TTL和带缓冲的TTL信号.docx

TTL和带缓冲的TTL信号.docx

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TTL和带缓冲的TTL信号

TTL和带缓冲的TTL信号

TTLandbufferedTTLsignals,.Txtdonotbelieveinforever,donothaveexpectations,donotneedapromise,whenyoucannolongerhave,theonlythingyoucandoistomakeyourselfnottoforget.TheprinceisabletoexportandunitaryverticalbeautyisbecausetheprinceeyesstarheartIcanexportHuanQiuxingwhatTTL（gate）

ThefullnameTransistor-TransistorLogic,thatis,BJT-BJTlogicgatecircuit,isacommonlogicgatecircuitindigitalelectronictechnology.Ithasbeenappliedearlierandthetechnologyhasbeenmoremature.TTLismainlycomposedofBJT（Bipolar,Junction,Transistor,bipolarjunctiontransistor,transistor）andresistor,withthecharacteristicsoffastspeed.TheearliestTTLgatecircuitisthe74series,andlaterappearedinthe74Hseries,74Lseries,74LS,74AS,74ALSandotherseries.However,TTLisgraduallybeingreplacedbyCMOScircuitbecauseofitslargepowerconsumption.

TheTTLgatecircuithas74（commercial）and54（military）twoseries,eachserieshasanumberofsubseries.

TTLlevelsignal:

TTLlevelsignalisusedatmostisusuallybecauseofdatarepresentationusingbinaryrules,+5Visequivalenttologic"1",0Visequivalenttologic"0",whichiscalledTTL（transistortransistorlogiclevel）signalsystem,thisisthestandardcommunicationtechnologybetweencomputerprocessorcontrolequipmentparts.

DatatransmissionofTTLsignalprocessorforcomputercontrolequipmentinsideisideal,thefirstcomputerdatatransmissionprocessorcontrolinsidetheequipmentisnothighforthepowersupplyandtheheatlossislow,theotherTTLsignaldirectlywiththeintegratedcircuitwithouttheneedforexpensivelinedriverandreceivercircuit;moreover,theinternaldevicedatatransmissioncomputerprocessorcontrolisperformedinhighspeed,andTTLinterfaceoperationcanmeetthisrequirement.TTLtypecommunicationusesparalleldatatransmissioninmostcases,whileparalleldatatransmissionisnotsuitablefordistancesofover10feet.Thisisduetothetwosidesofreliabilityandcost.Becausetheparallelinterfaceexistsinpartialandasymmetry,theseproblemshaveinfluenceonthereliability;inadditiontotheparalleldatatransmission,cableandconnectorcostthantheserialcommunicationwayisabithigher.

1,TTLlevel

Outputhighlevel>2.4V,outputlowlevel<0.4V.Atroomtemperature,thegeneraloutputis3.5Vhighandtheoutputlowis0.2V.Minimuminputhighandlow:

inputhighlevel>=2.0V,inputlowlevel<=0.8V,noisemarginis0.4V.

2,CMOSlevel:

The1logiclevelvoltageapproachesthesupplyvoltage,andthe0logicleveliscloseto0V.Andithasawidenoisemargin.

3levelconversioncircuit:

BecausethevaluesofTTLandCOMSaredifferent（TTL=5v<==>cmos3.3V）,thelevelconversionisrequiredwhenconnectingtoeachother:

twolevelsofresistanceareappliedtothevoltagedivider.

4,OCgate,thatis,opencollectorgatecircuit,ODgate,thatis,opendraingatecircuit,mustbeoutsidethepull-upresistorandpowertoswitchthelevelashighandlowlevel.

Otherwise,itisgenerallyusedasaswitch,largevoltageandhighcurrentload,soitisalsocalleddrivegatecircuit.

5,theTTLandCOMScircuitsarecompared:

1）theTTLcircuitisacurrentcontroldevice,andtheCOMScircuitisavoltagecontroldevice.

2）theTTLcircuitisfastandhasshorttransmissiondelay（5-10ns）,butthepowerconsumptionislarge.TheCOMScircuitisslowinspeedandlongintransmissiondelay（25-50ns）,butthepowerconsumptionislow.ThepowerconsumptionoftheCOMScircuitisrelatedtothepulsefrequencyoftheinputsignal.Thehigherthefrequency,thehotterthechipset,whichisnormal.

3）lockingeffectofCOMScircuit:

Becauseofthelargeinputcurrent,theinternalcurrentoftheCOMScircuitincreasesdramatically.Unlessthepoweriscutoff,thecurrentisincreasing.Thiseffectisthelockingeffect.Whenthelockeffectisgenerated,theinternalcurrent

oftheCOMScanreachover40mAandthechipcanbeburnedeasily.

Defensivemeasures:

1）addaclampingcircuitattheinputandoutputsothattheinputandoutputarenomorethanthespecifiedvoltage.

2）addingdecouplingcircuittothepowerinputofthechiptopreventtheVDDterminalfromtransienthighvoltage.

3）lineflowresistancebetweentheVDDandtheexternalpower,evenifthereisalargecurrentdonotletitgo.

4）whenthesystemismadeupofpowersupply,theswitchshallbeinthefollowingorder:

open,firstopentheCOMSpowersupplycircuit,andthenopentheinputsignalandtheloadpowersupply;whenclosed,shutofftheinputsignalandthepowersupplyoftheload,thenturnoffthepowercircuitCOMS.

6,theuseofCOMScircuitnotes

1）COMScircuitvoltagecontroldevice,itstotalinputresistanceisgreat,theabilitytocapturetheinterferencesignalisverystrong.Therefore,theunusedpinsshouldnotbeleftvacantandshouldbeconnectedwithapull-upresistororapull-downresistortogivethemaconstantlevel.

2）whentheinputterminalreceivesthesignalsourceofthelowergroup,theseriescurrentlimitingresistormustbeconnectedbetweentheinputandthesignalsource,sothatthe

inputcurrentislimitedto1mA.

3）whenalongsignaltransmissionlineisreceived,thematchingresistorisconnectedattheendoftheCOMScircuit.

4）whentheinputterminalisconnectedtoalargecapacitor,theinputandcapacitorshouldbeprotectedindirectly.TheresistancevalueisR=V0/1mA.V0,whichisthevoltageontheexternalcapacitor.

5）COMSinputcurrentover1mA,itmayburnCOMS.

7,theinputloadcharacteristicsoftheTTLgatecircuit（inputwithresistance,specialcaseprocessing）:

1）whenthesuspensionisequivalenttotheinputterminalhighlevel.Becausethiscanbeseenasaninputwithaninfiniteresistor.

2）aftertheinputofthegatecircuitisconnectedinserieswiththe10Kresistor,thentheinputislow,andtheinputishighinsteadoflowlevel.BecauseoftheTTLgateinputloadcharacteristicthat,onlyintheinputendisconnectedinseriesresistancelessthan910ohm,itsinputlowlevelsignaltothegatecircuitisidentified,theseriesresistanceandtheninputhasbeenshowingahighlevel.Thismustpayattention.TheCOMSgatecircuitdoesn'tneedtobeconsidered.

8,theTTLcircuithasanopencollectorOCgate,andtheMOStubealsohasanopendrainODgatecorrespondingtothecollector.Itsoutputiscalledanopendrainoutput.TheOC

gatehasaleakagecurrentatthecut-off,whichistheleakagecurrent,

Whyistherealeakagecurrent?

That'sbecausewhenthethreetubegoesoff,itsbasecurrentisabout0,butit'snotreally0,andthecollectorcurrentthroughthetransistorisnotreally0,butabout0.Andthisistheleakagecurrent.Opendrainoutput:

theoutputoftheOCgateisopendrainoutput;theoutputoftheODgateisalsoopendrainoutput.Itcanabsorblargecurrent,butcannotoutputoutwardcurrent.Therefore,inordertoinputandoutputcurrent,itshouldbeusedinconjunctionwiththepowersupplyandpull-upresistors.TheODgateisgenerallyusedasoutputbuffer/driver,levelconverter,andtomeettherequirementofabsorbinglargeloadcurrent.

9,whatiscalledtotempole?

What'sthedifferencebetweenitandopendraincircuit?

IntheTTLintegratedcircuit,theoutputwithapull-uptriodeiscalledthetotempoleoutput,andnooneiscalledtheOCgate.BecauseTTLisathreelevelpass,totempole,thatis,twothreestagepush-pulltubeconnected.Sopushpullistotem.Generaltotemtypeoutput,highlevel400UA,lowlevel8MA

WhatistheTTLlevel,whatistheCMOSlevelandwhat'stheirdifference?

The1.CMOSisafieldeffecttransistorandtheTTLisabipolartransistor

2.COMSlogiclevelrangeisrelativelylarge（5~15V）,TTLcanonlyworkunder5V

Thereisabigdifferencebetweenthehighandlowlevelof3.CMOS,theanti-interferenceisstrong,theTTLissmall,andtheanti-interferenceabilityispoor

4.CMOSpowerconsumptionisverysmall,TTLpowerconsumptionislarger（1~5mA/gates）

5.CMOSworksataslightlylowerfrequencythantheTTL,butthespeedoftheCMOSisalmostthesameasthatoftheTTL.

TTLhighlevel3.6~5V,lowlevel0V~2.4V

CMOSlevelVcccanreach12V

TheCMOScircuitoutputsahighlevelofabout0.9Vcc,whiletheoutputislowlevelapproximately

0.1Vcc.

CMOScircuitdoesnotusetheinputcannotbeleftvacant,itwillcauseconfusion.

TTLcircuitisnotused,theinputissuspendedtohighlevel

Inaddition,thepowersupplyvoltageoftheCMOSintegratedcircuitcanbechangedinalargerange,sotherequirementofthepowersupplyisnotasstrictasthatoftheTTLintegratedcircuit.

TheycanbecompatiblewiththeTTLlevel

TTL:

Transistor-TransistorLogic,thatis,logicgatecircuit

CMOS:

ComplementaryMetalOxideSemiconductor

ComplementaryMOSintegratedcircuitcomposedofcomplementarymetaloxides（PMOStubesandNMOStubes）

Itcanbeinterconnectedandcanbeusedindigitalintegratedcircuits.

SeveralproblemsneedingattentioninusingCMOSintegratedcircuit

Accordingtothenatureoftransistors,integratedcircuitsaredividedintotwomajorcategories:

TTLandCMOS.TTLisknownforitsspeed,andCMOSisknownforitslowpowerconsumption.Amongthem,CMOScircuithasbecomethemostwidelyusedintegratedcircuitbecauseofitsexcellentcharacteristics.WhenusingCMOSintegratedcircuitinelectronicproduction,inadditiontoreadingtheproductdescriptionorrelevantdatacarefully,andunderstandingthepindistributionandlimitparameter,weshouldpayattentiont