Unit LoadingFan Out

54F74F

Pin Names

Description

UL

HIGHLOW

Address Inputs

1010

Enable Inputs (Active LOW)

1010

Enable Input (Active HIGH)

1010

Outputs (Active LOW)

50333

b

1 mA20 mA

Functional Description

The ’F138 high-speed 1-of-8 decoderdemultiplexer ac-

enabled provides eight mutually exclusive active LOW out-

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 ’F138 devices and one inverter (See

Figure 1 ) The

’F138 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 appropriate

active HIGH or active LOW state

Truth Table

Inputs

Outputs

H

X

X

X

X

X

HH

H

HHHHH

X

H

X

X

X

X

H

H

H

HHHHH

X

X

L

X

X

X

HH

H

HHHHH

L

L

H

L

L

L

L

H

H

HHHHH

L

L

H

H

L

L

H

L

H

HHHHH

L

L

H

L

H

L

HH

L

HHHHH

L

L

H

H

H

L

HH

H

L

HHHH

L

L

H

L

L

H

HH

H

H

L

HHH

L

L

H

H

L

H

H

H

H

H

HLH

H

L

L

H

L

H

H

HH

H

HHH

L

H

L

L

H

H

H

H

HH

H

HHHH

L

2