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74HC4538

Dual retriggerable precision monostable multivibrator

Nexperia B.V. All rights reserved 

74HC4538

Dual retriggerable precision monostable multivibrator

Rev. 5 — 17 March 2017

Product data sheet

1 General description

The 74HC4538 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 (TW) is equal to 0.7 × REXT × 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

• CMOS input levels:

• ESD protection:

– HBM JESD22-A114F exceeds 2000 V

– MM JESD22-A115-A exceeds 200 V

• Multiple package options

• Specified from -40 °C to +85 °C and from -40 °C to +125 °C

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