1.

General description

The 74HC4538; 74HCT4538 is a dual retriggerable-resettable monostable multivibrator.

Each multivibrator has two trigger/retrigger inputs (nA and nB), a direct reset input (nCD),

two complementary outputs (nQ and nQ), and two pins (nREXT/CEXT and nCEXT) for

connecting the external timing components CEXT and REXT. Typical pulse width variation

over temperature range is ± 0.2%. The device 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 CEXT and REXT. The output pulse width (T)

is equal to 0.7

 R

EXT  CEXT. The linear design techniques guarantee precise control of

the output pulse width. A LOW level at nCD terminates the output pulse immediately.

Schmitt-trigger action in the trigger inputs makes the circuit highly tolerant to slower rise

and fall times. Inputs include clamp diodes. This enables the use of current limiting

resistors to interface inputs to voltages in excess of VCC.

2.

Features and benefits

 Tolerant of slow trigger rise and fall times

 Separate reset inputs

 Triggering from falling or rising edge

 Complies with JEDEC standard no. 7A

 Input levels:

 For 74HC4538: CMOS level

 For 74HCT4538: TTL level

 ESD protection:

 HBM JESD22-A114F exceeds 2000 V

 MM JESD22-A115-A exceeds 200 V

 Multiple package options

 Specified from

40 Cto+85 C and from 40 Cto+125 C

74HC4538; 74HCT4538

Dual retriggerable precision monostable multivibrator

Rev. 4 — 24 February 2016

Product data sheet