Dual retriggerable precision monostable multivibrator, 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.

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