DM74121 Datasheet, PDF (1/5 Pages) Fairchild Semiconductor – One-Shot with Clear and Complementary Outputs

June 1989
Revised November 1999
DM74121
One-Shot with Clear and Complementary Outputs
General Description
The DM74121 is a monostable multivibrator featuring both
positive and negative edge triggering with complementary
outputs. An internal 2kΩ timing resistor is provided for
design convenience minimizing component count and lay-
out problems. this device can be used with a single exter-
nal capacitor. Inputs (A) are active-LOW trigger transition
inputs and input (B) is and active-HIGH transition Schmitt-
trigger input that allows jitter-free triggering from inputs with
transition rates as slow as 1 volt/second. A high immunity
to V_CC noise of typically 1.5V is also provided by internal
circuitry at the input stage.
To obtain optimum and trouble free operation please read
operating rules and one-shot application notes carefully
and observe recommendations.
Features
s Triggered from active-HIGH transition or active-LOW
transition inputs
s Variable pulse width from 30 ns to 28 seconds
s Jitter free Schmitt-trigger input
s Excellent noise immunity typically 1.2V
s Stable pulse width up to 90% duty cycle
s TTL, DTL compatible
s Compensated for V_CC and temperature variations
s Input clamp diodes
Ordering Code:
Order Number Package Number
Package Description
DM74121N
N14A
14-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Connection Diagram
Function Table
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
independent of further transitions of the inputs and is func-
tion of the timing components. Pulse width can vary from a
Inputs
A1
A2
L
X
X
L
X
X
H
H
H
↓
↓
H
↓
↓
L
X
X
L
H = HIGH Logic Level
L = LOW Logic Level
 X = Can Be Either LOW or HIGH
= A Positive Pulse
= A Negative Pulse
Outputs
B
Q
Q
H
L
H
H
L
H
L
L
H
X
H
H
H
↑
↑
^L
H
↑ = Positive Going Transition
↓ = Negative Going Transition
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 positive edge Schmitt-triggering (B) input.
© 1999 Fairchild Semiconductor Corporation DS006538
www.fairchildsemi.com