产品锤子10位高管退出

ADS7251,ADS7851ZHCSCB7A–JANUARY2014–REVISEDAPRIL2014ADS7x5112位位,,2MSPS和和14位位,,1.
5MSPS,,双双路路,,差差分分输输入入,,同同步步采采样样模模数数转转换换器器,,具具有有内内部部基基准准1特特性性3说说明明112和14位引脚兼容系列ADS7251和ADS7851属于引脚兼容、双路、高速、同步采样模数转换器(ADC)产品系列,此系列产品支两个通道同时采样持全差分模拟输入,并且特有2个单独的内部电压基支持全差分模拟输入准.
ADS7251提供12位分辨率以及高达2MSPS的独立内部基准(每个ADC一个)采样速度.
ADS7851提供14位分辨率以及高达高速:1.
5MSPS的采样速度.
–使用ADS7251(12位)时高达2MSPS–使用ADS7851(14位)时高达1.
5MSPS此器件支持宽数字电源电压范围,从而通过一个简单串出色的性能:口轻松实现与多种数字主机控制器的通信.
两个器件–ADS7251:都在扩展工业用温度范围(-40°C至+125°C)内完全–信噪比(SNR):73dB额定运行,并且采用引脚兼容、节省空间的WQFN-16–积分非线性(INL):±1最低有效位(LSB)(3mmx3mm)封装.
–ADS7851:器器件件信信息息–信噪比(SNR):83.
5dB订订货货编编号号封封装装封封装装尺尺寸寸–积分非线性(INL):±2LSBADS7251RTEWQFN(16)3mmx3mm在-40°C至+125°C的扩展工业用温度范围内完全ADS7851RTEWQFN(16)3mmx3mm额定运行小型封装:超薄四方扁平无引线(WQFN)-16(3mm典典型型应应用用图图x3mm)2应应用用范范围围电机控制:与SinCos编码器的直接对接光网络互连:掺铒光纤放大器(EDFA)增益控制环路保护中继器电源质量测量三相电源控制可编程逻辑控制器工业自动化1PRODUCTIONDATAinformationiscurrentasofpublicationdate.
ProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.
Productionprocessingdoesnotnecessarilyincludetestingofallparameters.
EnglishDataSheet:SBAS587ADS7251,ADS7851ZHCSCB7A–JANUARY2014–REVISEDAPRIL2014www.
ti.
com.
cn目目录录7.
1Overview171特特性性.
17.
2FunctionalBlockDiagram172应应用用范范围围.
17.
3FeatureDescription.
183说说明明.
17.
4DeviceFunctionalModes.
214修修订订历历史史记记录录28ApplicationandImplementation235TerminalConfigurationandFunctions.
38.
1ApplicationInformation.
236Specifications.
48.
2TypicalApplication236.
1AbsoluteMaximumRatings49PowerSupplyRecommendations.
276.
2HandlingRatings.
410Layout.
286.
3RecommendedOperatingConditions.
410.
1LayoutGuidelines286.
4ThermalInformation.
410.
2LayoutExample286.
5ElectricalCharacteristics:ADS7251511器器件件和和文文档档支支持持296.
6ElectricalCharacteristics:ADS7851611.
1文档支持.
296.
7ElectricalCharacteristics:Common711.
2相关链接.
296.
8ADS7251TimingCharacteristics811.
3Trademarks.
296.
9ADS7851TimingCharacteristics911.
4ElectrostaticDischargeCaution.
296.
10TypicalCharacteristics:ADS72511011.
5Glossary.
296.
11TypicalCharacteristics:ADS78511312机机械械封封装装和和可可订订购购信信息息296.
12TypicalCharacteristics:Common167DetailedDescription174修修订订历历史史记记录录ChangesfromOriginal(January2014)toRevisionAPage已将格式更改为最新的数据表标准;已添加电路板布局部分,已移动现有部分1DeletedOrderingInformationtable3ChangedSupplyCurrent,IDVDDparametertypicalspecificationinElectricalCharacteristics:ADS7251table.
5ChangedSupplyCurrent,IDVDDparametertypicalspecificationinElectricalCharacteristics:ADS7851table.
6ChangedInputVoltagecolumninTable1202版权2014,TexasInstrumentsIncorporatedADS7251,ADS7851www.
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com.
cnZHCSCB7A–JANUARY2014–REVISEDAPRIL20145TerminalConfigurationandFunctionsRTEPackageWQFN-16(TopView)TerminalDescriptionsTERMINALNAMENO.
I/ODESCRIPTIONAINM-A16AnaloginputNegativeanaloginput,channelAAINP-A15AnaloginputPositiveanaloginput,channelAAINM-B5AnaloginputNegativeanaloginput,channelBAINP-B6AnaloginputPositiveanaloginput,channelBAVDD14SupplyADCsupplyvoltageCS9DigitalinputChip-selectsignal;activelowDVDD7SupplyDigitalI/OsupplyGND8,13SupplyDigitalgroundREFGND-A2SupplyReferencegroundpotential,channelAREFGND-B3SupplyReferencegroundpotential,channelBREFOUT-A1AnalogoutputReferencevoltageoutput,REF_AREFOUT-B4AnalogoutputReferencevoltageoutput,REF_BSCLK10DigitalinputSerialcommunicationclockSDO-A11DigitaloutputDataoutputforserialcommunication,channelASDO-B12DigitaloutputDataoutputforserialcommunication,channelBExposedthermalpad.
ThermalpadSupplyTIrecommendsconnectingthispintotheprintedcircuitboard(PCB)ground.
Copyright2014,TexasInstrumentsIncorporated3ADS7251,ADS7851ZHCSCB7A–JANUARY2014–REVISEDAPRIL2014www.
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cn6Specifications6.
1AbsoluteMaximumRatings(1)overoperatingfree-airtemperaturerange(unlessotherwisenoted)MINMAXUNITAVDDtoGND–0.
3+7VSupplyvoltageDVDDtoGND–0.
3+7VAINP_xtoREFGND_xREFGND_x–0.
3AVDD+0.
3VAnaloginputvoltageAINM_xtoREFGND_xREFGND_x–0.
3AVDD+0.
3VDigitalinputvoltageCS,SCLKtoGNDGND–0.
3DVDD+0.
3VGroundvoltagedifference|REFGND_x–GND|0.
3VInputcurrentAnypinexceptsupplypins±10mAMaximumvirtualjunctiontemperature,TJ+150°C(1)StressesbeyondthoselistedunderAbsoluteMaximumRatingsmaycausepermanentdamagetothedevice.
Thesearestressratingsonly,whichdonotimplyfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedunderRecommendedOperatingConditions.
Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability.
6.
2HandlingRatingsMINMAXUNITTstgStoragetemperaturerange–65+150°CHumanbodymodel(HBM)ESDstressvoltage(2),±2000VJEDECstandard22,testmethodA114-C.
01VESD(1),allpinsChargeddevicemodel(CDM)ESDstressvoltage(3),±500VJEDECstandard22,testmethodC101(1)Electrostaticdischarge(ESD)tomeasuredevicesensitivityandimmunitytodamagecausedbyassemblylineelectrostaticdischargesintothedevice.
(2)LevellistedaboveisthepassinglevelperANSI,ESDA,andJEDECJS-001.
JEDECdocumentJEP155statesthat±2000-VHBMallowssafemanufacturingwithastandardESDcontrolprocess.
(3)LevellistedaboveisthepassinglevelperEIA-JEDECJESD22-C101.
JEDECdocumentJEP157statesthat±500-VCDMallowssafemanufacturingwithastandardESDcontrolprocess.
6.
3RecommendedOperatingConditionsoveroperatingfree-airtemperaturerange(unlessotherwisenoted)MINNOMMAXUNITAVDDAnalogsupplyvoltage5VDVDDDigitalsupplyvoltage3.
3V6.
4ThermalInformationADS7251,ADS7851THERMALMETRIC(1)UNITRTE(WQFN)16TERMINALSRθJAJunction-to-ambientthermalresistance33.
3RθJC(top)Junction-to-case(top)thermalresistance29.
5RθJBJunction-to-boardthermalresistance7.
3°C/WψJTJunction-to-topcharacterizationparameter0.
2ψJBJunction-to-boardcharacterizationparameter7.
4RθJC(bot)Junction-to-case(bottom)thermalresistance0.
9(1)Formoreinformationabouttraditionalandnewthermalmetrics,seetheICPackageThermalMetricsapplicationreport,SPRA953.
4Copyright2014,TexasInstrumentsIncorporatedADS7251,ADS7851www.
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com.
cnZHCSCB7A–JANUARY2014–REVISEDAPRIL20146.
5ElectricalCharacteristics:ADS7251AllminimumandmaximumspecificationsareatTA=–40°Cto+125°C,AVDD=5V,VREF_A=VREF_B=2.
5V,andfDATA=2MSPS,unlessotherwisenoted.
TypicalvaluesareatTA=+25°C,AVDD=5V,andDVDD=3.
3V.
PARAMETERTESTCONDITIONSMINTYPMAXUNITRESOLUTIONResolution12BitsSAMPLINGDYNAMICStCONVConversiontimetSU_CSCK+12tCLKnstACQAcquisitiontime75nsfDATADatarate2MSPSfCLKClockfrequency32MHzDCACCURACYNMCNomissingcodes12BitsDNLDifferentialnonlinearity–0.
99±0.
31LSBINLIntegralnonlinearity–1±0.
51LSBVOSInputoffseterror–1±0.
21mVVOSmatchADC_AtoADC_B–1±0.
21mVdVOS/dTInputoffsetthermaldrift4μV/°CReferencedtothevoltageatGEGainerror–0.
1%±0.
05%0.
1%REFOUT_xGERRmatchADC_AtoADC_B–0.
1%±0.
05%0.
1%ReferencedtothevoltageatGE/dTGainerrorthermaldrift1ppm/°CREFOUT_xCMRRCommon-moderejectionratioBothADCs,dcto20kHz72dBACACCURACYSINADSignal-to-noise+distortion72.
772.
9dBSNRSignal-to-noiseratio72.
873dBFor20-kHzinputfrequency,at–0.
5dBFSTHDTotalharmonicdistortion–90dBSFDRSpurious-freedynamicrange90dBIsolationbetweenADC_AandfIN=15kHz,fNOISE=25kHz–105dBADC_BSUPPLYCURRENTAnalog,duringThroughput=2MSPS,IAVDD-DYNAMIC1112mAconversionAVDD=5VSupplyIAVDD-STATICcurrentAnalog,static5.
5mAIDVDDDigital,forcode8000.
15mAPOWERDISSIPATIONThroughput=2MSPS,PD-ACTIVEDuringconversion5560mWPowerAVDD=5VdissipationPD-STATICStaticmode27.
5mWCopyright2014,TexasInstrumentsIncorporated5ADS7251,ADS7851ZHCSCB7A–JANUARY2014–REVISEDAPRIL2014www.
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cn6.
6ElectricalCharacteristics:ADS7851AllminimumandmaximumspecificationsareatTA=–40°Cto+125°C,AVDD=5V,VREF_A=VREF_B=2.
5V,andfDATA=1.
5MSPS,unlessotherwisenoted.
TypicalvaluesareatTA=+25°C,AVDD=5V,andDVDD=3.
3V.
PARAMETERTESTCONDITIONSMINTYPMAXUNITRESOLUTIONResolution14BitsSAMPLINGDYNAMICStCONVConversiontimetSU_CSCK+14tCLKnstACQAcquisitiontime90nsfDATADatarate1500kSPSfCLKClockfrequency27MHzDCACCURACYNMCNomissingcodes13BitsDNLDifferentialnonlinearity–1±0.
752LSBINLIntegralnonlinearity–2±12LSBVOSInputoffseterror–1±0.
21mVVOSmatchADC_AtoADC_B–1±0.
21mVdVOS/dTInputoffsetthermaldrift1μV/°CReferencedtothevoltageatGEGainerror–0.
1%±0.
05%0.
1%REFOUT_xGERRmatchADC_AtoADC_B–0.
1%±0.
05%0.
1%ReferencedtothevoltageatGE/dTGainerrorthermaldrift1ppm/°CREFOUT_xCMRRCommon-moderejectionratioBothADCs,dcto20kHz72dBACACCURACYSINADSignal-to-noise+distortion81.
482.
6dBSNRSignal-to-noiseratio8283.
5dBFor20-kHzinputfrequency,at–0.
5dBFSTHDTotalharmonicdistortion–90dBSFDRSpurious-freedynamicrange90dBIsolationbetweenADC_AandfIN=15kHz,fNOISE=25kHz–120dBADC_BSUPPLYCURRENTAnalog,duringThroughput=1.
5MSPS,IAVDD-DYNAMIC1012mAconversionAVDD=5VSupplyIAVDD-STATICAnalog,static5.
5mAcurrentDigital,forcodeIDVDD0.
15mA2000POWERDISSIPATIONThroughput=1.
5MSPS,PD-ACTIVEDuringconversion5060mWPowerAVDD=5VdissipationPD-STATICStaticmode27.
5mW6Copyright2014,TexasInstrumentsIncorporatedADS7251,ADS7851www.
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com.
cnZHCSCB7A–JANUARY2014–REVISEDAPRIL20146.
7ElectricalCharacteristics:CommonAllminimumandmaximumspecificationsareatTA=–40°Cto+125°C,AVDD=5V,VREF_A=VREF_B=2.
5V,andfDATA=2MSPS,unlessotherwisenoted.
TypicalvaluesareatTA=+25°C,AVDD=5V,andDVDD=3.
3V.
PARAMETERTESTCONDITIONSMINTYPMAXUNITANALOGINPUTForAVDD≥5V–2VREF2VREFVFull-scaleinputrangeFSR(AINP_x–AINM_x)ForAVDD2*VREF–1LSBPFSC7FF1FFFFigure40.
IdealTransferCharacteristics20Copyright2014,TexasInstrumentsIncorporatedADS7251,ADS7851www.
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com.
cnZHCSCB7A–JANUARY2014–REVISEDAPRIL20147.
4DeviceFunctionalModes7.
4.
1SerialInterfaceThedevicessupportasimple,SPI-compatibleinterfacetotheexternaldigitalhost.
TheCSsignaldefinesoneconversionandserialtransferframe.
AframestartswithaCSfallingedgeandendswithaCSrisingedge.
TheSDO_AandSDO_BpinsoutputtheADC_AandADC_Bconversionresults,respectively.
Figure41showsadetailedtimingdiagramfortheADS7251.
Figure41.
ADS7251SerialInterfaceTimingDiagramFigure42showsadetailedtimingdiagramfortheADS7851.
Figure42.
ADS7851SerialInterfaceTimingDiagramCopyright2014,TexasInstrumentsIncorporated21ADS7251,ADS7851ZHCSCB7A–JANUARY2014–REVISEDAPRIL2014www.
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cnDeviceFunctionalModes(continued)ACSfallingedgebringstheserialdatabusoutof3-stateandalsooutputs'0'ontheSDO_AandSDO_Bpins.
AminimumdelayoftSU_CSCKmustelapsebetweentheCSfallingedgeandthefirstSCLKfallingedge.
Thesubsequentclockedgesareusedtoshiftouttheconversionresultusingtheserialinterface,asshowninTable2.
Thesample-and-holdcircuitreturnstosamplemodeassoonastheconversionprocessisover.
Anyextraclockedgesoutputa'0'ontheSDOpins.
ACSrisingedgeendstheframeandbringstheserialdatabusto3-state.
Table2.
DataLaunchEdgeLAUNCHEDGESCLKCS↑DEVICEPINCS↓↓1↓2…↓13↓14↓15↓16…SDO-A00D13_A…D2_AD1_AD0_A0…Hi-ZADS7851SDO-B00D13_B…D2_BD1_BD0_B0…Hi-ZSDO-A00D11_A…D0_A000…Hi-ZADS7251SDO-B00D11_B…D0_B000…Hi-Z7.
4.
2Short-CyclingFeatureFortheADS7851,aminimumof16SCLKrisingedgesmustbeprovidedbetweenthebeginningandendoftheframetocompletethe14-bitdatatransfer.
FortheADS7251,aminimumof14SCLKrisingedgesmustbeprovidedbetweenthebeginningandendoftheframetocompletethe12-bitdatatransfer.
AsshowninFigure43,ifCSisbroughthighbeforetheexpectednumberofSCLKrisingedgesareprovided,thecurrentframeisabortedandthedevicestartssamplingthenewanaloginputsignal.
However,theoutputdatabitslatchedintothedigitalhostbeforethisCSrisingedgearestillvaliddatacorrespondingtosampleN.
Afterabortingthecurrentframe,CSmustbekepthighfortACQtoensureminimumacquisitiontimeisprovidedforthenextconversion.
Figure43.
Short-CyclingFeature22Copyright2014,TexasInstrumentsIncorporatedADS7251,ADS7851www.
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com.
cnZHCSCB7A–JANUARY2014–REVISEDAPRIL20148ApplicationandImplementation8.
1ApplicationInformationThetwoprimarycircuitsrequiredtomaximizetheperformanceofahigh-precision,successiveapproximationregister(SAR),analog-to-digitalconverter(ADC)aretheinputdriverandthereferencedrivercircuits.
TheADS7851andADS7251featureaninternalreferencedesignedtosupportdevicerequirements.
Thissectiondetailssomegeneralprinciplesfordesigningtheinputdrivercircuitandprovidessomeapplicationcircuitsdesignedusingthesedevices.
8.
2TypicalApplicationTheapplicationcircuitshowninFigure44isoptimizedforusingtheADS7251ata2-MSPSthroughputtoachievelowestdistortionandlowestnoiseforinputsignalfrequenciesupto100kHz.
Figure44.
ADS7251DAQCircuit:MaximumSINADforInputSignalFrequenciesupto100kHzTheapplicationcircuitshowninFigure45isoptimizedforusingtheADS7851ata1.
5-MSPSthroughputtoachievelowestdistortionandlowestnoiseforinputsignalfrequenciesupto100kHz.
Figure45.
ADS7851DAQCircuit:MaximumSINADforInputSignalFrequenciesupto100kHzCopyright2014,TexasInstrumentsIncorporated23ADS7251,ADS7851ZHCSCB7A–JANUARY2014–REVISEDAPRIL2014www.
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cnTypicalApplication(continued)8.
2.
1DesignRequirementsFortheADS7251,designaninputdriverandreferencedrivercircuittoachieve>71-dBSNRand81-dBSNRand<–90-dBTHDatinputfrequenciesof10kHzand100kHz.
8.
2.
2DetailedDesignProcedureTheinputdrivercircuitforahigh-precisionADCmainlyconsistsoftwoparts:adrivingamplifierandanantialiasingfilter.
Carefuldesignofthefront-endcircuitiscriticaltomeetthelinearityandnoiseperformanceofahigh-precisionADC.
8.
2.
2.
1InputAmplifierSelectionSelectioncriteriafortheinputamplifiersishighlydependentontheinputsignaltypeandtheperformancegoalsofthedataacquisitionsystem.
SomekeyamplifierspecificationstoconsiderwhileselectinganappropriateamplifiertodrivetheinputsoftheADCare:Small-signalbandwidth.
Selectthesmall-signalbandwidthoftheinputamplifierstobeashighaspossibleaftermeetingthepowerbudgetofthesystem.
Higherbandwidthreducestheclosed-loopoutputimpedanceoftheamplifier,thusallowingtheamplifiertomoreeasilydrivethelowcutofffrequencyRCfilterattheADCinputs.
Higherbandwidthalsominimizestheharmonicdistortionathigherinputfrequencies.
Inordertomaintaintheoverallstabilityoftheinputdrivercircuit,theamplifierbandwidthshouldbeselectedasdescribedinEquation9:(9)Noise.
Noisecontributionofthefront-endamplifiersshouldbeaslowaspossibletopreventanydegradationinSNRperformanceofthesystem.
Asaruleofthumb,toensurethatthenoiseperformanceofthedataacquisitionsystemisnotlimitedbythefront-endcircuit,thetotalnoisecontributionfromthefront-endcircuitshouldbekeptbelow20%oftheinput-referrednoiseoftheADC.
NoisefromtheinputdrivercircuitisbandlimitedbydesigningalowcutofffrequencyRCfilter,asexplainedinEquation10.
where:V1/f_AMP_PPisthepeak-to-peakflickernoiseinVRMS,en_RMSistheamplifierbroadbandnoisedensityinnV/√Hz,f–3dBisthe3-dBbandwidthoftheRCfilter,andNGisthenoisegainofthefront-endcircuit,whichisequalto'1'inabufferconfiguration.
(10)Distortion.
BoththeADCandtheinputdriverintroducenonlinearityinadataacquisitionblock.
Asaruleofthumb,toensurethatthedistortionperformanceofthedataacquisitionsystemisnotlimitedbythefront-endcircuit,thedistortionoftheinputdrivershouldbeatleast10dBlowerthanthedistortionoftheADC,asshowninEquation11.
(11)SettlingTime.
Fordcsignalswithfasttransientsthatarecommoninamultiplexedapplication,theinputsignalmustsettletothedesiredaccuracyattheinputsoftheADCduringtheacquisitiontimewindow.
ThisconditioniscriticaltomaintaintheoveralllinearityperformanceoftheADC.
Typically,theamplifierdatasheetsspecifytheoutputsettlingperformanceonlyupto0.
1%to0.
001%,whichmaynotbesufficientforthedesiredaccuracy.
Therefore,thesettlingbehavioroftheinputdrivershouldalwaysbeverifiedbyTINA-SPICEsimulationsbeforeselectingtheamplifier.
24Copyright2014,TexasInstrumentsIncorporatedADS7251,ADS7851www.
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cnZHCSCB7A–JANUARY2014–REVISEDAPRIL2014TypicalApplication(continued)Thedistortionresultingfromvariationinthecommon-modesignaliseliminatedbyusingafully-differentialamplifier(FDA)inaninvertinggainconfigurationthatestablishesafixedcommon-modelevelattheADCinput.
Thisconfigurationalsoeliminatestherequirementofrail-to-railswingattheamplifierinput.
Thelow-powerTHS4521,usedasaninputdriver,providesexceptionalacperformancebecauseofitsextremelylow-distortionandhigh-bandwidthspecifications.
ThedeviceREFOUT_xpincanbedirectlyconnectedtotheVOCMpinoftheTHS4521tosettheoutputcommon-modevoltageto2.
5V,asrequiredbytheADC.
8.
2.
2.
2AntialiasingFilterConvertinganalog-to-digitalsignalsrequiressamplinganinputsignalataconstantrate.
Anyhigherfrequencycontentintheinputsignalbeyondhalfthesamplingfrequencyisdigitizedandfoldedbackintothelow-frequencyspectrum.
Thisprocessiscalledaliasing.
Therefore,ananalog,antialiasingfiltermustbeusedtoremovetheharmoniccontentfromtheinputsignalbeforebeingsampledbytheADC.
Anantialiasingfilterisdesignedasalow-pass,RCfilter,forwhichthe3-dBbandwidthisoptimizedbasedonspecificapplicationrequirements(asshowninFigure46).
Fordcsignalswithfasttransients(includingmultiplexedinputsignals),ahigh-bandwidthfilterisdesignedtoallowaccuratelysettlingthesignalattheADCinputsduringthesmallacquisitiontimewindow.
Foracsignals,thefilterbandwidthshouldbekeptlowtoband-limitthenoisefedintotheADCinput,therebyincreasingthesignal-to-noiseratio(SNR)ofthesystem.
Besidesfilteringthenoisefromthefront-enddrivecircuitry,theRCfilteralsohelpsattenuatethesamplingchargeinjectionfromtheswitched-capacitorinputstageoftheADC.
Afiltercapacitor,CFLT,isconnectedacrosstheADCinputs.
Thiscapacitorhelpsreducethesamplingchargeinjectionandprovidesachargebuckettoquicklychargetheinternalsample-and-holdcapacitorsduringtheacquisitionprocess.
Asaruleofthumb,thevalueofthiscapacitorshouldbeatleast10timesthespecifiedvalueoftheADCsamplingcapacitance.
Forthesedevices,theinputsamplingcapacitanceisequalto40pF.
Thus,thevalueofCFLTshouldbegreaterthan400pF.
ThecapacitorshouldbeaCOG-orNPO-typebecausethesecapacitortypeshaveahigh-Q,low-temperaturecoefficient,andstableelectricalcharacteristicsundervaryingvoltages,frequency,andtime.
Notethatdrivingcapacitiveloadscandegradethephasemarginoftheinputamplifiers,thusmakingtheamplifiermarginallyunstable.
Toavoidamplifierstabilityissues,seriesisolationresistors(RFLT)areusedattheoutputoftheamplifiers.
AhighervalueofRFLTishelpfulfromtheamplifierstabilityperspective,butaddsdistortionasaresultofinteractionswiththenonlinearinputimpedanceoftheADC.
Distortionincreaseswithsourceimpedance,inputsignalfrequency,andinputsignalamplitude.
Therefore,theselectionofRFLTrequiresbalancingthestabilityanddistortionofthedesign.
Forthesedevices,TIrecommendslimitingthevalueofRFLTtoamaximumof22Ωinordertoavoidanysignificantdegradationinlinearityperformance.
Thetoleranceoftheselectedresistorscanbechosenas1%becausetheuseofadifferentialcapacitorattheinputbalancestheeffectsresultingfromanyresistormismatch.
Figure46.
AntialiasingFilterTheinputamplifierbandwidthshouldbemuchhigherthanthecutofffrequencyoftheantialiasingfilter.
TIstronglyrecommendsperformingaSPICEsimulationtoconfirmthattheamplifierhasmorethan40°phasemarginwiththeselectedfilter.
Simulationiscriticalbecauseevenwithhigh-bandwidthamplifiers,someamplifiersmightrequiremorebandwidththanotherstodrivesimilarfilters.
Ifanamplifierhaslessthana40°phasemarginwith22-Ωresistors,usingadifferentamplifierwithhigherbandwidthorreducingthefiltercutofffrequencywithalargerdifferentialcapacitorisadvisable.
Inaddition,thecomponentsoftheantialiasingfilteraresuchthatthenoisefromthefront-endcircuitiskeptlowwithoutaddingdistortiontotheinputsignal.
Copyright2014,TexasInstrumentsIncorporated25ADS7251,ADS7851ZHCSCB7A–JANUARY2014–REVISEDAPRIL2014www.
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cnTypicalApplication(continued)8.
2.
3ApplicationCurvesFigure47showsanFFTplotfortheADS7251withthecircuitshowninFigure44andaninputfrequencyof10kHz.
Figure48showsanFFTplotfortheADS7251withthesamecircuitconfigurationbutforaninputfrequencyof100kHz.
Figure47.
TestResultsforADS7251witha10-kHzInputFigure48.
TestResultsforADS7251witha100-kHzInputFigure49showsanFFTplotfortheADS7851withthecircuitshowninFigure45andaninputfrequencyof10kHz.
Figure50showsanFFTplotfortheADS7251withthesamecircuitconfigurationbutforaninputfrequencyof100kHz.
Figure49.
TestResultswitha10-kHzInputFigure50.
TestResultswitha100-kHzInput26Copyright2014,TexasInstrumentsIncorporatedADS7251,ADS7851www.
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cnZHCSCB7A–JANUARY2014–REVISEDAPRIL20149PowerSupplyRecommendationsThedeviceshavetwoseparatepowersupplies:AVDDandDVDD.
ThedeviceoperatesonAVDD;DVDDisusedfortheinterfacecircuits.
AVDDandDVDDcanbeindependentlysettoanyvaluewithinthepermissibleranges.
TheAVDDsupplyvoltagevaluedefinesthepermissiblevoltageswingontheanaloginputpins.
Toavoidsaturationofoutputcodes,andtousethefulldynamicrangeontheanaloginputpins,AVDDmustbesetasshowninEquation12,Equation13,andEquation14:AVDD≥2*VREF_A(12)AVDD≥2*VREF_B(13)4.
75V≤AVDD≤5.
25V(14)DecoupletheAVDDandDVDDpinswiththeGNDpinusingindividual10-Fdecouplingcapacitors,asshowninFigure51.
Figure51.
Power-SupplyDecouplingCopyright2014,TexasInstrumentsIncorporated27ADS7251,ADS7851ZHCSCB7A–JANUARY2014–REVISEDAPRIL2014www.
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cn10Layout10.
1LayoutGuidelinesFigure52showsaboardlayoutexamplefortheADS7251andADS7851.
UseagroundplaneunderneaththedeviceandpartitionthePCBintoanaloganddigitalsections.
Avoidcrossingdigitallineswiththeanalogsignalpathandkeeptheanaloginputsignalsandthereferenceinputsignalsawayfromnoisesources.
AsshowninFigure52,theanaloginputandreferencesignalsareroutedontheleftsideoftheboardandthedigitalconnectionsareroutedontherightsideofthedevice.
Thepowersourcestothedevicemustbecleanandwell-bypassed.
Use10-μF,ceramicbypasscapacitorsincloseproximitytotheanalog(AVDD)anddigital(DVDD)power-supplypins.
AvoidplacingviasbetweentheAVDDandDVDDpinsandthebypasscapacitors.
Connectallgroundpinstothegroundplaneusingshort,low-impedancepaths.
TheREFOUT-AandREFOUT-Breferenceoutputsarebypassedwith10-μF,X7R-gradeceramiccapacitors(CREF-x).
PlacethereferencebypasscapacitorsascloseaspossibletothereferenceREFOUT-xpinsandconnectthebypasscapacitorsusingshort,low-inductanceconnections.
AvoidplacingviasbetweentheREFOUT-xpinsandthebypasscapacitors.
Small0.
1-Ωto0.
2-Ωresistors(RREF-x)areusedinserieswiththereferencebypasscapacitorstoimprovestability.
Thefly-wheelRCfiltersareplacedimmediatelynexttotheinputpins.
Amongceramicsurface-mountcapacitors,COG(NPO)ceramiccapacitorsprovidethebestcapacitanceprecision.
ThetypeofdielectricusedinCOG(NPO)ceramiccapacitorsprovidesthemoststableelectricalpropertiesovervoltage,frequency,andtemperaturechanges.
Figure52showsCIN-AandCIN-Bfiltercapacitorsplacedacrosstheanaloginputpinsofthedevice.
10.
2LayoutExampleFigure52.
ExampleLayoutfortheADS7251andADS785128Copyright2014,TexasInstrumentsIncorporatedADS7251,ADS7851www.
ti.
com.
cnZHCSCB7A–JANUARY2014–REVISEDAPRIL201411器器件件和和文文档档支支持持11.
1文文档档支支持持11.
1.
1相相关关文文档档相关文档如下:THS4521数据表,SBOS45811.
2相相关关链链接接以下表格列出了快速访问链接.
范围包括技术文档、支持与社区资源、工具和软件,以及样片与购买的快速访问.
Table3.
相相关关链链接接部部件件产产品品文文件件夹夹样样片片与与购购买买技技术术文文档档工工具具与与软软件件支支持持与与社社区区ADS7251请单击此处请单击此处请单击此处请单击此处请单击此处ADS7851请单击此处请单击此处请单击此处请单击此处请单击此处11.
3TrademarksTINAisatrademarkofTexasInstrumentsInc.
.
Allothertrademarksarethepropertyoftheirrespectiveowners.
11.
4ElectrostaticDischargeCautionThesedeviceshavelimitedbuilt-inESDprotection.
TheleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoamduringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.
11.
5GlossarySLYZ022—TIGlossary.
Thisglossarylistsandexplainsterms,acronymsanddefinitions.
12机机械械封封装装和和可可订订购购信信息息以下页中包括机械封装和可订购信息.
这些信息是针对指定器件可提供的最新数据.
这些数据会在无通知且不对本文档进行修订的情况下发生改变.
欲获得该数据表的浏览器版本,请查阅左侧的导航栏.
Copyright2014,TexasInstrumentsIncorporated29重重要要声声明明德州仪器(TI)及其下属子公司有权根据JESD46最新标准,对所提供的产品和服务进行更正、修改、增强、改进或其它更改,并有权根据JESD48最新标准中止提供任何产品和服务.
客户在下订单前应获取最新的相关信息,并验证这些信息是否完整且是最新的.
所有产品的销售都遵循在订单确认时所提供的TI销售条款与条件.
TI保证其所销售的组件的性能符合产品销售时TI半导体产品销售条件与条款的适用规范.
仅在TI保证的范围内,且TI认为有必要时才会使用测试或其它质量控制技术.
除非适用法律做出了硬性规定,否则没有必要对每种组件的所有参数进行测试.
TI对应用帮助或客户产品设计不承担任何义务.
客户应对其使用TI组件的产品和应用自行负责.
为尽量减小与客户产品和应用相关的风险,客户应提供充分的设计与操作安全措施.
TI不对任何TI专利权、版权、屏蔽作品权或其它与使用了TI组件或服务的组合设备、机器或流程相关的TI知识产权中授予的直接或隐含权限作出任何保证或解释.
TI所发布的与第三方产品或服务有关的信息,不能构成从TI获得使用这些产品或服务的许可、授权、或认可.
使用此类信息可能需要获得第三方的专利权或其它知识产权方面的许可,或是TI的专利权或其它知识产权方面的许可.
对于TI的产品手册或数据表中TI信息的重要部分,仅在没有对内容进行任何篡改且带有相关授权、条件、限制和声明的情况下才允许进行复制.
TI对此类篡改过的文件不承担任何责任或义务.
复制第三方的信息可能需要服从额外的限制条件.
在转售TI组件或服务时,如果对该组件或服务参数的陈述与TI标明的参数相比存在差异或虚假成分,则会失去相关TI组件或服务的所有明示或暗示授权,且这是不正当的、欺诈性商业行为.
TI对任何此类虚假陈述均不承担任何责任或义务.
客户认可并同意,尽管任何应用相关信息或支持仍可能由TI提供,但他们将独力负责满足与其产品及在其应用中使用TI产品相关的所有法律、法规和安全相关要求.
客户声明并同意,他们具备制定与实施安全措施所需的全部专业技术和知识,可预见故障的危险后果、监测故障及其后果、降低有可能造成人身伤害的故障的发生机率并采取适当的补救措施.
客户将全额赔偿因在此类安全关键应用中使用任何TI组件而对TI及其代理造成的任何损失.
在某些场合中,为了推进安全相关应用有可能对TI组件进行特别的促销.
TI的目标是利用此类组件帮助客户设计和创立其特有的可满足适用的功能安全性标准和要求的终端产品解决方案.
尽管如此,此类组件仍然服从这些条款.
TI组件未获得用于FDAClassIII(或类似的生命攸关医疗设备)的授权许可,除非各方授权官员已经达成了专门管控此类使用的特别协议.
只有那些TI特别注明属于军用等级或"增强型塑料"的TI组件才是设计或专门用于军事/航空应用或环境的.
购买者认可并同意,对并非指定面向军事或航空航天用途的TI组件进行军事或航空航天方面的应用,其风险由客户单独承担,并且由客户独力负责满足与此类使用相关的所有法律和法规要求.
TI已明确指定符合ISO/TS16949要求的产品,这些产品主要用于汽车.
在任何情况下,因使用非指定产品而无法达到ISO/TS16949要求,TI不承担任何责任.
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comIMPORTANTNOTICE邮寄地址:上海市浦东新区世纪大道1568号,中建大厦32楼邮政编码:200122Copyright2014,德州仪器半导体技术(上海)有限公司PACKAGEOPTIONADDENDUMwww.
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com24-Jul-2014Addendum-Page1PACKAGINGINFORMATIONOrderableDeviceStatus(1)PackageTypePackageDrawingPinsPackageQtyEcoPlan(2)Lead/BallFinish(6)MSLPeakTemp(3)OpTemp(°C)DeviceMarking(4/5)SamplesADS7251IRTERACTIVEWQFNRTE163000Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to1257251ADS7251IRTETACTIVEWQFNRTE16250Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to1257251ADS7851IRTERACTIVEWQFNRTE163000Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to1257851ADS7851IRTETACTIVEWQFNRTE16250Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to1257851(1)Themarketingstatusvaluesaredefinedasfollows:ACTIVE:Productdevicerecommendedfornewdesigns.
LIFEBUY:TIhasannouncedthatthedevicewillbediscontinued,andalifetime-buyperiodisineffect.
NRND:Notrecommendedfornewdesigns.
Deviceisinproductiontosupportexistingcustomers,butTIdoesnotrecommendusingthispartinanewdesign.
PREVIEW:Devicehasbeenannouncedbutisnotinproduction.
Samplesmayormaynotbeavailable.
OBSOLETE:TIhasdiscontinuedtheproductionofthedevice.
(2)EcoPlan-Theplannedeco-friendlyclassification:Pb-Free(RoHS),Pb-Free(RoHSExempt),orGreen(RoHS&noSb/Br)-pleasecheckhttp://www.
ti.
com/productcontentforthelatestavailabilityinformationandadditionalproductcontentdetails.
TBD:ThePb-Free/Greenconversionplanhasnotbeendefined.
Pb-Free(RoHS):TI'sterms"Lead-Free"or"Pb-Free"meansemiconductorproductsthatarecompatiblewiththecurrentRoHSrequirementsforall6substances,includingtherequirementthatleadnotexceed0.
1%byweightinhomogeneousmaterials.
Wheredesignedtobesolderedathightemperatures,TIPb-Freeproductsaresuitableforuseinspecifiedlead-freeprocesses.
Pb-Free(RoHSExempt):ThiscomponenthasaRoHSexemptionforeither1)lead-basedflip-chipsolderbumpsusedbetweenthedieandpackage,or2)lead-baseddieadhesiveusedbetweenthedieandleadframe.
ThecomponentisotherwiseconsideredPb-Free(RoHScompatible)asdefinedabove.
Green(RoHS&noSb/Br):TIdefines"Green"tomeanPb-Free(RoHScompatible),andfreeofBromine(Br)andAntimony(Sb)basedflameretardants(BrorSbdonotexceed0.
1%byweightinhomogeneousmaterial)(3)MSL,PeakTemp.
-TheMoistureSensitivityLevelratingaccordingtotheJEDECindustrystandardclassifications,andpeaksoldertemperature.
(4)Theremaybeadditionalmarking,whichrelatestothelogo,thelottracecodeinformation,ortheenvironmentalcategoryonthedevice.
(5)MultipleDeviceMarkingswillbeinsideparentheses.
OnlyoneDeviceMarkingcontainedinparenthesesandseparatedbya"~"willappearonadevice.
IfalineisindentedthenitisacontinuationofthepreviouslineandthetwocombinedrepresenttheentireDeviceMarkingforthatdevice.
(6)Lead/BallFinish-OrderableDevicesmayhavemultiplematerialfinishoptions.
Finishoptionsareseparatedbyaverticalruledline.
Lead/BallFinishvaluesmaywraptotwolinesifthefinishvalueexceedsthemaximumcolumnwidth.
PACKAGEOPTIONADDENDUMwww.
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TIbasesitsknowledgeandbeliefoninformationprovidedbythirdparties,andmakesnorepresentationorwarrantyastotheaccuracyofsuchinformation.
Effortsareunderwaytobetterintegrateinformationfromthirdparties.
TIhastakenandcontinuestotakereasonablestepstoproviderepresentativeandaccurateinformationbutmaynothaveconducteddestructivetestingorchemicalanalysisonincomingmaterialsandchemicals.
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InnoeventshallTI'sliabilityarisingoutofsuchinformationexceedthetotalpurchasepriceoftheTIpart(s)atissueinthisdocumentsoldbyTItoCustomeronanannualbasis.
TAPEANDREELINFORMATION*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQReelDiameter(mm)ReelWidthW1(mm)A0(mm)B0(mm)K0(mm)P1(mm)W(mm)Pin1QuadrantADS7251IRTERWQFNRTE163000330.
012.
43.
33.
31.
18.
012.
0Q2ADS7251IRTETWQFNRTE16250180.
012.
43.
33.
31.
18.
012.
0Q2ADS7851IRTERWQFNRTE163000330.
012.
43.
33.
31.
18.
012.
0Q2ADS7851IRTETWQFNRTE16250180.
012.
43.
33.
31.
18.
012.
0Q2PACKAGEMATERIALSINFORMATIONwww.
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0367.
035.
0ADS7251IRTETWQFNRTE16250210.
0185.
035.
0ADS7851IRTERWQFNRTE163000367.
0367.
035.
0ADS7851IRTETWQFNRTE16250210.
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0PACKAGEMATERIALSINFORMATIONwww.
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买方在下订单前应获取最新的相关信息,并验证这些信息是否完整且是最新的.
TI公布的半导体产品销售条款(http://www.
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另有其他条款可能适用于其他类型TI产品及服务的使用或销售.
复制TI数据表上TI信息的重要部分时,不得变更该等信息,且必须随附所有相关保证、条件、限制和通知,否则不得复制.
TI对该等复制文件不承担任何责任.
第三方信息可能受到其它限制条件的制约.
在转售TI产品或服务时,如果存在对产品或服务参数的虚假陈述,则会失去相关TI产品或服务的明示或暗示保证,且构成不公平的、欺诈性商业行为.
TI对此类虚假陈述不承担任何责任.
买方和在系统中整合TI产品的其他开发人员(总称"设计人员")理解并同意,设计人员在设计应用时应自行实施独立的分析、评价和判断,且应全权负责并确保应用的安全性,及设计人员的应用(包括应用中使用的所有TI产品)应符合所有适用的法律法规及其他相关要求.
设计人员就自己设计的应用声明,其具备制订和实施下列保障措施所需的一切必要专业知识,能够(1)预见故障的危险后果,(2)监视故障及其后果,以及(3)降低可能导致危险的故障几率并采取适当措施.
设计人员同意,在使用或分发包含TI产品的任何应用前,将彻底测试该等应用和该等应用中所用TI产品的功能.
TI提供技术、应用或其他设计建议、质量特点、可靠性数据或其他服务或信息,包括但不限于与评估模块有关的参考设计和材料(总称"TI资源"),旨在帮助设计人员开发整合了TI产品的应用,如果设计人员(个人,或如果是代表公司,则为设计人员的公司)以任何方式下载、访问或使用任何特定的TI资源,即表示其同意仅为该等目标,按照本通知的条款使用任何特定TI资源.
TI所提供的TI资源,并未扩大或以其他方式修改TI对TI产品的公开适用的质保及质保免责声明;也未导致TI承担任何额外的义务或责任.
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除特定TI资源的公开文档中明确列出的测试外,TI未进行任何其他测试.
设计人员只有在开发包含该等TI资源所列TI产品的应用时,才被授权使用、复制和修改任何相关单项TI资源.
但并未依据禁止反言原则或其他法理授予您任何TI知识产权的任何其他明示或默示的许可,也未授予您TI或第三方的任何技术或知识产权的许可,该等产权包括但不限于任何专利权、版权、屏蔽作品权或与使用TI产品或服务的任何整合、机器制作、流程相关的其他知识产权.
涉及或参考了第三方产品或服务的信息不构成使用此类产品或服务的许可或与其相关的保证或认可.
使用TI资源可能需要您向第三方获得对该等第三方专利或其他知识产权的许可.
TI资源系"按原样"提供.
TI兹免除对资源及其使用作出所有其他明确或默认的保证或陈述,包括但不限于对准确性或完整性、产权保证、无屡发故障保证,以及适销性、适合特定用途和不侵犯任何第三方知识产权的任何默认保证.
TI不负责任何申索,包括但不限于因组合产品所致或与之有关的申索,也不为或对设计人员进行辩护或赔偿,即使该等产品组合已列于TI资源或其他地方.
对因TI资源或其使用引起或与之有关的任何实际的、直接的、特殊的、附带的、间接的、惩罚性的、偶发的、从属或惩戒性损害赔偿,不管TI是否获悉可能会产生上述损害赔偿,TI概不负责.
除TI已明确指出特定产品已达到特定行业标准(例如ISO/TS16949和ISO26262)的要求外,TI不对未达到任何该等行业标准要求而承担任何责任.
如果TI明确宣称产品有助于功能安全或符合行业功能安全标准,则该等产品旨在帮助客户设计和创作自己的符合相关功能安全标准和要求的应用.
在应用内使用产品的行为本身不会配有任何安全特性.
设计人员必须确保遵守适用于其应用的相关安全要求和标准.
设计人员不可将任何TI产品用于关乎性命的医疗设备,除非已由各方获得授权的管理人员签署专门的合同对此类应用专门作出规定.
关乎性命的医疗设备是指出现故障会导致严重身体伤害或死亡的医疗设备(例如生命保障设备、心脏起搏器、心脏除颤器、人工心脏泵、神经刺激器以及植入设备).
此类设备包括但不限于,美国食品药品监督管理局认定为III类设备的设备,以及在美国以外的其他国家或地区认定为同等类别设备的所有医疗设备.
TI可能明确指定某些产品具备某些特定资格(例如Q100、军用级或增强型产品).
设计人员同意,其具备一切必要专业知识,可以为自己的应用选择适合的产品,并且正确选择产品的风险由设计人员承担.
设计人员单方面负责遵守与该等选择有关的所有法律或监管要求.
设计人员同意向TI及其代表全额赔偿因其不遵守本通知条款和条件而引起的任何损害、费用、损失和/或责任.
邮寄地址:上海市浦东新区世纪大道1568号中建大厦32楼,邮政编码:200122Copyright2017德州仪器半导体技术(上海)有限公司