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MM54HC123AJ-MM74HC123AJ
Dual Retriggerable Monostable Multivibrator
TL/F/5206
MM54HC123A/MM74HC123A
Dual
Retriggerable
Monostable
Multivibrator
January 1988
MM54HC123A/MM74HC123A
Dual Retriggerable Monostable Multivibrator
General Description
The MM54/74HC123A high speed monostable multivibra-
tors (one shots) utilize advanced silicon-gate CMOS tech-
nology. They feature speeds comparableto low power
Schottky TTL circuitry while retainingthelow power and
high noise immunity characteristicof CMOS circuits.
Each multivibrator features botha negative,A,anda posi-
tive,B, transition triggered input, eitherof which canbe
usedasan inhibit input. Also includedisa clear inputthat
when takenlow resetsthe one shot. The ’HC123 canbe
triggeredonthe positive transitionofthe clear whileAis
heldlowandBis held high.
The ’HC123Ais retriggerable. Thatisit maybe triggered
repeatedly while their outputsare generatinga pulseand
the pulsewillbe extended.
Pulse width stability overa wide rangeof temperatureand
supplyis achieved using linear CMOS techniques.Theout-
put pulseequationis simply: PWe(REXT)(CEXT); wherePWin seconds,Risin ohms,andCisin farads.All inputsare
protected from damagedueto static dischargeby diodesto
VCCand ground.
Features Typical propagation delay:25ns Wide power supply range: 2V–6V Low quiescent current:80mA maximum (74HC Series) Low input current:1mA maximum Fanoutof10 LS-TTL loads Simple pulse width formulaTeRC Wide pulse range: 400nsto% (typ) Parttopart variation: g5% (typ) Schmitt TriggerA&B inputs enable infinite signal input
riseandfall times.
Connection Diagram
Dual-In-Line Package
TL/F/5206–1
Top View
Order Number MM54HC123Aor MM74HC123A
Timing Component
TL/F/5206–2
Note:Pin6andPin14mustbe
hard-wiredto GND.
Truth Table
Inputs Outputs
Clear AB Q Q X L H X L H L L H u Éß v H Éß LH Éße High LeveleLow Level TransitionfromLowtoHigh TransitionfromHightoLoweOneHigh Level PulseeOneLow Level Pulsee Irrelevant
C1995National SemiconductorCorporation RRD-B30M105/PrintedinU.S.A.
