DM74LS123 Datasheet, PDF (1/6 Pages) Fairchild Semiconductor – Dual Retriggerable One-Shot with Clear and Complementary Outputs

March 1991
DM74LS123 Dual Retriggerable One-Shot
with Clear and Complementary Outputs
General Description
The DM74LS123 is a dual retriggerable monostable multivi-
brator capable of generating output pulses from a few nano-
seconds to extremely long duration up to 100% duty cycle
Each device has three inputs permitting the choice of either
leading edge or trailing edge triggering Pin (A) is an active-
low transition trigger input and pin (B) is an active-high tran-
sition trigger input The clear (CLR) input terminates the out-
put pulse at a predetermined time independent of the timing
components The clear input also serves as a trigger input
when it is pulsed with a low level pulse transition ( ) To
obtain the best trouble free operation from this device
please read the operating rules as well as the NSC one-shot
application notes carefully and observe recommendations
Features
Y _{DC triggered from active-high transition or active-low}
transition inputs
Y _{Retriggerable to 100% duty cycle}
Y _{Compensated for VCC and temperature variations}
Y _{Triggerable from CLEAR input}
Y _{DTL TTL compatible}
Y _{Input clamp diodes}
Functional Description
The basic output pulse width is determined by selection of
an external resistor (R_X) and capacitor (C_X) Once triggered
the basic pulse width may be extended by retriggering the
gated active-low transition or active-high transition inputs or
be reduced by use of the active-low or CLEAR input Retrig-
gering to 100% duty cycle is possible by application of an
input pulse train whose cycle time is shorter than the output
cycle time such that a continuous ‘‘HIGH’’ logic state is
maintained at the ‘‘Q’’ output
Connection Diagram
Function Table
Dual-In-Line Package
Inputs
CLEAR
A
B
L
X
X
X
H
X
X
X
L
H
L
u
H
v
H
u
L
H
H e High Logic Level
L e Low Logic Level
X e Can Be Either Low or High
u e Positive Going Transition
v e Negative Going Transition
e A Positive Pulse
e A Negative Pulse
Outputs
Q
Q
L
H
L
H
L
H
TL F 6386 – 1
Order Number DM74LS123M or DM74LS123N
See NS Package Number M16A or N16E
C1995 National Semiconductor Corporation TL F 6386
RRD-B30M105 Printed in U S A