SL74HC123
Dual Retriggerable Monostable Multivibrator
The SL74HC123 is identical in pinout to the LS/ALS123. The device
inputs are compatible with standard CMOS outputs; with pullup
resistors, they are compatible with LS/ALSTTL outputs.
There are two trigger inputs, A INPUT (negative edge) and
B INPUT (positive edge). These inputs are valid for rising/falling
signals.
The device may also be triggered by using the CLR input (positive-
edge) because of the Schmitt-trigger input; after triggering the output
maintains the MONOSTABLE state for the time period determined by
the external resistor RX and capacitor CX. Taking CLR low breaks this
MONOSTABLE STATE. If the next trigger pulse occurs during the
ORDERING INFORMATION
MONOSTABLE period it makes the MONOSTABLE period longer.
SL74HC123N Plastic
SL74HC123D SOIC
TA = -55° to 125° C for all packages
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Outputs Directly Interface to CMOS, NMOS, and TTL
Operating Voltage Range: 3.0 to 6.0 V
Low Input Current: 1.0 mA
High Noise Immunity Characteristic of CMOS Devices
PIN ASSIGNMENT
LOGIC DIAGRAM
FUNCTION TABLE
PIN 16 =VCC
PIN 8 = GND
Inputs
Outputs
Note
Note
A
B
H
CLR
H
Q
Q
(1) CX, RX, DX are external components.
(2) DX is a clamping diode.
Output
Enable
The external capacitor is charged to V in the stand-by
CC
X
H
L
L
H
H
H
L *
L *
H *
H *
Inhibit
Inhibit
state, i.e. no trigger. When the supply voltage is turned off
CX is discharged mainly through an internal parasitic diode. If
CX is sufficiently large and VCC decreases rapidy, there will be
some possibility of damaging the I.C. with a surge current or
latch-up. If the voltage supply filter capacitor is large enough
and VCC decrease slowly, the surge current is automatically
limited and damage the I.C. is avoided. The maximum forward
current of the parasitic diode is approximately 20 mA.
X
Output
Enable
L
H
X
Output
Enable
X
L
L
H
Inhibit
X = don’t care
* - except for monostable period
System Logic
Semiconductor
SLS
SLS [ SYSTEM LOGIC SEMICONDUCTOR ]
