ADC0809CCN资料

ADC0808/ADC08098-BitµPCompatibleA/DConverterswith8-ChannelMultiplexerOctober1999

ADC0808/ADC0809

8-BitµPCompatibleA/DConverterswith8-ChannelMultiplexer

GeneralDescription

TheADC0808,ADC0809dataacquisitioncomponentisamonolithicCMOSdevicewithan8-bitanalog-to-digitalcon-verter,8-channelmultiplexerandmicroprocessorcompatiblecontrollogic.The8-bitA/Dconverterusessuccessiveap-proximationastheconversiontechnique.Theconverterfea-turesahighimpedancechopperstabilizedcomparator,a256Rvoltagedividerwithanalogswitchtreeandasucces-siveapproximationregister.The8-channelmultiplexercandirectlyaccessanyof8-single-endedanalogsignals.Thedeviceeliminatestheneedforexternalzeroandfull-scaleadjustments.EasyinterfacingtomicroprocessorsisprovidedbythelatchedanddecodedmultiplexeraddressinputsandlatchedTTLTRI-STATE®outputs.

ThedesignoftheADC0808,ADC0809hasbeenoptimizedbyincorporatingthemostdesirableaspectsofseveralA/Dconversiontechniques.TheADC0808,ADC0809offershighspeed,highaccuracy,minimaltemperaturedependence,ex-cellentlong-termaccuracyandrepeatability,andconsumesminimalpower.Thesefeaturesmakethisdeviceideallysuitedtoapplicationsfromprocessandmachinecontroltoconsumerandautomotiveapplications.For16-channelmul-tiplexerwithcommonoutput(sample/holdport)seeADC0816datasheet.(SeeAN-247formoreinformation.)

Features

nEasyinterfacetoallmicroprocessors

nOperatesratiometricallyorwith5VDCoranalogspanadjustedvoltagereference

nNozeroorfull-scaleadjustrequiredn8-channelmultiplexerwithaddresslogic

n0Vto5Vinputrangewithsingle5VpowersupplynOutputsmeetTTLvoltagelevelspecificationsnStandardhermeticormolded28-pinDIPpackagen28-pinmoldedchipcarrierpackagenADC0808equivalenttoMM74C949nADC0809equivalenttoMM74C949-1

KeySpecifications

nnnnn

Resolution

TotalUnadjustedErrorSingleSupplyLowPower

ConversionTime

8Bits

±⁄LSBand±1LSB

5VDC15mW100µs

12BlockDiagram

DS005672-1

SeeOrderingInformation

TRI-STATE®isaregisteredtrademarkofNationalSemiconductorCorp.

©1999NationalSemiconductorCorporationDS005672www.national.com

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ADC0808/ADC0809ConnectionDiagrams

Dual-In-LinePackage

MoldedChipCarrierPackage

DS005672-12

DS005672-11

OrderNumberADC0808CCNorADC0809CCN

SeeNSPackageJ28AorN28A

OrderNumberADC0808CCVorADC0809CCV

SeeNSPackageV28A

OrderingInformation

TEMPERATURERANGEError

−40˚Cto+85˚C

ADC0808CCNADC0809CCNN28AMoldedDIP

ADC0808CCVADC0809CCV

V28AMoldedChipCarrier

J28ACeramicDIP

J28ACeramicDIP

ADC0808CCJ

−55˚Cto+125˚CADC0808CJ

±1⁄2LSBUnadjusted±1LSBUnadjusted

PackageOutline

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ADC0808/ADC0809AbsoluteMaximumRatings(Notes2,1)

IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheNationalSemiconductorSalesOffice/Distributorsforavailabilityandspecifications.

SupplyVoltage(VCC)(Note3)6.5VVoltageatAnyPin−0.3Vto(VCC+0.3V)ExceptControlInputsVoltageatControlInputs−0.3Vto+15V(START,OE,CLOCK,ALE,ADDA,ADDB,ADDC)StorageTemperatureRange−65˚Cto+150˚C

875mWPackageDissipationatTA=25˚C

LeadTemp.(Soldering,10seconds)Dual-In-LinePackage(plastic)260˚C

Dual-In-LinePackage(ceramic)

MoldedChipCarrierPackageVaporPhase(60seconds)Infrared(15seconds)ESDSusceptibility(Note8)

300˚C215˚C220˚C400V

(Notes1,2)

TMIN≤TA≤TMAX−40˚C≤TA≤+85˚C−40˚C≤TA≤+85˚C4.5VDCto6.0VDCOperatingConditions

TemperatureRange(Note1)ADC0808CCN,ADC0809CCNADC0808CCV,ADC0809CCVRangeofVCC(Note1)

ElectricalCharacteristics

ConverterSpecifications:VCC=5VDC=VREF+,VREF(−)=GND,TMIN≤TA≤TMAXandfCLK=0kHzunlessotherwisestated.

Symbol

Parameter

ADC0808

TotalUnadjustedError(Note5)ADC0809

TotalUnadjustedError(Note5)InputResistance

AnalogInputVoltageRange

VREF(+)Voltage,TopofLadderVoltage,CenterofLadder

VREF(−)IINVoltage,BottomofLadderComparatorInputCurrent

MeasuredatRef(−)fc=0kHz,(Note6)0˚Cto70˚CTMINtoTMAXFromRef(+)toRef(−)(Note4)V(+)orV(−)MeasuredatRef(+)

VCC/2-0.1−0.1−21.0GND−0.10

VCCVCC/202.5

VCC+0.10VCC+0.1VCC/2+0.1

25˚CTMINtoTMAXConditions

Min

Typ

Max

UnitsLSBLSBLSBLSBkΩVDCVVV

2

µA

±1⁄2±3⁄4±1±11⁄4±0.5

ElectricalCharacteristics

DigitalLevelsandDCSpecifications:ADC0808CCN,ADC0808CCV,ADC0809CCNandADC0809CCV,4.75≤VCC≤5.25V,−40˚C≤TA≤+85˚CunlessotherwisenotedSymbol

ANALOGMULTIPLEXERIOFF(+)OFFChannelLeakageCurrent

VCC=5V,VIN=5V,TA=25˚CTMINtoTMAXVCC=5V,VIN=0,TA=25˚CTMINtoTMAXCONTROLINPUTSVIN(1)VIN(0)IIN(1)IIN(0)ICCLogical“1”InputVoltageLogical“0”InputVoltageLogical“1”InputCurrent(TheControlInputs)Logical“0”InputCurrent(TheControlInputs)SupplyCurrent

fCLK=0kHz

0.3

3.0

mA

VIN=0

−1.0

µA

VIN=15V

VCC−1.5

1.51.0

VVµA

−200−1.0

−1010

2001.0

nAµAnAµA

Parameter

Conditions

Min

Typ

Max

Units

IOFF(−)OFFChannelLeakageCurrent

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ADC0808/ADC0809ElectricalCharacteristics

SymbolVOUT(1)Parameter

Logical“1”OutputVoltage

(Continued)

DigitalLevelsandDCSpecifications:ADC0808CCN,ADC0808CCV,ADC0809CCNandADC0809CCV,4.75≤VCC≤5.25V,−40˚C≤TA≤+85˚Cunlessotherwisenoted

ConditionsVCC=4.75VIOUT=−360µAIOUT=−10µAIO=1.6mAIO=1.2mAVO=5VVO=0

−3Min

Typ

Max

Units

DATAOUTPUTSANDEOC(INTERRUPT)

2.44.5

0.450.453

V(min)V(min)VVµAµA

VOUT(0)VOUT(0)IOUTLogical“0”OutputVoltageLogical“0”OutputVoltageEOCTRI-STATEOutputCurrent

ElectricalCharacteristics

TimingSpecificationsVCC=VREF(+)=5V,VREF(−)=GND,tr=tf=20nsandTA=25˚Cunlessotherwisenoted.SymboltWStWALEtstHtDtH1,tH0t1H,t0HtcfctEOCCINCOUTParameter

MinimumStartPulseWidthMinimumALEPulseWidthMinimumAddressSet-UpTimeMinimumAddressHoldTimeAnalogMUXDelayTimeFromALE

OEControltoQLogicStateOEControltoHi-ZConversionTimeClockFrequencyEOCDelayTimeInputCapacitanceTRI-STATEOutputCapacitance

Note1:AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.DCandACelectricalspecificationsdonotapplywhenoperatingthedevicebeyonditsspecifiedoperatingconditions.

Note2:AllvoltagesaremeasuredwithrespecttoGND,unlessothewisespecified.

Note3:Azenerdiodeexists,internally,fromVCCtoGNDandhasatypicalbreakdownvoltageof7VDC.

Note4:Twoon-chipdiodesaretiedtoeachanaloginputwhichwillforwardconductforanaloginputvoltagesonediodedropbelowgroundoronediodedropgreaterthantheVCCnsupply.Thespecallows100mVforwardbiasofeitherdiode.ThismeansthataslongastheanalogVINdoesnotexceedthesupplyvoltagebymorethan100mV,theoutputcodewillbecorrect.Toachieveanabsolute0VDCto5VDCinputvoltagerangewillthereforerequireaminimumsupplyvoltageof4.900VDCovertemperaturevariations,initialtoleranceandloading.

Note5:Totalunadjustederrorincludesoffset,full-scale,linearity,andmultiplexererrors.SeeFigure3.NoneoftheseA/Dsrequiresazeroorfull-scaleadjust.How-ever,ifanallzerocodeisdesiredforananaloginputotherthan0.0V,orifanarrowfull-scalespanexists(forexample:0.5Vto4.5Vfull-scale)thereferencevoltagescanbeadjustedtoachievethis.SeeFigure13.

Note6:Comparatorinputcurrentisabiascurrentintooroutofthechopperstabilizedcomparator.Thebiascurrentvariesdirectlywithclockfrequencyandhaslittletemperaturedependence(Figure6).Seeparagraph4.0.

Note7:TheoutputsofthedataregisterareupdatedoneclockcyclebeforetherisingedgeofEOC.Note8:Humanbodymodel,100pFdischargedthrougha1.5kΩresistor.

Conditions

(Figure5)(Figure5)(Figure5)(Figure5)

RS=0Ω(Figure5)

CL=50pF,RL=10k(Figure8)CL=10pF,RL=10k(Figure8)fc=0kHz,(Figure5)(Note7)(Figure5)AtControlInputsAtTRI-STATEOutputs

MInTyp10010025251125125

Max20020050502.525025011612808+2µS

UnitsnsnsnsnsµsnsnsµskHzClockPeriodspFpF

90100

1000

1010

1515

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ADC0808/ADC0809FunctionalDescription

Multiplexer.Thedevicecontainsan8-channelsingle-endedanalogsignalmultiplexer.Aparticularinputchannelisse-lectedbyusingtheaddressdecoder.Table1showstheinputstatesfortheaddresslinestoselectanychannel.Thead-dressislatchedintothedecoderonthelow-to-hightransitionoftheaddresslatchenablesignal.

TABLE1.

SELECTEDANALOGCHANNEL

IN0IN1IN2IN3IN4IN5IN6IN7

ADDRESSLINECLLLLHHHH

BLLHHLLHH

ALHLHLHLH

Thebottomresistorandthetopresistoroftheladdernet-workinFigure1arenotthesamevalueastheremainderofthenetwork.Thedifferenceintheseresistorscausestheoutputcharacteristictobesymmetricalwiththezeroandfull-scalepointsofthetransfercurve.Thefirstoutputtransi-tionoccurswhentheanalogsignalhasreached+1⁄2LSBandsucceedingoutputtransitionsoccurevery1LSBlateruptofull-scale.

Thesuccessiveapproximationregister(SAR)performs8it-erationstoapproximatetheinputvoltage.ForanySARtypeconverter,n-iterationsarerequiredforann-bitconverter.Figure2showsatypicalexampleofa3-bitconverter.IntheADC0808,ADC0809,theapproximationtechniqueisex-tendedto8bitsusingthe256Rnetwork.

TheA/Dconverter’ssuccessiveapproximationregister(SAR)isresetonthepositiveedgeofthestartconversion(SC)pulse.Theconversionisbegunonthefallingedgeofthestartconversionpulse.Aconversioninprocesswillbein-terruptedbyreceiptofanewstartconversionpulse.Con-tinuousconversionmaybeaccomplishedbytyingtheend-of-conversion(EOC)outputtotheSCinput.Ifusedinthismode,anexternalstartconversionpulseshouldbeap-pliedafterpowerup.End-of-conversionwillgolowbetween0and8clockpulsesaftertherisingedgeofstartconversion.ThemostimportantsectionoftheA/Dconverteristhecom-parator.Itisthissectionwhichisresponsiblefortheultimateaccuracyoftheentireconverter.Itisalsothecomparatordriftwhichhasthegreatestinfluenceontherepeatabilityofthedevice.Achopper-stabilizedcomparatorprovidesthemosteffectivemethodofsatisfyingalltheconverterrequire-ments.

Thechopper-stabilizedcomparatorconvertstheDCinputsignalintoanACsignal.ThissignalisthenfedthroughahighgainACamplifierandhastheDClevelrestored.ThistechniquelimitsthedriftcomponentoftheamplifiersincethedriftisaDCcomponentwhichisnotpassedbytheACam-plifier.ThismakestheentireA/Dconverterextremelyinsen-sitivetotemperature,longtermdriftandinputoffseterrors.

CONVERTERCHARACTERISTICSTheConverter

Theheartofthissinglechipdataacquisitionsystemisits8-bitanalog-to-digitalconverter.Theconverterisdesignedtogivefast,accurate,andrepeatableconversionsoverawiderangeoftemperatures.Theconverterispartitionedinto3majorsections:the256Rladdernetwork,thesuccessiveap-proximationregister,andthecomparator.Theconverter’sdigitaloutputsarepositivetrue.

The256Rladdernetworkapproach(Figure1)waschosenovertheconventionalR/2Rladderbecauseofitsinherentmonotonicity,whichguaranteesnomissingdigitalcodes.Monotonicityisparticularlyimportantinclosedloopfeedbackcontrolsystems.Anon-monotonicrelationshipcancauseos-cillationsthatwillbecatastrophicforthesystem.Additionally,the256Rnetworkdoesnotcauseloadvariationsontheref-erencevoltage.

Figure4showsatypicalerrorcurvefortheADC0808asmeasuredusingtheproceduresoutlinedinAN-179.

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ADC0808/ADC0809FunctionalDescription

(Continued)

DS005672-2

FIGURE1.ResistorLadderandSwitchTree

DS005672-13

FIGURE2.3-BitA/DTransferCurve

DS005672-14

FIGURE3.3-BitA/DAbsoluteAccuracyCurve

DS005672-15

FIGURE4.TypicalErrorCurve

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ADC0808/ADC0809TimingDiagram

DS005672-4

FIGURE5.

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ADC0808/ADC0809TypicalPerformanceCharacteristics

DS005672-16

FIGURE6.ComparatorIINvsVIN(VCC=VREF=5V)

DS005672-17

FIGURE7.MultiplexerRONvsVIN(VCC=VREF=5V)

TRI-STATETestCircuitsandTimingDiagrams

t1H,tH1t1H,CL=10pF

tH1,CL=50pF

DS005672-18

DS005672-19DS005672-20

t0H,tH0t0H,CL=10pFtH0,CL=50pF

DS005672-21

DS005672-22

DS005672-23

FIGURE8.

ApplicationsInformation

OPERATION

1.0RATIOMETRICCONVERSION

TheADC0808,ADC0809isdesignedasacompleteDataAcquisitionSystem(DAS)forratiometricconversionsys-tems.Inratiometricsystems,thephysicalvariablebeingmeasuredisexpressedasapercentageoffull-scalewhichisnotnecessarilyrelatedtoanabsolutestandard.ThevoltageinputtotheADC0808isexpressedbytheequation

DX=DatapointbeingmeasuredDMAX=MaximumdatalimitDMIN=Minimumdatalimit

Agoodexampleofaratiometrictransducerisapotentiom-eterusedasapositionsensor.Thepositionofthewiperisdi-rectlyproportionaltotheoutputvoltagewhichisaratioofthefull-scalevoltageacrossit.Sincethedataisrepresentedasaproportionoffull-scale,referencerequirementsaregreatlyreduced,eliminatingalargesourceoferrorandcostformanyapplications.AmajoradvantageoftheADC0808,ADC0809isthattheinputvoltagerangeisequaltothesup-plyrangesothetransducerscanbeconnecteddirectlyacrossthesupplyandtheiroutputsconnecteddirectlyintothemultiplexerinputs,(Figure9).

Ratiometrictransducerssuchaspotentiometers,straingauges,thermistorbridges,pressuretransducers,etc.,aresuitableformeasuringproportionalrelationships;however,manytypesofmeasurementsmustbereferredtoanabso-lutestandardsuchasvoltageorcurrent.Thismeansasys-8

(1)

VIN=InputvoltageintotheADC0808Vfs=Full-scalevoltageVZ=Zerovoltage

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ADC0808/ADC0809ApplicationsInformation

(Continued)

temreferencemustbeusedwhichrelatesthefull-scalevolt-agetothestandardvolt.Forexample,ifVCC=VREF=5.12V,thenthefull-scalerangeisdividedinto256standardsteps.Thesmalleststandardstepis1LSBwhichisthen20mV.2.0RESISTORLADDERLIMITATIONS

Thevoltagesfromtheresistorladderarecomparedtotheselectedinto8timesinaconversion.Thesevoltagesarecoupledtothecomparatorviaananalogswitchtreewhichisreferencedtothesupply.Thevoltagesatthetop,centerandbottomoftheladdermustbecontrolledtomaintainproperoperation.

Thetopoftheladder,Ref(+),shouldnotbemorepositivethanthesupply,andthebottomoftheladder,Ref(−),shouldnotbemorenegativethanground.ThecenteroftheladdervoltagemustalsobenearthecenterofthesupplybecausetheanalogswitchtreechangesfromN-channelswitchestoP-channelswitches.Theselimitationsareautomaticallysat-isfiedinratiometricsystemsandcanbeeasilymetingroundreferencedsystems.

Figure10showsagroundreferencedsystemwithasepa-ratesupplyandreference.Inthissystem,thesupplymustbetrimmedtomatchthereferencevoltage.Forinstance,ifa5.12Visused,thesupplyshouldbeadjustedtothesamevoltagewithin0.1V.

DS005672-7

FIGURE9.RatiometricConversionSystem

TheADC0808needslessthanamilliampofsupplycurrentsodevelopingthesupplyfromthereferenceisreadilyac-complished.InFigure11agroundreferencedsystemisshownwhichgeneratesthesupplyfromthereference.Thebuffershowncanbeanopampofsufficientdrivetosupplythemilliampofsupplycurrentandthedesiredbusdrive,orifacapacitivebusisdrivenbytheoutputsalargecapacitorwillsupplythetransientsupplycurrentasseeninFigure12.TheLM301isovercompensatedtoinsurestabilitywhenloadedbythe10µFoutputcapacitor.

ThetopandbottomladdervoltagescannotexceedVCCandground,respectively,buttheycanbesymmetricallylessthanVCCandgreaterthanground.Thecenteroftheladdervolt-ageshouldalwaysbenearthecenterofthesupply.Thesen-sitivityoftheconvertercanbeincreased,(i.e.,sizeoftheLSBstepsdecreased)byusingasymmetricalreferencesys-tem.InFigure13,a2.5Vreferenceissymmetricallycen-teredaboutVCC/2sincethesamecurrentflowsinidenticalresistors.Thissystemwitha2.5VreferenceallowstheLSBbittobehalfthesizeofa5Vreferencesystem.

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ADC0808/ADC0809ApplicationsInformation

(Continued)

DS005672-24

FIGURE10.GroundReferenced

ConversionSystemUsingTrimmedSupply

DS005672-25

FIGURE11.GroundReferencedConversionSystemwith

ReferenceGeneratingVCCSupply

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ADC0808/ADC0809ApplicationsInformation

(Continued)

DS005672-26

FIGURE12.TypicalReferenceandSupplyCircuit

DS005672-27

RA=RB*Ratiometrictransducers

FIGURE13.SymmetricallyCenteredReference

3.0CONVERTEREQUATIONS

ThetransitionbetweenadjacentcodesNandN+1isgivenby:

TheoutputcodeNforanarbitraryinputaretheintegerswithintherange:

(4)

(2)

ThecenterofanoutputcodeNisgivenby:

Where:VIN=Voltageatcomparatorinput

VREF(+)=VoltageatRef(+)VREF(−)=VoltageatRef(−)

VTUE=Totalunadjustederrorvoltage(typicallyVREF(+)÷512)

(3)

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ADC0808/ADC0809ApplicationsInformation

4.0ANALOGCOMPARATORINPUTS

(Continued)

Thedynamiccomparatorinputcurrentiscausedbythepe-riodicswitchingofon-chipstraycapacitances.Theseareconnectedalternatelytotheoutputoftheresistorladder/switchtreenetworkandtothecomparatorinputaspartoftheoperationofthechopperstabilizedcomparator.

Theaveragevalueofthecomparatorinputcurrentvariesdi-rectlywithclockfrequencyandwithVINasshowninFigure6.

Ifnofiltercapacitorsareusedattheanaloginputsandthesignalsourceimpedancesarelow,thecomparatorinputcur-rentshouldnotintroduceconvertererrors,asthetransientcreatedbythecapacitancedischargewilldieoutbeforethecomparatoroutputisstrobed.

Ifinputfiltercapacitorsaredesiredfornoisereductionandsignalconditioningtheywilltendtoaverageoutthedynamiccomparatorinputcurrent.Itwillthentakeonthecharacteris-ticsofaDCbiascurrentwhoseeffectcanbepredictedcon-ventionally.

TypicalApplication

DS005672-10

*Addresslatchesneededfor8085andSC/MPinterfacingtheADC0808toamicroprocessor

TABLE2.MicroprocessorInterfaceTable

PROCESSOR80808085Z-80SC/MP6800

RDRDNRDSVMA•φ2•R/W

READMEMRWRITEMEMWWRWRNWDSVMA•φ•R/W

INTERRUPT(COMMENT)INTR(ThruRSTCircuit)INTR(ThruRSTCircuit)INT(ThruRSTCircuit,Mode0)SA(ThruSenseA)IRQAorIRQB(ThruPIA)

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ADC0808/ADC0809PhysicalDimensions

inches(millimeters)unlessotherwisenoted

MoldedDual-In-LinePackage(N)

OrderNumberADC0808CCNorADC0809CCN

NSPackageNumberN28B

MoldedChipCarrier(V)

OrderNumberADC0808CCVorADC0809CCV

NSPackageNumberV28A

13

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ADC0808/ADC08098-BitµPCompatibleA/DConverterswith8-ChannelMultiplexerNotes

LIFESUPPORTPOLICY

NATIONAL’SPRODUCTSARENOTAUTHORIZEDFORUSEASCRITICALCOMPONENTSINLIFESUPPORTDEVICESORSYSTEMSWITHOUTTHEEXPRESSWRITTENAPPROVALOFTHEPRESIDENTANDGENERALCOUNSELOFNATIONALSEMICONDUCTORCORPORATION.Asusedherein:1.Lifesupportdevicesorsystemsaredevicesorsystemswhich,(a)areintendedforsurgicalimplantintothebody,or(b)supportorsustainlife,andwhosefailuretoperformwhenproperlyusedinaccordancewithinstructionsforuseprovidedinthelabeling,canbereasonablyexpectedtoresultinasignificantinjurytotheuser.

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Nationaldoesnotassumeanyresponsibilityforuseofanycircuitrydescribed,nocircuitpatentlicensesareimpliedandNationalreservestherightatanytimewithoutnoticetochangesaidcircuitryandspecifications.