【74122 TTL 可再触发单稳态多谐振荡器】 单稳态多谐振荡器

DM74LS122

RetriggerableOne-ShotwithClearandComplementaryOutputs

GeneralDescription

TheDM74LS122isaretriggerablemonostablemultivipatorfeaturingbothpositiveandnegativeedgetriggeringwithcomplementaryoutputs.Aninternal10kΩtimingresistorisprovidedfordesignconvenienceminimizingcomponentcountandlayoutproblems.Thisdevicecanbeusedwithasingleexternalcapacitor.The’LS122hastwoactive-lowtransitiontriggeringinputs(A),twoactive-hightransitiontrig-geringinputs(B),andaCLEARinputthatterminatestheout-putpulsewidthatapredeterminedtimeindependentofthetimingcomponents.Theclear(CLR)inputalsoservesasatriggerinputwhenitispulsedwithalowlevelpulsetransition(J).ToobtainoptimumandtroublefreeoperationpleasereadoperatingrulesandNSCone-shotapplicationnotescarefullyandobserverecommendations.

nnnnnn

Retriggerableto100%dutycycle

Over-ridingclearterminatesoutputpulseInternal10kΩtimingresistorTTL,DTLcompatible

CompensatedforVCCandtemperaturevariationsInputclampdiodes

FunctionalDescription

ThebasicoutputpulsewidthisdeterminedbyselectionoftheinternalresistorRINToranexternalresistor(RX)andca-pacitor(CX).Oncetriggered,theoutputpulsewidthmaybeextendedbyretriggeringthegatedactive-low(A)transitioninputsortheactive-hightransition(B)inputsortheCLEARinput.Theoutputpulsewidthcanbereducedorterminatedbyoverridingitwiththeactive-lowCLEARinput.

Features

nDCtriggeredfromactive-hightransitionoractive-lowtransitioninputs

ConnectionDiagram

Dual-In-LinePackage

FunctionTable

Inputs

CLEARLXXXHHHHHHH

DS006385-1

Outputs

B1XXLX

↑

A1XHXXLLXXH

↓↓

A2XHXXXXLL

↓↓

B2XXXLH

↑

QLLLL

IIIIIIIII

QHHHH

JJJJJJJJJ

H

↑

H

↑

HHHHHH

HHHHH

HXL

↑↑

LX

OrderNumberDM74LS122MorDM74LS122N

SeePackageNumberM14AorN14A

H=HighLogicLevelL=LowLogicLevel

X=CanBeEitherLoworHigh↑=PositiveGoingTransition↓=NegativeGoingTransitionI=APositivePulseJ=ANegativePulse

AbsoluteMaximumRatings(Note1)

SupplyVoltageInputVoltage

7V7V

OperatingFreeAirTemperatureRangeDM74LS

StorageTemperature

0˚Cto+70˚C−65˚Cto+150˚C

RecommendedOperatingConditions

SymbolVCCVIHVILIOHIOLtW

SupplyVoltage

HighLevelInputVoltageLowLevelInputVoltageHighLevelOutputCurrentLowLevelOutputCurrentPulseWidth(Note7)

REXTCEXTCWIRETA

ExternalTimingResistorExternalTimingCapacitanceWiringCapacitanceatREXT/CEXTTerminal

FreeAirOperatingTemperature

70

˚C

Note1:The“AbsoluteMaximumRatings”arethosevaluesbeyondwhichthesafetyofthedevicecannotbeguaranteed.Thedeviceshouldnotbeoperatedattheselimits.Theparametricvaluesdefinedinthe“ElectricalCharacteristics”tablearenotguaranteedattheabsolutemaximumratings.The“RecommendedOperatingConditions”tablewilldefinetheconditionsforactualdeviceoperation.

ParametersMin4.752

Nom5

Max5.250.8−0.48

UnitsVVVmAmAns

AorBHighAorBLowClearLow

4040405

NoRestriction

50260

kΩµFpF

ElectricalCharacteristics

overrecommendedoperatingfreeairtemperaturerange(unlessotherwisenoted)SymbolVIVOHVOL

Parameter

InputClampVoltageHighLevelOutputVoltage

LowLevelOutputVoltage

IIIIHIILIOSICC

InputCurrent@MaxInputVoltage

HighLevelInputCurrentLowLevelInputCurrentShortCircuitOutputCurrentSupplyCurrent

VCC=Max,VI=2.7VVCC=Max,VI=0.4VVCC=Max

(Note3)

VCC=Max(Notes4,5,6)

20−0.4

−20

6

−10011

µAmAmAmA

Conditions

VCC=Min,I=−18mAVCC=Min,IOH=MaxVIL=Max,VIH=MinVCC=Min,IOL=MaxVIL=Max,VIH=MinIOL=4mA,VCC=MinVCC=Max,VI=7V

Min

Typ(Note2)

−1.5

2.7

3.40.350.25

0.5

V

0.40.1

mAVV

Max

Units

SwitchingCharacteristics

atVCC=5VandTA=25˚C

RL=2kΩ

Symbol

Parameter

From(Input)To(Output)

CL=15pFCEXT=0pF,REXT=5kΩMin

tPLH

PropagationDelayTimeLowtoHighLevelOutput

AtoQ

Max33

CL=15pFCEXT=1000pF,REXT=10kΩMin

Max

nsUnits

SwitchingCharacteristics

atVCC=5VandTA=25˚C

(Continued)

RL=2kΩ

Symbol

Parameter

From(Input)To(Output)

CL=15pFCEXT=0pF,REXT=5kΩMin

tPLHtPHLtPHLtPLHtPHLtWQ(Min)tW(out)

PropagationDelayTimeLowtoHighLevelOutputPropagationDelayTimeHightoLowLevelOutputPropagationDelayTimeHightoLowLevelOutputPropagationDelayTimeLowtoHighLevelOutputPropagationDelayTimeHightoLowLevelOutputMinimumWidthofPulseatOutputQOutputPulseWidth

AorBtoQ

4

5

µs

Note2:AlltypicalsareatVCC=5V,TA=25˚C.

Note3:Notmorethanoneoutputshouldbeshortedatatime,andthedurationshouldnotexceedonesecond.

Note4:QuiescentICCismeasured(afterclearing)with2.4VappliedtoallclearandAinputs,Binputsgrounded,alloutputsopen,CEXT=0.02µF,andREXT=25kΩ.

Note5:ICCismeasuredinthetriggeredstatewith2.4VappliedtoallclearandBinputs,Ainputsgrounded,alloutputsopen,CEXT=0.02µF,andREXT=25kΩ.Note6:Withalloutputsopenand4.5Vappliedtoalldataandclearinputs,ICCismeasuredafteramomentaryground,then4.5Visappliedtotheclock.Note7:TA=25˚CandVCC=5V.

CL=15pFCEXT=1000pF,REXT=10kΩMin

Max

Units

Max[1**********]00

BtoQAtoBtoCleartoQCleartoQAorBtoQ

nsnsnsnsnsns

OperatingRules

1.2.

Tousetheinternal10kΩtimingresistor,connecttheRINTpintoVCC.

Anexternalresistor(RX)ortheinternalresistor(10kΩ)andanexternalcapacitor(CX)arerequiredforproperoperation.ThevalueofCXmayvaryfrom0toanynec-essaryvalue.Forsmalltimeconstantsusehigh-qualitymica,glass,polypropylene,polycarbonate,orpolysty-renecapacitors.Forlargetimeconstantsusesolidtan-talumorspecialaluminumcapacitors.Ifthetimingca-pacitorshaveleakagesapproaching100nAorifstraycapacitancefromeitherterminaltogroundisgreaterthan50pFthetimingequationsmaynotrepresentthepulsewidththedevicegenerates.

3.Thepulsewidthisessentiallydeterminedbyexternal

timingcomponentsRXandCX.ForCX>1000pFtheoutputisdefinedas:

TW=KRXCX

where[RXisinkΩ]

[CXisinpF][TWisinns]K≈0.37

TheKfactorisnotaconstant,but,varieswithCX.SeeFigure2.

4.TheswitchingdioderequiredformostTTLone-shots

whenusinganelectrolytictimingcapacitorisnotneededforthe’LS122andshouldnotbeused.

5.Toobtainvariablepulsewidthbyremotetrimming,the

followingcircuitisrecommended:

6.Theretriggerablepulsewidthiscalculatedasshownbe-low:

T=TW+tPLH=0.50xRXxCX+TPLH

Theretriggeredpulsewidthisequaltothepulsewidthplusadelaytimeperiod(Figure4).

7.OutputpulsewidthvariationversusVCCandoperation

temperatures:Figure5depictstherelationshipbetweenpulsewidthvariationversusVCC;andFigure6depictspulsewidthvariationversustemperatures.

8.UnderanyoperatingconditionCXandRXmustbekept

asclosetotheone-shotdevicepinsaspossibletomini-mizestraycapacitance,toreducenoisepick-up,andtoreduceI-RandLdi/dtvoltagedevelopedalongtheircon-nectingpaths.IftheleadlengthfromCXtopins(13)and(11)isgreaterthan3cm,forexample,theoutputpulsewidthmightbequitedifferentfromvaluespredictedfromtheappropriateequations.Anon-inductiveandlowca-pacitivepathisnecessarytoensurecompletedischargeofCXineachcycleofitsoperationsothattheoutputpulsewidthwillbeaccurate.

3

OperatingRules

9.

(Continued)

VCCandgroundwiringshouldconformtogoodhigh-frequencystandardsandpracticessothatswitch-ingtransientsontheVCCandgroundreturnleadsdonotcauseinteractionbetweenone-shots.A0.01µFto0.10µFbypasscapacitor(diskceramicormonolithictype)fromVCCtogroundisnecessaryoneachdevice.Furthermore,thebypasscapacitorshouldbelocatedasclosetotheVCCpinasspacepermits.

DS006385-4

Note:“Rremote”shouldbeasclosetothedevicepinsaspossible.

FIGURE3.

Note:Forfurtherdetaileddevicecharacteristicsandoutputperfor-mancepleaserefertotheNSCone-shotapplicationnoteAN-366.

DS006385-2

FIGURE1.

DS006385-6

FIGURE5.

DS006385-3

FIGURE2.

DS006385-7

FIGURE6.

4

PhysicalDimensions

inches(millimeters)unlessotherwisenoted

DM74LS122RetriggerableOne-ShotwithClearandComplementaryOutputs

LIFESUPPORTPOLICY

FAIRCHILD’SPRODUCTSARENOTAUTHORIZEDFORUSEASCRITICALCOMPONENTSINLIFESUPPORTDE-VICESORSYSTEMSWITHOUTTHEEXPRESSWRITTENAPPROVALOFTHEPRESIDENTOFFAIRCHILDSEMI-CONDUCTORCORPORATION.Asusedherein:

2.Acriticalcomponentinanycomponentofalifesupport1.Lifesupportdevicesorsystemsaredevicesorsys-deviceorsystemwhosefailuretoperformcanberea-temswhich,(a)areintendedforsurgicalimplantinto

sonablyexpectedtocausethefailureofthelifesupportthebody,or(b)supportorsustainlife,and(c)whose

deviceorsystem,ortoaffectitssafetyoreffectiveness.failuretoperformwhenproperlyusedinaccordance

withinstructionsforuseprovidedinthelabeling,canbereasonablyexpectedtoresultinasignificantinjurytotheuser.

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