S E M I C O N D U C T O R
CD74HC123, CD74HCT123,
CD74HC423, CD74HCT423
High Speed CMOS Logic Dual Retriggerable
Monostable Multivibrators with Resets
Description
The Harris CD74HC123, CD74HCT123, CD74HC423 and
CD74HCT423 are dual monostable multivibrators with
resets. They are all retriggerable and differ only in that the
123 types can be triggered by a negative to positive reset
pulse; whereas the 423 types do not have this feature. An
external resistor (R
X
) and an external capacitor (C
X
) control
the timing and the accuracy for the circuit. Adjustment of Rx
and C
X
provides a wide range of output pulse widths from
the Q and Q terminals. Pulse triggering on the A and B
inputs occur at a particular voltage level and is not related to
the rise and fall times of the trigger pulses.
Once triggered, the output pulse width may be extended by
retriggering inputs A and B. The output pulse can be
terminated by a LOW level on the Reset (R) pin. Trailing
edge triggering (A) and leading edge triggering (B) inputs
are provided for triggering from either edge of the input
pulse. If either Mono is not used each input on the unused
device (A, B, and R) must be terminated high or low.
The minimum value of external resistance, Rx is typically 5kΩ.
The minimum value external capacitance, C
X
, is 0pF. The
calculation for the pulse width is t
W
= 0.45 R
X
C
X
at V
CC
= 5V.
September 1997
Features
• Overriding Reset Terminates Output Pulse
• Triggering From the Leading or Trailing Edge
• Q and Q Buffered Outputs
• Separate Resets
• Wide Range of Output-Pulse Widths
• Schmitt Trigger on Both A and B Inputs
• Fanout (Over Temperature Range)
- Standard Outputs . . . . . . . . . . . . . . . 10 LSTTL Loads
- Bus Driver Outputs . . . . . . . . . . . . . 15 LSTTL Loads
• Wide Operating Temperature Range . . . -55
o
C to 125
o
C
• Balanced Propagation Delay and Transition Times
• Significant Power Reduction Compared to LSTTL
Logic ICs
• HC Types
- 2V to 6V Operation
- High Noise Immunity: N
IL
= 30%, N
IH
= 30%of V
CC
at
V
CC
= 5V
• HCT Types
- 4.5V to 5.5V Operation
- Direct LSTTL Input Logic Compatibility,
V
IL
= 0.8V (Max), V
IH
= 2V (Min)
- CMOS Input Compatibility, I
l
≤
1µA at V
OL
, V
OH
Ordering Information
PART NUMBER
CD74HC123E
CD74HCT123E
TEMP. RANGE (
o
C)
-55 to 125
-55 to 125
-55 to 125
-55 to 125
-55 to 125
-55 to 125
-55 to 125
-55 to 125
PACKAGE
16 Ld PDIP
16 Ld PDIP
16 Ld PDIP
16 Ld PDIP
16 Ld SOIC
16 Ld SOIC
16 Ld SOIC
16 Ld SOIC
PKG.
NO.
E16.3
E16.3
E16.3
E16.3
M16.15
M16.15
M16.15
M16.15
Pinout
CD74HC123, CD74HCT123, CD74HC423, CD74HCT423
(PDIP, SOIC)
TOP VIEW
1A 1
1B 2
1R 3
1Q 4
2Q 5
2C
X
6
2R
X
C
X
7
GND 8
16 V
CC
15 1R
X
C
X
14 1C
X
13 1Q
12 2Q
11 2R
10 2B
9 2A
CD74HC423E
CD74HCT423E
CD74HC123M
CD74HCT123M
CD74HC423M
CD74HCT423M
NOTES:
1. When ordering, use the entire part number. Add the suffix 96 to
obtain the variant in the tape and reel.
2. Wafer or die for this part number is available which meets all elec-
trical specifications. Please contact your local sales office or
Harris customer service for ordering information.
CAUTION: These devices are sensitive to electrostatic discharge. Users should follow proper IC Handling Procedures.
Copyright
©
Harris Corporation 1997
File Number
1708.1
1
HARRIS [ HARRIS CORPORATION ]
