Philips 74HCT423U, 74HCT423PW, 74HCT423N, 74HCT423DB, 74HCT423D Datasheet

INTEGRATED CIRCUITS

DATA SHEET

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

1998 Jul 08

Supersedes data of December 1990

File under Integrated Circuits, IC06

Philips Semiconductors	Product specification

Dual retriggerable monostable

74HC/HCT423

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 nREXT/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 (REXT) and capacitor

QUICK REFERENCE DATA

GND = 0 V; Tamb = 25 °C; tr = tf = 6 ns

(CEXT). The external resistor and capacitor are normally 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 nRD is 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 REXT and CEXT.

For pulse widths, when CEXT < 10 000 pF, see Fig.9. When CEXT > 10 000 pF, the typical output pulse width is defined as:

tW = 0.45 ´ REXT ´ CEXT (typ.), where, tW = pulse width in ns;

REXT = external resistor in kW; CEXT = external capacitor in pF.

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.

SYMBOL

PARAMETER

CONDITIONS

TYPICAL

UNIT

HC

HCT

tPHL/ tPLH

propagation delay

CL = 15 pF; VCC = 5 V;

REXT = 5 kW; CEXT = 0 pF

25

26

ns

nA,

nB to nQ, nQ

nR

D to nQ, nQ

20

22

ns

CI

input capacitance

3.5

3.5

pF

tW

minimum output pulse width nQ, nQ

notes 1 and 2

75

75

ns

Notes

1. CPD is used to determine the dynamic power dissipation (PD in mW):

PD = CPD ´ VCC2 ´ fi + å (CL ´ VCC2 ´ fo) + 0.75 ´ CEXT ´ VCC2 ´ fo + D ´ 16 ´ VCC where:

fi = input frequency in MHz

fo = output frequency in MHz

D = duty factor in %

å (CL ´ VCC2 ´ fo) = sum of outputs

CL = output load capacitance in pF

VCC = supply voltage in V

CEXT = timing capacitance in pF

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

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

1998 Jul 08

2

Philips Semiconductors	Product specification

Dual retriggerable monostable

74HC/HCT423

multivibrator with reset

ORDERING INFORMATION

TYPE

PACKAGE

NUMBER

NAME

DESCRIPTION

VERSION

74HC423N;

DIP16

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

SOT38-1

74HCT423N

74HC423D;

SO16

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

SOT109-1

74HCT423D

low stand-off height

PIN DESCRIPTION

PIN NO.

SYMBOL

NAME AND FUNCTION

1, 9

trigger inputs (negative-edge triggered)

1A,

2A

2, 10

1B, 2B

trigger inputs (positive-edge triggered)

3, 11

direct reset action (active LOW)

1R

D, 2R

D

4, 12

outputs (active LOW)

1Q,

2Q

7

2REXT/CEXT

external resistor/capacitor connection

8

GND

ground (0 V)

13, 5

1Q, 2Q

outputs (active HIGH)

14, 6

1CEXT, 2CEXT

external capacitor connection

15

1REXT/CEXT

external resistor/capacitor connection

16

VCC

positive supply voltage

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

1998 Jul 08

3

Philips Semiconductors	Product specification

Dual retriggerable monostable

74HC/HCT423

multivibrator with reset

Fig.4

Functional diagram.

FUNCTION TABLE

INPUTS

OUTPUTS

nR

D

nA

nB

nQ

nQ

L

X

X

L

H

X

H

X

L(2)

H(2)

X

X

L

L(2)

H(2)

H

L

−

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

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

74HC/HCT423

multivibrator with reset

It is recommended to ground pins 6 (2CEXT) and 14 (1CEXT) externally to pin 8 (GND).

Fig.5 Logic diagram.

Fig.6	Timing component connections.
1998 Jul 08	5