1. General description
The HEF4538B is a dual retriggerable-resettable monostable multivibrator. Each multivibrator has
an active LOW trigger/retrigger input (nA), an active HIGH trigger/retrigger input (nB), an overriding
active LOW direct reset input (nCD), an output (nQ) and its complement (nQ), and two pins
(nREXT/CEXT, and nCEXT, always connected to ground) for connecting the external timing
components CEXT and REXT. Typical pulse width variation over the specified temperature range is
±0.2 %.
The multivibrator may be triggered by either the positive or the negative edges of the input pulse
and will produce an accurate output pulse with a pulse width range of 10 μs to infinity. 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 REXT × CEXT. The linear design techniques in
LOCMOS (Local Oxide CMOS) guarantee precise control of the output pulse width. A LOW level at
nCD terminates the output pulse immediately. The trigger inputs’ Schmitt trigger action makes the
circuit highly tolerant of slower rise and fall times.
It operates over a recommended VDD power supply range of 3 V to 15 V referenced to VSS (usually
ground). Unused inputs must be connected to VDD, VSS, or another input.
2. Features and benefits
• Tolerant of slow trigger rise and fall times
• Wide supply voltage range from 3.0 V to 15.0 V
• CMOS low power dissipation
• High noise immunity
• Fully static operation
• 5 V, 10 V, and 15 V parametric ratings
• Standardized symmetrical output characteristics
• Complies with JEDEC standard JESD 13-B
• ESD protection:
• HBM JESD22-A114F exceeds 2000 V
• MM JESD22-A115-B exceeds 200 V
• Specified from -40 °C to +85 °C and -40 °C to +125 °C