54122 DM74122 Retriggerable Resettable Multivibrator
June 1989
54122 DM74122
Retriggerable Resettable Multivibrator
General Description
The 鈥?22 features positive and negative DC level triggering
inputs complementary outputs an optional 10 kX internal
timing resistor and an overriding Direct Clear (C
D
) input
When the circuit is in the quasi-stable (delay) state another
trigger applied to the inputs (per Truth Table) will cause the
delay period to start again without disturbing the outputs
This process can be repeated indefinitely and thus the out-
put pulse period (Q HIGH Q LOW) can be made as long as
desired Alternatively a delay period can be terminated
by a LOW signal applied to C
D
which also prevents trigger-
ing An internal connection from C
D
to the input gate makes
it possible to trigger the circuit by a positive-going signal on
C
D
as shown in the Truth Table For timing capacitor values
greater than 1000 pF the output pulse width is defined as
follows
t
w
e
0 32 R
X
C
X
(1 0
a
0 7 R
X
)
Where t
w
is in ns R
X
is in kX and C
X
is in pF
Connection Diagram
Dual-In-Line Package
Logic Symbol
TL F 10212 鈥?2
TL F 10212 鈥?1
Order Number 54122DMQB 54122FMQB or DM74122N
See NS Package Number J14A N14A or W14B
V
CC
e
Pin 14
GND
e
Pin 7
NC
e
Pins 10 and 12
Pin Names
A
1
A
2
B
1
B
2
C
D
Q Q
Description
Trigger Inputs (Active Falling Edge)
Trigger Inputs (Active Rising Edge)
Direct Clear Inputs (Active LOW)
Outputs
C
1995 National Semiconductor Corporation
TL F 10212
RRD-B30M105 Printed in U S A