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2

Functional Description

The AC/ACT253 contains two identical 4-input multiplexers

with 3-STATE outputs. They select two bits from four

impedance (High Z) state. This device is the logic imple-

mentation of a 2-pole, 4-position switch, where the position

of the switch is determined by the logic levels supplied to

the two select inputs. The logic equations for the outputs

are shown:

If the outputs of 3-STATE devices are tied together, all but

one device must be in the high impedance state to avoid

high currents that would exceed the maximum ratings.

Designers should ensure that Output Enable signals to 3-

STATE devices whose outputs are tied together are

designed so that there is no overlap.

Truth Table

H

= HIGH Voltage Level

L

= LOW Voltage Level

X

= Immaterial

Z

= High Impedance

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.

Select

Data Inputs

Output

Outputs

Inputs

Enable

OE

Z

X

X

X

XXX

H

Z

L

L

L

XXX

L

L

L

L

H

XXX

L

H

HL

X

L

X

X

L

L

HL

X

H

X

X

L

H

LH

X

X

L

X

L

L

LH

X

X

H

X

L

H

HH

X

X

X

L

L

L

HH

X

X

X

H

L

H