描述 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.

特性 Features

? Tolerant of slow trigger rise and fall times
? Fully static operation
? 5 V, 10 V, and 15 V parametric ratings
? Standardized symmetrical output characteristics
? Specified from -40 °C to +85 °C and -40 °C to +125 °C
? Complies with JEDEC standard JESD 13-B