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74HC123; 74HCT123
Dual retriggerable monostable multivibrator with reset
Rev. 8 -- 16 December 2011 Product data sheet
1. General description
The 74HC123; 74HCT123 are high-speed Si-gate CMOS devices and are pin compatible
with Low-power Schottky TTL (LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The 74HC123; 74HCT123 are dual retriggerable monostable multivibrators with output
pulse width control by three methods:
1. The basic pulse is programmed by selection of an external resistor (REXT) and
capacitor (CEXT).
2. Once triggered, the basic output pulse width may be extended by retriggering the
gated active LOW-going edge input (nA) or the active HIGH-going edge input (nB). By
repeating this process, the output pulse period (nQ = HIGH, nQ = LOW) can be made
as long as desired. Alternatively an output delay can be terminated at any time by a
LOW-going edge on input nRD, which also inhibits the triggering.
3. An internal connection from nRD to the input gates makes it possible to trigger the
circuit by a HIGH-going signal at input nRD as shown in the function table.
Schmitt-trigger action in the nA and nB inputs, makes the circuit highly tolerant to slower
input rise and fall times.
The 74HC123; 74HCT123 are identical to the 74HC423; 74HCT423 but can be triggered
via the reset input.
2. Features and benefits
DC triggered from active HIGH or active LOW inputs
Retriggerable for very long pulses up to 100 % duty factor
Direct reset terminates output pulse
Schmitt-trigger action on all inputs except for the reset input
ESD protection:
HBM JESD22-A114F exceeds 2000 V
MM JESD22-A115-A exceeds 200 V
Specified from 40 C to +85 C and from 40 C to +125 C
NXP Semiconductors 74HC123; 74HCT123
Dual retriggerable monostable multivibrator with reset
3. Ordering information
Table 1. Ordering information
Type number Package
Temperature range Name Description Version
74HC123N 40 C to +125 C DIP16 plastic dual in-line package; 16 leads (300 mil) SOT38-4
74HCT123N
74HC123D 40 C to +125 C SO16 plastic small outline package; 16 leads; SOT109-1
74HCT123D body width 3.9 mm
74HC123DB 40 C to +125 C SSOP16 plastic shrink small outline package; 16 leads; SOT338-1
74HCT123DB body width 5.3 mm
74HC123PW 40 C to +125 C TSSOP16 plastic thin shrink small outline package; 16 leads; SOT403-1
74HCT123PW body width 4.4 mm
74HC123BQ 40 C to +125 C DHVQFN16 plastic dual in-line compatible thermal enhanced SOT763-1
very thin quad flat package; no leads; 16 terminals;
body 2.5 3.5 0.85 mm
4. Functional diagram
14
1CEXT
15
1REXT/CEXT
S
13
Q 1Q
1
1A
T
4
Q 1Q
2
1B
RD
3
1RD 6
2CEXT
7
2REXT/CEXT
S
5
Q 2Q
9
2A
T
12
10 Q 2Q
2B
RD
11
2RD
001aaa610
Fig 1. Functional diagram
74HC_HCT123 All information provided in this document is subject to legal disclaimers.