June 1989
54121/DM54121/DM74121 One-Shot with
Clear and Complementary Outputs
Y
Jitter free Schmitt-trigger input
General Description
Y
Y
Y
Y
Y
Y
Excellent noise immunity typically 1.2V
Stable pulse width up to 90% duty cycle
TTL, DTL compatible
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
Compensated for V
Input clamp diodes
and temperature variations
CC
Alternate Military/Aerospace device (54121) is avail-
able. Contact a National Semiconductor Sales Office/
Distributor for specifications.
V
noise of typically 1.5V is also provided by internal cir-
cuitry at the input stage.
CC
Functional Description
The basic output pulse width is determined by selection of
To obtain optimum and trouble free operation please read
operating rules and NSC one-shot application notes careful-
ly and observe recommendations.
an internal resistor R or an external resistor (R ) and
X
INT
capacitor (C ). Once triggered the output pulse width is in-
X
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
Features
Y
R
and C combinations. There are three trigger inputs from
X
Triggered from active-high transition or active-low tran-
sition inputs
X
the device, two negative edge-triggering (A) inputs, one pos-
itive edge Schmitt-triggering (B) input.
Y
Variable pulse width from 30 ns to 28 seconds
Connection Diagram
Function Table
Inputs
A2
Outputs
Dual-In-Line Package
A1
B
Q
Q
L
X
X
L
H
H
L
H
H
L
X
X
L
L
H
H
H
v
v
L
H
v
H
v
X
X
L
H
H
É
É
É
É
É
ß
ß
ß
ß
ß
H
H
u
u
X
L
e
e
e
e
e
e
e
H
High Logic Level
L
Low Logic Level
X
Can Be Either Low or High
Positive Going Transition
Negative Going Transition
A Positive Pulse
u
v
É
ß
TL/F/6538–1
Order Number 54121DMQB, 54121FMQB,
DM54121J, DM54121W or DM74121N
A Negative Pulse
See NS Package Number J14A, N14A or W14B
C
1995 National Semiconductor Corporation
TL/F/6538
RRD-B30M105/Printed in U. S. A.
NSC [ National Semiconductor ]
