Functional Description

The LVQ138 high-speed 1-of-8 decoder/demultiplexer ac-

cepts three binary weighted inputs (A

enabled, provides eight mutually exclusive active-LOW out-

puts (O

active-LOW (E

will be HIGH unless E

This multiple enable function allows easy parallel expansion

of the device to a 1-of-32 (5 lines to 32 lines) decoder with

just four LVQ138 devices and one inverter (see

Figure 1).

The LVQ138 can be used as an 8-output demultiplexer by

using one of the active LOW Enable inputs as the data input

and the other Enable inputs as strobes. The Enable inputs

which are not used must be permanently tied to their appro-

priate active-HIGH or active-LOW state.

Truth Table

Inputs

Outputs

E

1

E

2

E

3

A

0

A

1

A

2

O

0

O

1

O

2

O

3

O

4

O

5

O

6

O

7

H

XXXXX

HHHHHHHH

X

H

XXXX

HHHHHHHH

X

X

L

X

X

X

HHHHHHHH

LL

H

LLLL

HHHHHHH

L

L

HH

L

L

H

L

HHHHHH

L

L

H

L

H

L

HH

L

HHHHH

L

L

HHH

L

HHH

L

HHHH

L

L

H

L

L

HHHHH

L

HHH

L

L

HH

L

HHHHHH

L

H

H

L

L

H

L

HHHHHHHH

L

H

L

L

HHHHHHHHHHH

L

H = HIGH Voltage Level

L = LOW Voltage Level

X = Immaterial

Logic Diagram

DS011350-5

Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.

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