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 C
EXT
and R
EXT
. 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 C
EXT
and R
EXT
. The output
pulse width (T
W
) is equal to 0.7 × R
EXT
× C
EXT
. 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 V
CC
.
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
