Functional Description

? Dual Monostable Multivibrator

General

The 74HC4538FT is a high speed CMOS MONOSTABLE MULTIVIBRATOR fabricated with silicon gate CMOS

technology. It achieves the high speed operation similar to equivalent LSTTL while maintaining the CMOS low

power dissipation.

There are two trigger inputs, A input (positive edge input), and B input (negative edge input). These inputs are

valid for a slow rise/fall time signal (tr = tf = 1 s) as they are schmitt trigger inputs.

After triggering, the output stays in a MONOSTABLE state for the time period determined by the external

resistor and capacitor (RX, CX). A low level at CD input breaks this STABLE STATE. In the MONOSTABLE

state, if a new trigger is applied, it makes the MONOSTABLE period longer (retrigger mode).

Limitations for CX and RX are as follows:

External capacitor CX ........... No limitation

External resistor RX.............. VCC = 2.0 V more than 5 kΩ

VCC ≥ 3.0 V more than 1 kΩ

All inputs are equipped with protection circuits against static discharge or transient excess voltage.

Features (Note)

(1) Wide operating temperature range: Topr = -40 to 125 

(2) High speed: tpd = 25 ns (typ.) at VCC = 5.0 V

(3) Low power dissipation:

Standby state: ICC = 4.0 μA (max) at Ta = 25 

Active state: ICC = 350 μA (max) at Ta = 25 

(4) Balanced propagation delays: tPLH ≈ tPHL

(5) Wide operating voltage range: VCC(opr) = 2.0 to 6.0 V