TL/F/6538
54121/DM54121/DM74121
One-Shot
with
Clear
and
Complementary
Outputs
June 1989
54121/DM54121/DM74121 One-Shot with
Clear and Complementary Outputs
General Description
The DM54/74121 is a monostable multivibrator featuring
both positive and negative edge triggering with complemen-
tary outputs. An internal 2kX timing resistor is provided for
design convenience minimizing component count and lay-
out problems. This device can be used with a single external
capacitor. Inputs (A) are active-low trigger transition inputs
and input (B) is an active-high transition Schmitt-trigger in-
put that allows jitter-free triggering from inputs with tran-
sition rates as slow as 1 volt/second. A high immunity to
V
CC
noise of typically 1.5V is also provided by internal cir-
cuitry at the input stage.
To obtain optimum and trouble free operation please read
operating rules and NSC one-shot application notes careful-
ly and observe recommendations.
Features
Y
Triggered from active-high transition or active-low tran-
sition inputs
Y
Variable pulse width from 30 ns to 28 seconds
Y
Jitter free Schmitt-trigger input
Y
Excellent noise immunity typically 1.2V
Y
Stable pulse width up to 90% duty cycle
Y
TTL, DTL compatible
Y
Compensated for V
CC
and temperature variations
Y
Input clamp diodes
Y
Alternate Military/Aerospace device (54121) is avail-
able. Contact a National Semiconductor Sales Office/
Distributor for specifications.
Functional Description
The basic output pulse width is determined by selection of
an internal resistor R
INT
or an external resistor (R
X
) and
capacitor (C
X
). Once triggered the output pulse width is in-
dependent of further transitions of the inputs and is a func-
tion of the timing components. Pulse width can vary from a
few nano-seconds to 28 seconds by choosing appropriate
R
X
and C
X
combinations. There are three trigger inputs from
the device, two negative edge-triggering (A) inputs, one pos-
itive edge Schmitt-triggering (B) input.
Connection Diagram
Dual-In-Line Package
TL/F/6538–1
Order Number 54121DMQB, 54121FMQB,
DM54121J, DM54121W or DM74121N
See NS Package Number J14A, N14A or W14B
Function Table
Inputs Outputs
A1 A2 B Q Q
LXHL H
XL
XXL L H
HHX
HvH
vHH
vvH
LXu
XL
HeHigh 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
C
1995 National Semiconductor Corporation RRD-B30M105/Printed in U. S. A.