HD74AC139/HD74ACT139

3

Logic Diagram

Please note that this diagram is provided only for the understanding of logic operations and should not be

used to estimate propagation delays.

Functional Description

The HD74AC139/HD74ACT139 is a high-speed dual 1-of-4 decoder/demultiplexer. The device has two

independent decoders, each of which accepts two binary weighted inputs (A

mutually exclusive active-Low outputs (

O

High all outputs are forced High. The enable can be used as the data input for a 4-output demultiplexer

application. Each half of the HD74AC139/HD74ACT139 generates all four minterms of two variables.

These four minterms are useful in some applications, replacing multiple gate functions as shown in Figure

a, and thereby reducing the number of packages required in a logic network.

Truth Table

Inputs

Outputs

E

A

0

A

1

O

0

O

1

O

2

O

3

H

X

X

HHH

H

LL

L

L

H

H

H

LH

L

H

L

H

H

L

L

H

HHL

H

L

H

H

HHH

L

H :

High Voltage Level

L

:

Low Voltage Level

X :

Immaterial