SGS Thomson Microelectronics M74HC123, M74HC123A Datasheet
M54HC123/123A
M74HC123/123A
DUAL RETRIGGERABLE MONOSTABLE MULTIVIBRATOR
.HIGH SPEED
tPD= 25 ns(TYP) at VCC=5V
.LOWPOWERDISSIPATION
STANDBYSTATEICC=4µA (MAX.)AT TA=25°C
ACTIVESTATE ICC=200µA (TYP.) AT VCC=5V
.HIGH NOISE IMMUNITY
V
NIH=VNIL
.OUTPUT DRIVE CAPABILITY
10 LSTTL LOADS
=28%VCC(MIN.)
B1R
(PlasticPackage)
(CeramicPackage)
.SYMMETRICALOUTPUT IMPEDANCE
IOH=IOL= 4 mA (MIN.)
.BALANCEDPROPAGATION DELAYS
t
PLH=tPHL
.WIDE OPERATINGVOLTAGERANGE
VCC(OPR)= 2V TO6 V
.WIDE OUTPUT PULSE WIDTHRANGE
t
=120ns ∼ 60 s OVER AT VCC= 4.5 V
WOUT
M1R
(MicroPackage)
ORDER CODES :
M54HC X XXF1R M74H CXXXM1R
M74HC X XXB1R M74HCX X XC1R
(Chip Carrier)
.PIN AND FUNCTION COMPATIBLE WITH
54/74LS123
F1R
C1R
DESCRIPTION
The M54/74HC123 is a high speed CMOS MONOSTABLE multivibrator fabricated with silicon gate
C2MOS technology. It achieves the high speed
operation similar to equivalent LSTTL while maintainingthe CMOS lowpower dissipation. There are
two trigger inputs,A INPUT (negative edge) and 8
INPUT (positive edge). These inputs are valid for
slowrising/falling signals,(tr= tf= Isec).The device
may also betriggered by using the CLRinput(positive-edge) because of the Schmitt-trigger input ;
after triggering the output maintains the MONOSTABLEstatefor thetime period determinedby the
external resistor Rx and capacitor Cx. When Cx ≥
10nF and Rx ≥ 10KΩ,theoutput pulse widthvalue
is approssimatively given by theformula: t
•Cx • Rx.
Two different pulse width constant are available:
K ≅ 0.45 for HC123 K ≅ 1 for HC123A.
Taking CLR low breaks this MONOSTABLE
STATE. If the next trigger pulse occurs during the
MONOSTABLEperiodit makestheMONOSTABLE
periodlonger. Limit for values ofCx and Rx :
Cx : NO LIMIT
Rx : VCC<3.0 V 5K Ω to1 M Ω
VCC≥ 3.0 V 1 K Ω to 1 M Ω
All inputs are equipped with protection circuits
w(out)
=K
PIN CONNECTIONS(top view)
NC =
No Internal
Connection
October 1993
1/14
M54/M74HC123/123A
SYSTEM DIAGRAM
TIMING CHART
2/14
M54 / M74HC1 23 /123 A
BLOCK DIAGRAM
Note:
(1)Cx, Rx, Dx are externalcomponents.
(2)Dx isa clampingdiode.
Theexternalcapacitor ischarged toVCCinthestand-by state,i.e.notrigger.Whenthesupply voltageis turned offCxis dischargedmainly
throughan internalparasiticdiode (see figures). IfCx issufficientlylarge and VCCdecreases rapidy,therewill besomepossibility of damagingtheI.C.witha surgecurrentor latch-up. If the voltagesupply filtercapacitor is largeenough and VCCdecrease slowly,the surge
currentis automaticallylimitedand damage the I.C. is avoided. Themaximumforwardcurrentof the parasiticdiodeisapproximately 20
mA.In caseswhereCx is large the timetakenfor the supply voltageto fallto 0.4VCCcanbecalculated asfollows:
tf≥ (VCC–0.7)⋅Cx/20mA
Incases wheretfistoo short anexternal clampingdiode is required toprotect theI.C.fromthe surge current.
FUNCTIONAL DESCRIPTION
STAND-BYSTATE
The external capacitor, Cx, is fully charged to V
CC
inthe stand-bystate.Hence, beforetriggering,transistorQp andQn (connected tothe Rx/Cxnode)are
both turned-off. The two comparators that control
the timing and the two reference voltage sources
stop operating. The totalsupply current istherefore
only leakage current.
TRIGGEROPERATION
Triggering occurswhen :
1 st) A is”low” andB hasa falling edge ;
2 nd) B is ”high”and Ahas a rising edge;
3 rd) AislowandB ishighand C1hasa risingedge.
After the multivibrator has been retriggered comparatorC1 and C2 start operating and Qn isturned
on. Cx then discharges through Qn.The voltageat
the node R/Cexternal falls.
When itreaches V
theoutputof comparatorC1
REFL
becomeslow.Thisinturnresets theflip-flop andQn
is turned off.
At this pointC1 stopsfunctioning but C2 continues
to operate.
ThevoltageatR/Cexternalbeginstorisewithatime
constantset by the externalcomponents Rx, Cx.
Triggering themultivibratorcausesQto gohighafter
internal delay dueto the flip-flop and the gate. Qremains high until the voltage at R/C external rises
againto V
. AtthispointC2outputgoeslow and
REFH
O goes low. C2 stop operating. That means that
after triggering when the voltage R/C external returns to V
the multivibrator has returned to its
REFH
MONOSTABLESTATE. In the case whereRx ⋅ Cx
are large enough and thedischargetime of the capacitorand thedelaytime inthe I.C.can beignored,
the width ofthe output pulse tw (out) is as follows :
t
W(OUT)
= 0.46 Cx ⋅ Rx (HC123)
t
W(OUT)
=Cx⋅Rx (HC123A)
3/14
M54/M74HC123/123A
FUNCTIONAL DESCRIPTION (continued)
RE-TRIGGEREDOPERATION
When a second trigger pulse followsthe first its ef-
fect will depend on the state of the multivibrator. If
the capacitor Cx is being charged the voltage level
of R/C external falls to Vrefl again and Q remains
high i.e.the retrigger pulse arrives in atimeshorter
than the period Rx ⋅ Cx seconds, the capacitor
charging time constant.If the second trigger pulse
is verycloseto theinitialtrigger pulseitisineffective
; i.e. thesecond triggermust arrive in the capacitor
mum time for a second trigger to be effective dependson VCCand Cx.
RESETOPERATION
CL isnormallyhigh.If CLislow,the triggeris not ef-
fectivebecauseQoutput goeslow and trigger control flip-flopis reset.
Also transistor Op is turned on and Cx is charged
quickyto VCC. Thismeans if CL inputgoes low,the
IC becomeswaiting state both inoperating andnon
operating state.
discharge cycle to be ineffective; Hence the mini-
TRUTH TABLE
INPUTS OUTPUTS
ABCLQQ
H H OUTPUT ENABLE
X L H L H INHIBIT
H X H L H INHIBIT
L H OUTPUT ENABLE
L H OUTPUT ENABLE
X X L L H INHIBIT
X:Don’t Care Z: HighImpedance
NOTE
INPUT AND OUTPUT EQUIVALENT CIRCUIT
4/14
M54 / M74HC1 23 /123 A
PIN DESCRIPTION
IEC LOGIC SYMBOL
PIN No SYMBOL NAME AND FUNCTION
1, 9 1A, 2A Trigger Inputs (Negative
Edge Triggered)
2, 10 1B, 2B Trigger Inputs (Positive
Edge Triggered)
3, 11 1CLR,
2CLR
Direct Reset LOW and
Trigger Action at Positive
Edge
4, 12 1Q, 2Q Outputs (Active LOW)
72R
EXT/CEXT
External Resistor
Capacitor Connection
13, 5 1Q, 2Q Outputs (Active HIGH)
14, 6 1C
2C
15 1R
EXT/CEXT
EXT
EXT
External Capacitor
Connection
External Resistor
Capacitor Connection
8 GND Ground (0V)
16 V
CC
Positive Supply Voltage
ABSOLU TE M AXIMU M R AT ING
Symbol Parameter Value Unit
V
CC
V
V
O
I
IK
I
OK
I
O
I
or I
CC
P
D
T
stg
T
AbsoluteMaximumRatingsarethosevalues beyondwhichdamagetothedevicemayoccur.Functionaloperationunderthesecondition isnotimplied.
(*)500 mW: ≅ 65oC derateto300mW by 10mW/oC: 65oCto85oC
Supply Voltage -0.5 to +7 V
DC Input Voltage -0.5 to VCC+ 0.5 V
I
DC Output Voltage -0.5 to VCC+ 0.5 V
DC Input Diode Current ± 20 mA
DC Output Diode Current ± 20 mA
DC Output Source Sink Current Per Output Pin ± 25 mA
DC VCCor Ground Current ± 50 mA
GND
Power Dissipation 500 (*) mW
Storage Temperature -65 to +150
Lead Temperature (10 sec) 300
L
o
C
o
C
5/14
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