74HCSLASHHCT4538 datasheet(2/13 Pages) PHILIPS

2 / 13 page

September 1993

Philips Semiconductors

Product speciﬁcation

Dual retriggerable precision monostable

multivibrator

74HC/HCT4538

FEATURES

• Separate reset inputs

• Triggering from leading or trailing edge

• Output capability: standard

• ICC category: MSI

• Power-on reset on-chip

GENERAL DESCRIPTION

The 74HC/HCT4538 are high-speed Si-gate CMOS

devices and are pin compatible with “4538” of the “4000B”

series. They are specified in compliance with JEDEC

standard no. 7A.

The 74HC/HCT4538 are dual retriggerable-resettable

monostable multivibrators. Each multivibrator has an

active LOW trigger/retrigger input (nA0), an active HIGH

trigger/retrigger input (nA1) , an overriding active LOW

direct reset input (nRD), an output (nQ) and its complement

(nQ), and two pins (nCTC and nRCTC) for connecting the

external timing components Ct and Rt. Typical pulse width

variation over temperature range is

± 0.2%.

The “4538” may be triggered by either the positive or the

negative edges of the input pulse. The duration and

accuracy of the output pulse are determined by the

external timing components Ct and Rt. The output pulse

width (T) is equal to 0.7

× Rt × Ct. The linear design

techniques guarantee precise control of the output pulse

width.

A LOW level at nRD terminates the output pulse

immediately.

Schmitt-trigger action in the trigger inputs makes the circuit

highly tolerant to slower rise and fall times.

QUICK REFERENCE DATA

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

Notes

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

PD = CPD × VCC2 × fi +∑ (CL × VCC2 × fo) +

+ 0.48 × CEXT × VCC2 × fo + D × 0.8 × VCC where:

fi = input frequency in MHz

fo = output frequency in MHz

∑ (CL × VCC2 × fo) = sum of outputs

CL = output load capacitance in pF

VCC = supply voltage in V

D = duty factor in %

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

ORDERING INFORMATION

See

“74HC/HCT/HCU/HCMOS Logic Package Information”.

SYMBOL

PARAMETER

CONDITIONS

TYPICAL

UNIT

HCT

tPHL/ tPLH

propagation delay nA0,nA1 to nQ, nQCL = 15 pF; VCC = 5 V

input capacitance

3.5

CPD

power dissipation capacitance per multivibrator

notes 1 and 2

136

138

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