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
Y
Y
Y
Y
Y
Y
Y
Jitter free Schmitt-trigger input
Excellent noise immunity typically 1 2V
Stable pulse width up to 90% duty cycle
TTL DTL compatible
Compensated for V
CC
and temperature variations
Input clamp diodes
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
Features
Y
Y
Triggered from active-high transition or active-low tran-
sition inputs
Variable pulse width from 30 ns to 28 seconds
Connection Diagram
Dual-In-Line Package
Function Table
Inputs
A1
L
X
X
H
H
A2
X
L
X
H
B
H
H
L
X
H
H
H
Q
L
L
L
L
Outputs
Q
H
H
H
H
v
H
v
v
L
X
H
L
X
TL F 6538 – 1
v
X
L
u
u
e
High Logic Level
e
Low Logic Level
e
Can Be Either Low or High
e
Positive Going Transition
e
Negative Going Transition
e
A Positive Pulse
e
A Negative Pulse
u
v
Order Number 54121DMQB 54121FMQB
DM54121J DM54121W or DM74121N
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 ]
