1.

General description

The 74HC138; 74HCT138 is a high-speed Si-gate CMOS device and is pin compatible

with Low-power Schottky TTL (LSTTL).

The 74HC138; 74HCT138 decoder accepts three binary weighted address inputs (A0, A1

and A3) and when enabled, provides 8 mutually exclusive active LOW outputs (Y0to Y7).

The 74HC138; 74HCT138 features three enable inputs: two active LOW (E1 and E2) and

one active HIGH (E3). Every output is HIGH unless E1 and E2 are LOW and E3 is HIGH.

This multiple enable function allows easy parallel expansion of the 74HC138; 74HCT138

to a 1-of-32 (5 lines to 32 lines) decoder with just four 74HC138; 74HCT138 ICs and one

inverter.

The 74HC138; 74HCT138 can be used as an eight output demultiplexer by using one of

the active LOW enable inputs as the data input and the remaining enable inputs as

strobes. Permanently tie unused enable inputs to their appropriate active HIGH- or

LOW-state.

The 74HC138; 74HCT138 is identical to the 74HC238; 74HCT238 but has inverting

outputs.

2.

Features and benefits

−40 °Cto+85 °C and from −40 °Cto+125 °C

74HC138; 74HCT138

3-to-8 line decoder/demultiplexer; inverting

Rev. 4 — 27 June 2012

Product data sheet