54121 Datasheet, PDF (1/6 Pages) National Semiconductor (TI) – 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 VCC 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
A1
A2
B
L
X
H
X
L
H
X
X
L
H
H
X
H
v
H
v
H
H
v
v
H
L
X
u
X
L
u
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
L
H
C1995 National Semiconductor Corporation TL F 6538
RRD-B30M105 Printed in U S A