD_DYN Digitalsupplycurrent,maximumthroughput 0.2 0.25mA IDVDD_STDBY Digitalsupplycurrent,deviceinSTANDBYmode
1 μ
A IDVDD_PD Digitalsupplycurrent,deviceinPDmode
1 μ
A 8 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 ElectricalCharacteristics(continued) allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) PARAMETER TESTCONDITIONS MIN TYP MAXUNIT DIGITALINPUTS(CMOS) DVDD>2.35V VIH Digitalhighinputvoltagelogiclevel DVDD≤2.35V 0.7×DVDD 0.8×DVDD DVDD+0.3V DVDD+0.3 DVDD>2.35V VIL Digitallowinputvoltagelogiclevel DVDD≤2.35V –0.3 0.3× DVDD
V –0.3 0.2× DVDD Inputleakagecurrent 100 nA Inputpincapacitance
5 pF DIGITALOUTPUTS(CMOS) VOH DigitalhighoutputvoltagelogiclevelIO=500-μAsource 0.8×DVDD DVDD
V VOL Digitallowoutputvoltagelogiclevel IO=500-μAsink
0 0.2×
V DVDD Floatingstateleakagecurrent Onlyfordigitaloutputpins
1 µ
A Internalpincapacitance
5 pF TEMPERATURERANGE TA Operatingfree-airtemperature –40 125°
C Copyright©2016,TexasInstrumentsIncorporated
9 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 6.6TimingRequirements:ConversionCycle allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) MIN TYP MAXUNIT TIMINGREQUIREMENTS ADS8681 1000 fcycle Samplingfrequency ADS8685 500kSPS ADS8689 100 tcycle ADCcycletimeperiod 1/fcycle ADS8681 335 tacq Acquisitiontime ADS8685 1000 ns ADS8689 5000 TIMINGSPECIFICATIONS ADS8681 665 tconv Conversiontime ADS8685 1000ns ADS8689 5000 6.7TimingRequirements:AsynchronousReset allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) MIN TYP MAXUNIT TIMINGREQUIREMENTS twl_RST Pulseduration:RSThigh 100 ns TIMINGSPECIFICATIONS tD_RST_PORDelaytimeforPORreset:RSTrisingtoRVSrising 20 ms tD_RST_APPDelaytimeforapplicationreset:RSTrisingtoCONVST/CSrising
1 µs tNAP_WKUPWake-uptime:NAPmode 20 µs tPWRUP Power-uptime:PDmode 20 ms 6.8TimingRequirements:SPI-CompatibleSerialInterface allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) MIN TYP MAXUNIT TIMINGREQUIREMENTS fCLK Serialclockfrequency 66.67MHz tCLK Serialclocktimeperiod 1/fCLK tPH_CK SCLKhightime 0.45 0.55 tCLK tPL_CK SCLKlowtime 0.45 0.55 tCLK tSU_CSCK Setuptime:CONVST/CSfallingtofirstSCLKcaptureedge 7.5 ns tSU_CKDI Setuptime:SDIdatavalidtoSCLKcaptureedge 7.5 ns tHT_CKDI Holdtime:SCLKcaptureedgeto(previous)datavalidonSDI 7.5 ns tHT_CKCS Delaytime:lastSCLKcaptureedgetoCONVST/CSrising 7.5 ns TIMINGSPECIFICATIONS tDEN_CSDODelaytime:CONVST/CSfallingedgetodataenable 9.5 ns tDZ_CSDO Delaytime:CONVST/CSrisingtoSDO-xgoingto3-state 10 ns tD_CKDO Delaytime:SCLKlaunchedgeto(next)datavalidonSDO-x 12 ns tD_CSRVS Delaytime:CONVST/CSrisingedgetoRVSfalling 14 ns 10 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 6.9TimingRequirements:Source-SynchronousSerialInterface(ExternalClock) allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) MIN TYP MAXUNIT TIMINGREQUIREMENTS fCLK Serialclockfrequency 66.67MHz tCLK Serialclocktimeperiod 1/fCLK tPH_CK SCLKhightime 0.45 0.55tCLK tPL_CK SCLKlowtime 0.45 0.55tCLK TIMINGSPECIFICATIONS tDEN_CSDODelaytime:CONVST/CSfallingedgetodataenable 9.5ns tDZ_CSDODelaytime:CONVST/CSrisingtoSDO-xgoingto3-state 10ns tD_CKRVS_rDelaytime:SCLKrisingedgetoRVSrising 14ns tD_CKRVS_fDelaytime:SCLKfallingedgetoRVSfalling 14ns tD_RVSDODelaytime:RVSrisingto(next)datavalidonSDO-x 2.5ns tD_CSRVSDelaytime:CONVST/CSrisingedgetoRVSdisplayinginternaldevicestate 15ns 6.10TimingRequirements:Source-SynchronousSerialInterface(InternalClock) allminimumandmaximumspecificationsareatTA=–40°Cto+125°C;typicalspecificationsareatTA=25°C;AVDD=5V,DVDD=3.3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) MIN TYP MAXUNIT TIMINGSPECIFICATIONS tDEN_CSDODelaytime:CONVST/CSfallingedgetodataenable 9.5 ns tDZ_CSDO Delaytime:CONVST/CSrisingtoSDO-xgoingto3-state 10 ns tDEN_CSRVSDelaytime:CONVST/CSfallingedgetofirstrisingedgeonRVS 50 ns tD_RVSDODelaytime:RVSrisingto(next)datavalidonSDO-x 2.5 ns tINTCLK Timeperiod:internalclock 15 ns tCYC_RVS Timeperiod:RVSsignal 15 ns tWH_RVS RVShightime 0.4 0.6tINTCLK tWL_RVS RVSlowtime 0.4 0.6tINTCLK tD_CSRVS Delaytime:CONVST/CSrisingedgetoRVSdisplayinginternaldevicestate 15 ns Copyright©2016,TexasInstrumentsIncorporated 11 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 CONVST/CSADCST(Internal) tcycletconv TheCSfallingedgecanbeissuedaftertconv_maxorwhenRVSgoeshigh. tacq RVS Figure1.ConversionCycleTimingDiagram RSTRVS trsttwl_RST td_rst Figure2.AsynchronousResetTimingDiagram CONVST/CSRVS tconv_maxtD_CSRVS SCLK CPOL=0CPOL=
1 tcycle DataReadTime tD_CSRVStSU_CSCK tHT_CKCS SDO-0SDI tDEN_CSDO tD_CKDO tD_CSDO
M M-
1 M-
2 L+
1 L tSU_CKDI tHT_CKDI Figure3.StandardSPIInterfaceTimingDiagramforCPHA=
0 12 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 tconv_max tcycleDataReadTime CONVST/CS RVS tD_CSRVS SCLK CPOL=0CPOL=
1 tD_CSRVStSU_CSCK tHT_CKCS SDO-0SDI tDEN_CSDO 0MtSU_CKDI tD_CKDO M-
1 L+1L tHT_CKDI tDZ_CSDO Figure4.StandardSPIInterfaceTimingDiagramforCPHA=
1 CONVST/CSRVS tconv_maxtD_CSRVS SCLK CPOL=0CPOL=
1 tcycle DataReadTime tD_CSRVStSU_CSCK tHT_CKCS SDO-
0 tDEN_CSDO tD_CKDO tD_CSDO
M M-
2 M-
4 L+
3 L+
1 SDO-1SDI M-
1 M-
3 M-
5 L+
2 L tSU_CKDI tHT_CKDI Figure5.multiSPIInterfaceTimingDiagramforDualSDO-xandCPHA=
0 Copyright©2016,TexasInstrumentsIncorporated 13 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 CONVST/CSRVS tconv_maxtD_CSRVS SCLK CPOL=0CPOL=
1 SDO-
0 tDEN_CSDO tcycleDataReadTime tD_CSRVStSU_CSCK tHT_CKCS tD_CKDO tDZ_CSDO
0 M M-
2 L+3L+
1 SDO-
1 0 M-
1 M-
1 L+
2 L tSU_CKDI tHT_CKDI SDI Figure6.multiSPIInterfaceTimingDiagramforDualSDO-xandCPHA=
1 CONVST/CSSCLKSDO-0RVS tconvtD_CSRD DataReadTime tSU_CSCK tDEN_CSDO M tD_CKRVS_f tD_RVSDO M-
1 M-kM-k-1M-k-
2 L+
1 tD_CKRVS_r L tD_CSRVS tDZ_CSDO Figure7.multiSPISource-SynchronousExternalClockSerialInterfaceTimingDiagram CONVST/CS tconv_max DataReadTime SCLK tDEN_CSDO SDO-
0 M M-
1 M-kM-k-1M-k-
2 L+
1 L tDEN_CSRVS tD_RVSDO tWH_RVS tD_CSRVS RVS tCYC_RVS tWL_RVS Figure8.multiSPISource-SynchronousInternalClockSerialInterfaceTimingDiagram tDZ_CSDO 14 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 6.11TypicalCharacteristics atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 15 ±12.288V ±10.24V
9 ±6.144V ±5.12V ±2.56V 0-12.288V
3 0-10.24V 0-6.144V 0-5.12V -
3 15 -40C 25C
9 125C
3 -
3 AnalogInputCurrent(uA) AnalogInputCurrent(uA) -
9 -
9 InputImpedanceDrift(ppm) -15-12.288-8.192 -4.096
0 4.096 InputVoltage(V) 8.192 12.288 D001 Figure9.InputI-VCharacteristicAcrossInputRanges 400 200
0 -200 -400-40 ±12.288V±10.24V±6.144V±5.12V±2.56V 0-12.288V0-10.24V0-6.144V0-5.12V -
7 26 59 92 Free-AirTemperature(qC) 125 D003 Figure11.InputImpedanceDriftvsTemperature 45000 40000 35000 30000 25000 20000 15000 10000 5000
0 327663276732768327693277032771 OutputCodes D007 Mean=32768.24,sigma=0.57,input=0V Figure13.DCHistogramforMid-ScaleInputs(±12.288V) NumberofHits NumberofDevices -15-12.288-8.192 -4.096
0 4.096 InputVoltage(V) Range=±12.288V 8.192 12.288 D002 Figure10.InputI-VCharacteristicAcrossTemperature 1600 1400 1200 1000 800 600 400 200 01.021.061.11.141.181.221.261.3InputImpedance(M:) Numberofsamples=3398 1.341.38 D004 Figure12.TypicalDistributionofInputImpedance 45000 40000 35000 30000 25000 20000 15000 10000 5000
0 327663276732768327693277032771 OutputCodes D0083 Mean=32767.24,sigma=0.56,input=0V Figure14.DCHistogramforMid-ScaleInputs(±10.24V) NumberofHits Copyright©2016,TexasInstrumentsIncorporated 15 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 40000 45000 NumberofHits 300002000010000 NumberofHits 3000015000 NumberofHits
0 32766327673276832769327703277132772 OutputCodes D009 Mean=32768.21,sigma=0.62,input=0V Figure15.DCHistogramforMid-ScaleInputs(±6.144V) 36000 30000 24000 18000 12000 6000
0 3276532766327673276832769327703277132772 OutputCodes D011 Mean=32768.22,sigma=0.75,input=0V 40000 Figure17.DCHistogramforMid-ScaleInputs(±2.56V) NumberofHits
0 32766327673276832769327703277132772 OutputCodes D010 Mean=32768.11,sigma=0.62,input=0V Figure16.DCHistogramforMid-ScaleInputs(±5.12V) 50000 40000 30000 20000 10000
0 32765327663276732768327693277032771 OutputCodes D012 Mean=32767.73,sigma=0.60,input=6.144V 40000 Figure18.DCHistogramforMid-ScaleInputs(0V–12.288V) 30000 30000 NumberofHits NumberofHits 20000 20000 10000 10000
0 32766327673276832769327703277132772 OutputCodes D013 Mean=32768.41,sigma=0.62,input=5.12V Figure19.DCHistogramforMid-ScaleInputs(0V–10.24V)
0 32766327673276832769327703277132772 OutputCodes D014 Mean=32768.42,sigma=0.76,input=3.072V Figure20.DCHistogramforMid-ScaleInputs(0V–6.144V) 16 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 40000 0.7 DifferentialNonlinearity(LSB) 0.530000 0.3 NumberofHits 0.120000 -0.1 10000-0.3-0.5 DifferentialNonlinearity(LSB)
0 32766327673276832769327703277132772 OutputCodes D015 Mean=32768.32,sigma=0.78,input=2.56V Figure21.DCHistogramforMid-ScaleInputs(0V–5.12V) 0.7 Maximum 0.5 Minimum 0.3 0.1 -0.1 -0.3 -0.5 IntegralNonlinearity(LSB) -0.70 1.20.80.4 0-0.4-0.8 16384 32768Codes(LSB) Allinputranges 49152 Figure22.TypicalDNLforAllCodes 65535 D016 -0.7-40 1.51 0.5 -
7 26 59 92 Free-AirTemperature(0C) Allinputranges Figure23.DNLvsTemperature 125 D017 -1.20 16384 32768Codes(LSB) 49152 65535 D018 Figure24.TypicalINLforAllCodes(AllBipolarRanges) 1.2MaximumMinimum 0.6 IntegralNonlinearity(LSB) IntegralNonlinearity(LSB)
0 0 -0.5-0.6 -
1 -1.50 16384 32768Codes(LSB) 49152 65536 D023 -1.2-40 -
7 26 59 92 Free-AirTemperature(0C) 125 D027 Figure25.TypicalINLforAllCodes(AllUnipolarRanges) Figure26.INLvsTemperature(AllBipolarRanges) Copyright©2016,TexasInstrumentsIncorporated 17 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 1.5
1 Maximum ±12.288V ±5.12V 0-10.24V Minimum 0.75 ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V 0.75 0.5 OffsetError(mV) IntegralNonlinearity(LSB) 0.25
0 0 -0.25 -0.75 -0.5 -0.75 -1.5-40 -
7 26 59 92 Free-AirTemperature(0C) 125 D032 -1-40 -
7 26 59 92 Free-AirTemperature(0C) 125 D036 Figure27.INLvsTemperature(AllUnipolarRanges) 12.510 0.0250.015 Figure28.OffsetErrorvsTemperatureAcrossInputRanges ±12.288V±10.24V±6.144V ±5.12V±2.56V0-12.288V 0-10.24V0-6.144V0-5.12V GainError(%FSR) NumberofDevices 7.5 0.005
5 -0.005 2.5 -0.015
0 00.20.40.60.811.21.41.61.82.02.22.42.62.83 OffsetDrift(ppm/ºC) D037 -0.025-40 -
7 26 59 92 Free-AirTemperature(0C) 125 D038 NumberofUnits Figure29.TypicalHistogramforOffsetDrift 25 20 15 10
5 0 00.511.522.533.544.55 GainDrift(ppm/ºC) D039 GainError(%FSR) Figure30.GainErrorvsTemperatureAcrossInputRanges 1.11 0.90.80.70.60.50.40.30.20.1 0-0.1
0 ±12.288V±10.24V±6.144V±5.12V±2.56V0-12.288V0-10.24V0-6.144V0-5.12V 2000 4000 6000 SourceResistance(:) 8000 10000 D040 Figure31.TypicalHistogramforGainErrorDrift Figure32.GainErrorvsExternalResistance(REXT) 18 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted)
0 0 -40 -40 Amplitude(dB) Amplitude(dB) -80 -80 -120 -120 -160 -160 -2000 100000 200000300000InputFrequency(Hz) 400000 Numberofpoints=64k,fIN=1kHz 500000 D041 Figure33.TypicalFFTPlot(AllRanges)fortheADS8681
0 -40 -80 -120 -160 Signal-to-NoiseRatio(dB) -2000 50000 100000150000InputFrequency(Hz) 200000 Numberofpoints=64k,fIN=1kHz 250000 D001 Figure34.TypicalFFTPlot(AllRanges)fortheADS8685 94.5 ±12.288V ±5.12V 0-10.24V ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V 93 91.5 90 Amplitude(dB) Signal-to-NoiseRatio(dB) -2000 20000 40000 60000 InputFrequency(Hz) 80000 Numberofpoints=64k,fIN=1kHz 100000 D002 Figure35.TypicalFFTPlot(AllRanges)fortheADS8689 96 ±12.288V ±5.12V 0-10.24V 95 ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V 94 93 92 91 90 89 88-40 -
7 26 59 92 Free-AirTemperature(0C) fIN=1kHz 125 D051 Figure37.SNRvsTemperature Signal-to-Noise+DistortionRatio(dB) 88.5100 1000InputFrequency(Hz) 10000 D050 94939291908988 100 Figure36.SNRvsInputFrequency ±12.288V±10.24V±6.144V ±5.12V±2.56V0-12.288V 0-10.24V0-6.144V0-5.12V 1000InputFrequency(Hz) 10000 D052 Figure38.SINADvsInputFrequency Copyright©2016,TexasInstrumentsIncorporated 19 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) TotalHarmonicDistortionRatio(dB) Signal-to-Noise+DistortionRatio(dB) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 96 ±12.288V ±5.12V 0-10.24V 95 ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V -80 ±12.288V ±5.12V 0-10.24V ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V 94 -90 93 92 -100 91 90 -110 89 88-40 -
7 26 59 92 Free-AirTemperature(0C) fIN=1kHz 125 D053 -120100 1000InputFrequency(Hz) 10000 D054 Figure39.SINADvsTemperature -80 ±12.288V ±5.12V 0-10.24V ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V -90 Figure40.THDvsInputFrequency 987 IAVDDDynamic(mA) TotalHarmonicDistortion(dB)
6 -100
5 4 -110 -120-40 -
7 26 59 92 Free-AirTemperature(0C) fIN=1kHz 125 D055
3 ADS8681
2 ADS8685 ADS8689
1 -40 -
7 26 59 92 125 Free-AirTemperature(qC) D003 Figure41.THDvsTemperature
9 Figure42.AVDDCurrentvsTemperature
5 8 4.57 IAVDDStatic(mA) IAVDDCurrent(mA)
6 4
5 4 3.5
3 2 ADS8681 ADS8685
1 0 200 400 600 800 1000 Throughput(ksps) D005 3 2.5-40 ADS8681ADS8685ADS8689 -
7 26 59 92 Free-AirTemperature(qC) 125 D004 Figure43.AVDDCurrentvsThroughput Figure44.AVDDCurrentvsTemperature(DuringSampling) 20 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TypicalCharacteristics(continued) atTA=25°
C,AVDD=5V,DVDD=3V,VREF=4.096V(internal),andmaximumthroughput(unlessotherwisenoted) 2.8 ±12.288V ±5.12V 0-10.24V ±10.24V ±2.56V 0-6.144V ±6.144V 0-12.288V 0-5.12V 2.7
3 ±12.288V ±5.12V 0-10.24V ±10.24V ±2.56V 0-6.144V 2.5 ±6.144V 0-12.288V 0-5.12V
2 IAVDDStandby(mA)IAVDDPD(uA) 2.6 1.5 12.5 0.5 2.4-40 -
7 26 59 92 Free-AirTemperature(0C) 125 D067
0 -40 -
7 26 59 92 125 Free-AirTemperature(0C)D068 Figure45.AVDDCurrentvsTemperature(StandbyMode) Figure46.AVDDCurrentvsTemperature(Power-DownMode) Copyright©2016,TexasInstrumentsIncorporated 21 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 7DetailedDescription 7.1Overview TheADS868xdevicesbelongtoafamilyofhigh-speed,high-performance,easy-to-useintegrateddataacquisitionsystem.Thissingle-channeldevicesupportstruebipolarinputvoltageswingsupto±12.288V,operatingonasingle5-Vanalogsupply.ThedevicefeaturesanenhancedSPIinterface(multiSPI)thatallowsthesamplingratetobemaximizedevenwithlowerspeedhostcontrollers. Thedeviceconsistsofahigh-precisionessiveapproximationregister(SAR)analog-to-digitalconverter(ADC)andapower-optimizedanalogfront-end(AFE)circuitforsignalconditioningthatincludes:•Ahigh-resistiveinputimpedance(≥1MΩ)thatisindependentofthesamplingrate•Aprogrammablegainamplifier(PGA)withapseudo-differentialinputconfigurationsupportingninesoftware- programmableunipolarandbipolarinputranges•Asecond-order,low-passantialiasingfilter•AnADCdriveramplifierthatensuresquicksettlingoftheSARADCinputforhighuracy•Aninputovervoltageprotectioncircuitupto±20V Thedevicealsofeaturesalowtemperaturedrift,4.096-Vinternalreferencewithafast-settlingbufferandamultiSPIserialinterfacewithdaisy-chain(DAISY)andALARMfeatures. TheintegrationofthemultichannelprecisionAFEcircuitwithhighinputimpedanceandaprecisionADCoperatingfromasingle5-Vsupplyoffersasimplifiedendsolutionwithoutrequiringexternalhigh-voltagebipolarsuppliesplicateddrivercircuits. 7.2FunctionalBlockDiagram AVDDADS868x DVDD 4.096-VReference REFIOREFCAP AIN_PAIN_GND 1M:1M: OVPOVP PGA AGND 2nd-OrderLPF ADCDriver VBIAS Oscillator 16-BitSARADC DigitalLogicandInterface CONVST/CSSCLKSDISDO DGND REFGNDCopyright©2016,TexasInstrumentsIncorporated 22 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 7.3FeatureDescription 7.3.1AnalogInputStructure Thedevicefeaturesapseudo-differentialinputstructure,meaningthatthesingle-endedanaloginputsignalisappliedatthepositiveinputAIN_PandthenegativeinputAIN_GNDistiedtoGND.Figure47showsthesimplifiedcircuitschematicfortheAFEcircuit,includingtheinputovervoltageprotectioncircuit,PGA,low-passfilter(LPF),andhigh-speedADCdriver. AIN_PAIN_GND 1M:OVP OVP1M: PGA 2nd-OrderLPF ADCDriver ADC CONVST/CSSCLKSDISDO VB Figure47.SimplifiedAnalogFront-EndCircuitSchematic Thedevicecansupportmultipleunipolarorbipolar,single-endedinputvoltagerangesbasedontheconfigurationoftheprogramregisters.AsexplainedintheRANGE_SEL_REGregister,theinputvoltagerangeforeachanalogchannelcanbeconfiguredtobipolar±3×VREF,±2.5×VREF,±1.5×VREF,±1.25×VREF,and±0.625×VREForunipolar0to3×VREF,0to2.5×VREF,0to1.5×VREFand0to1.25×VREF.Withtheinternalorexternalreferencevoltagesetto4.096V,theinputrangesofthedevicecanbeconfiguredtobipolarrangesof±12.288V,±10.24V,±6.144V,±5.12V,and±2.56Vorunipolarrangesof0Vto12.288V,0Vto10.24V,0Vto6.144V,and0Vto5.12V. Thedevicesamplesthevoltagedifference(AIN_P–AIN_GND)betweentheanaloginputandtheAIN_GNDpin.Thedeviceallowsa±0.1-VrangeontheAIN_GNDpin.Thisfeatureisusefulinmodularsystemswherethesensororsignal-conditioningblockisfurtherawayfromtheADContheboardandwhenadifferenceinthegroundpotentialofthesensororsignalconditionerfromtheADCgroundispossible.Insuchcases,runningseparatewiresfromtheAIN_GNDpinofthedevicetothesensororsignal-conditioninggroundismended.Inordertoobtainoptimumperformance,theinputcurrentsandimpedancesalongeachinputpatharemendedtobematched.Thetwosingle-endedsignalstoAIN_PandAIN_GNDmustberoutedassymmetricallyaspossiblefromthesignalsourcetotheADCinputpins. Iftheanaloginputpin(AIN_P)tothedeviceisleftfloating,theoutputoftheADCcorrespondstoaninternalbiasingvoltage.TheoutputfromtheADCmustbeconsideredasinvalidifthedeviceisoperatedwithfloatinginputpins.Thisconditiondoesnotcauseanydamagetothedevice,whichesfullyfunctionalwhenavalidinputvoltageisappliedtothepins. 7.3.2AnalogInputImpedance Thedevicepresentsaresistiveinputimpedance≥1MΩoneachoftheanaloginputs.TheinputimpedanceisindependentoftheADCsamplingfrequencyortheinputsignalfrequency.TheprimaryadvantageofsuchhighimpedanceinputsistheeaseofdrivingtheADCinputswithoutrequiringdrivingamplifierswithlowoutputimpedance.Bipolar,high-voltagepowersuppliesarenotrequiredinthesystembecausethisADCdoesnotrequireanyhigh-voltage,front-enddrivers.Inmostapplications,thesignalsourcesorsensoroutputscanbedirectlyconnectedtotheADCinput,thussignificantlysimplifyingthedesignofthesignalchain. Inordertomaintainthedcuracyofthesystem,matchingtheexternalsourceimpedanceontheAIN_PinputpinwithanequivalentresistanceontheAIN_GNDpinismended.Thismatchinghelpscancelanyadditionaloffseterrorcontributedbytheexternalresistance. Copyright©2016,TexasInstrumentsIncorporated 23 ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 FeatureDescription(continued) 7.3.3InputProtectionCircuit Thedevicefeaturesaninternalovervoltageprotection(OVP)circuitoneachoftheanaloginputs.Usetheinternalprotectioncircuitonlyasasecondaryprotectionscheme.Theexternalprotectiondevicesintheendapplicationarehighlymendedtobeusedtoprotectagainstsurges,electrostaticdischarge(ESD),andelectricalfasttransient(EFT)conditions.AconceptualblockdiagramoftheinternalOVPcircuitisshowninFigure48. AVDDVP+ RFB 0V ESD AVDD VP- RS AIN_
P RS AIN_GND 1MŸD1pD2p AVDDD1n V± V+ + 1MŸ D2n RDCESD VOUT VBGND Figure48.InputOvervoltageProtectionCircuitSchematic AsshowninFigure48,binationofthe1-MΩ(or,1.2MΩforappropriateinputranges)inputresistorsalongwiththePGAgain-settingresistorsRFBandRDClimitthecurrentflowingintotheinputpin.binationofanti-paralleldiodes,D1andD2areaddedtoprotecttheinternalcircuitryandsettheovervoltageprotectionlimits. Table1explainsthevariousoperatingconditionsforthedevicewhenpoweredon.Thistableindicatesthatwhenthedeviceisproperlypoweredup(AVDD=5V)oroffersalowimpedanceof<30kΩ,theinternalovervoltageprotectioncircuitcanwithstandupto±20Vontheanaloginputpins. Table1.InputOvervoltageProtectionLimitsWhenAVDD=5VorOffersaLowImpedanceof<30kΩ
(1) INPUTCONDITION(VOVP=±20V) CONDITION RANGE |VIN|<|VRANGE| Withinoperatingrange |VRANGE|<|VIN|<|VOVP| Beyondoperatingrangebutwithinovervoltagerange |VIN|>|VOVP| Beyondovervoltagerange TESTCONDITION Allinputranges Allinputranges Allinputranges ADCOUTPUT COMMENTS ValidSaturatedSaturated Devicefunctionsasperdatasheetspecifications. ADCoutputissaturated,butdeviceisinternallyprotected(notmendedforextendedtime).Thisusageconditioncancauseirreversibledamagetothedevice.
(1)GND=0V,AIN_GND=0V,|VRANGE|isthemaximuminputvoltageforanyselectedinputrange,and|VOVP|isthebreak-downvoltagefortheinternalOVPcircuit.AssumethatRSisapproximately0Ω. 24 Copyright©2016,TexasInstrumentsIncorporated ADS8681,ADS8685,ADS8689 ZHCSEV3B–FEBRUARY2016–REVISEDDECEMBER2016 TheresultsindicatedinTable1arebasedonanassumptionthattheanaloginputpinisdrivenbyaverylowimpedancesource(RSisapproximately0Ω).However,ifthesourcedrivingtheinputhashigherimpedance,thecurrentflowingthroughtheprotectiondiodesreducesfurther,therebyincreasingtheOVPvoltagerange.Notethathighersourceimpedancesresultingainerrorsandcontributetooverallsystemnoiseperformance. Figure49showsthevoltageversuscurrentresponseoftheinternalovervoltageprotectioncircuitwhenthedeviceispoweredon.ordingtothiscurrent-to-voltage(I-V)response,thecurrentflowingintothedeviceinputpinislimitedbythe1-MΩ(or1.2MΩforappropriateinputranges)inputimpedance.However,forvoltagesbeyond±20V,theinternalnodevoltagessurpassthebreak-downvoltageforinternaltransistors,thussettingthelimitforovervoltageprotectionontheinputpin. ThesameovervoltageprotectioncircuitalsoprovidesprotectiontothedevicewhenthedeviceisnotpoweredonandAVDDisfloatingwithanimpedance>30kΩ.ThisconditioncanarisewhentheinputsignalsareappliedbeforetheADCisfullypoweredon.TheovervoltageprotectionlimitsforthisconditionareshowninTable2. Table2.InputOvervoltageProtectionLimitsWhenAVDD=FloatingwithImpedance>30kΩ
(1) CONDITION INPUTCONDITION(VOVP=±11V) RANGE |VIN|<|VOVP| Withinovervoltagerange |VIN|>|VOVP| Beyondovervoltagerange TESTCONDITION Allinputranges Allinputranges ADCOUTPUT COMMENTS InvalidInvalid DeviceisnotfunctionalbutisprotectedinternallybytheOVPcircuit. Thisusageconditioncancauseirreversibledamagetothedevice.
(1)AVDD=floating,GND=0V,AIN_GND=0V,|VRANGE|isthemaximuminputvoltageforanyselectedinputrange,and|VOVP|isthebreak-downvoltagefortheinternalOVPcircuit.AssumethatRSisapproximately0Ω. Figure50showstheI-Vresponseoftheinternalovervoltageprotectioncircuitwhenthedeviceisnotpoweredon.ordingtothisI-Vresp
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