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54121 DM54121 DM74121 One-Shot with Clear and Complementary Outputs
June 1989
54121 DM54121 DM74121 One-Shot with
Clear and Complementary Outputs
Y Jitter free Schmitt-trigger input
General Description Y Excellent noise immunity typically 1 2V
The DM54 74121 is a monostable multivibrator featuring Y Stable pulse width up to 90% duty cycle
both positive and negative edge triggering with complemen-
tary outputs An internal 2kX timing resistor is provided for
Y TTL DTL compatible
design convenience minimizing component count and lay- Y Compensated for VCC and temperature variations
out problems This device can be used with a single external Y Input clamp diodes
capacitor Inputs (A) are active-low trigger transition inputs Y Alternate Military Aerospace device (54121) is avail-
and input (B) is an active-high transition Schmitt-trigger in- able Contact a National Semiconductor Sales Office
put that allows jitter-free triggering from inputs with tran- Distributor for specifications
sition rates as slow as 1 volt second A high immunity to
VCC noise of typically 1 5V is also provided by internal cir- Functional Description
cuitry at the input stage
The basic output pulse width is determined by selection of
To obtain optimum and trouble free operation please read an internal resistor RINT or an external resistor (RX) and
operating rules and NSC one-shot application notes careful- capacitor (CX) Once triggered the output pulse width is in-
ly and observe recommendations dependent of further transitions of the inputs and is a func-
tion of the timing components Pulse width can vary from a
Features few nano-seconds to 28 seconds by choosing appropriate
Y Triggered from active-high transition or active-low tran- RX and CX combinations There are three trigger inputs from
sition inputs the device two negative edge-triggering (A) inputs one pos-
Y Variable pulse width from 30 ns to 28 seconds itive edge Schmitt-triggering (B) input
Connection Diagram Function Table
Inputs Outputs
Dual-In-Line Package
A1 A2 B Q Q
L X H L H
X L H L H
X X L L H
H H X L H
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
TL F 6538