Unit LoadingFan Out

54F74F

Pin Names

Description

UL

HIGHLOW

S

Common Data Select Input

1010

OE

TRI-STATE Output Enable Input (Active LOW)

1010

Data Inputs from Source 0

1010

Data Inputs from Source 1

1010

TRI-STATE Multiplexer Outputs

15040 (333)

b

3 mA24 mA (20 mA)

Functional Description

The ’F257A is a quad 2-input multiplexer with TRI-STATE

outputs It selects four bits of data from two sources under

control of a Common Data Select input When the Select

inputs appears at the outputs in true (non-inverted) form

The device is the logic implementation of a 4-pole 2-posi-

tion switch where the position of the switch is determined by

the logic levels supplied to the Select input The logic equa-

tion for the outputs is shown below

When the Output Enable input (OE) is HIGH the outputs are

forced to a high impedance OFF state If the outputs are

tied together all but one device must be in the high imped-

ance state to avoid high currents that would exceed the

maximum ratings Designers should ensure the Output En-

able signals to TRI-STATE devices whose outputs are tied

together are designed so there is no overlap

Truth Table

Output

Select

Data

Output

Enable

Input

Inputs

OE

Z

HX

X

X

Z

LH

X

L

L

LH

X

H

H

LL

L

X

L

LL

H

X

H

Logic Diagram

TLF9507 – 4

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

2