74AHC123 Philips Semiconductors, 74AHC123 Datasheet - Page 2

• Manufacturer Part Number: 74AHC123
• Description: Dual retriggerable monostable multivibrator with reset
• Manufacturer: Philips Semiconductors

Philips Semiconductors
FEATURES
DESCRIPTION
The 74AHC/AHCT123A 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 74AHC/AHCT123A are dual retriggerable monostable
multivibrators with output pulse width control by three
methods. The basic pulse time is programmed by
selection of an external resistor (R
(C
connected as shown in Fig.6.
2000 Mar 15
ESD protection:
HBM EIA/JESD22-A114-A exceeds 2000 V
MM EIA/JESD22-A115-A exceeds 200 V
CDM EIA/JESD22-C101 exceeds 1000 V
All inputs have Schmitt-trigger actions
Inputs accept voltages higher than V
For AHC only: operates with CMOS input levels
For AHCT only: operates with TTL input levels
Specified from 40 to +85 C and 40 to +125 C
DC triggered from active HIGH or active LOW inputs
Retriggerable for very long pulses up to 100% duty
factor
Direct reset terminates output pulse
Output capability: standard (except for nR
EXT
Dual retriggerable monostable multivibrator
with reset
). The external resistor and capacitor are normally
EXT
) and capacitor
CC
EXT
/C
EXT
).
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 nR
triggering.
An internal connection from nR
possible to trigger the circuit by a positive-going signal at
input nR
illustrate pulse control by retriggering and early reset. The
basic output pulse width is essentially determined by the
value of the external timing components R
When C
defined as: t
R
in pF. Schmitt-trigger action at all inputs makes the circuit
highly tolerant to slower input rise and fall times. The ‘123’
is identical to the ‘423’ but can be triggered via the reset
input.
EXT
= external resistor in k ; C
EXT
D
as shown in the function table. Figs 8 and 9
W
10 nF, the typical output pulse width is
= R
EXT
C
EXT
where t
D
to the input gate makes it
EXT
D
74AHCT123A
, which also inhibits the
Product specification
74AHC123A;
W
= external capacitor
= pulse width in ns;
EXT
and C
EXT
.