Philips 74hc hct423 DATASHEETS

INTEGRATED CIRCUITS

DATA SH EET

For a complete data sheet, please also download:

•The IC06 74HC/HCT/HCU/HCMOS Logic Family Specifications

•The IC06 74HC/HCT/HCU/HCMOS Logic Package Information

•The IC06 74HC/HCT/HCU/HCMOS Logic Package Outlines

74HC/HCT423

Dual retriggerable monostable
multivibrator with reset

Product specification
Supersedes data of December 1990
File under Integrated Circuits, IC06

1998 Jul 08

Philips Semiconductors Product specification

Dual retriggerable monostable
multivibrator with reset

FEATURES

• 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

• Output capability: standard (except for nR

EXT/CEXT

• ICC category: MSI

GENERAL DESCRIPTION

The 74HC/HCT423 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 74HC/HCT423 are dual retriggerable monostable
multivibrators with output pulse width control by two
methods. The basic pulse time is programmed by
selection of an external resistor (R

) and capacitor

EXT

QUICK REFERENCE DATA

GND = 0 V; T

= 25 °C; tr= tf= 6 ns

amb

)

74HC/HCT423

(C

). The external resistor and capacitor are normally

EXT

connected as shown in Fig.6.
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.
When nRDis LOW, it forces the nQ output LOW, the
nQ output HIGH and also inhibits the triggering.

Figures 7 and 8 illustrate pulse control by reset. The basic
output pulse width is essentially determined by the values
of the external timing components R
For pulse widths, when C
When C

> 10 000 pF, the typical output pulse width is

EXT

< 10 000 pF, see Fig.9.

EXT

defined as:
tW= 0.45 × R

EXT

× C

EXT

(typ.),

where, tW= pulse width in ns;

R

= external resistor in kΩ;

EXT

C

= external capacitor in pF.

EXT

Schmitt-trigger action in the nA and nB inputs, makes the
circuit highly tolerant to slower input rise and fall times.

The “423” is identical to the “123” but cannot be triggered
via the reset input.

EXT

and C

EXT

.

SYMBOL PARAMETER CONDITIONS

t

/ t

PHL

PLH

C

I

t

W

propagation delay CL= 15 pF; VCC= 5 V;

R

=5 kΩ; C

n

A, nB to nQ, nQ2526ns

n

R

to nQ, nQ2022ns

D

EXT

input capacitance 3.5 3.5 pF
minimum output pulse width nQ, nQ notes 1 and 2 75 75 ns

Notes

1. C

is used to determine the dynamic power dissipation (PDin µW):

PD

PD= CPD× V

2

× fi+∑(CL× V

CC

2

× fo) + 0.75 × C

CC

EXT

× V

CC

2

fi= input frequency in MHz
fo= output frequency in MHz
D = duty factor in %
∑ (CL× V

2

× fo) = sum of outputs

CC

CL= output load capacitance in pF
VCC= supply voltage in V
C

= timing capacitance in pF

EXT

2. For HC the condition is VI= GND to V

CC

For HCT the condition is VI= GND to VCC− 1.5 V

TYPICAL

HC HCT

= 0 pF

EXT

× fo+ D × 16 × VCCwhere:

UNIT

1998 Jul 08 2

Philips Semiconductors Product specification

Dual retriggerable monostable
multivibrator with reset

ORDERING INFORMATION

TYPE

NUMBER

74HC423N;
74HCT423N

74HC423D;
74HCT423D

PIN DESCRIPTION

PIN NO. SYMBOL NAME AND FUNCTION

1, 9 1
2, 10 1B, 2B trigger inputs (positive-edge triggered)
3, 11 1
4, 12 1
72R
8 GND ground (0 V)
13, 5 1Q, 2Q outputs (active HIGH)
14, 6 1C
15 1R
16 V

NAME DESCRIPTION VERSION

DIP16 plastic dual in-line package; 16 leads (300 mil); long body SOT38-1

SO16 plastic small outline package; 16 leads; body width 3.9 mm;

low stand-off height

A, 2A trigger inputs (negative-edge triggered)

RD,2R

D

Q, 2Q outputs (active LOW)

EXT/CEXT

,2C

EXT
EXT/CEXT

CC

EXT

direct reset action (active LOW)

external resistor/capacitor connection

external capacitor connection
external resistor/capacitor connection
positive supply voltage

PACKAGE

74HC/HCT423

SOT109-1

Fig.1 Pin configuration. Fig.2 Fig.3 IEC logic symbol.

1998 Jul 08 3

Philips Semiconductors Product specification

Dual retriggerable monostable
multivibrator with reset

74HC/HCT423

FUNCTION TABLE

n

R

D

LXX L H
XHXL
XXLL
HL↑
H↓H

Notes

1. H = HIGH voltage level
L = LOW voltage level
X = don’t care

↑ = LOW-to-HIGH transition
↓ = HIGH-to-LOW transition

= one HIGH level output pulse

= one LOW level output pulse

Fig.4 Functional diagram.

INPUTS OUTPUTS

nAnB nQ nQ

(2)
(2)

(2)

H

(2)

H

2. If the monostable was triggered before this condition was established, the pulse will continue as programmed.

1998 Jul 08 4

Philips Semiconductors Product specification

Dual retriggerable monostable
multivibrator with reset

74HC/HCT423

It is recommended to ground pins 6 (2C

) externally to pin 8 (GND).

(1C

EXT

) and 14

EXT

Fig.5 Logic diagram.

Fig.6 Timing component connections.

1998 Jul 08 5