5-274

FAST AND LS TTL DATA

SN54/74LS158

FUNCTIONAL DESCRIPTION

The LS158 is a Quad 2-input Multiplexer fabricated with the

Schottky barrier diode process for high speed. It selects four

bits of data from two sources under the control of a common

Select Input (S) and presents the data in inverted form at the

four outputs. The Enable Input (E) is active LOW. When E is

HIGH, all of the outputs (Z) are forced HIGH regardless of all

other inputs.

The LS158 is the logic implementation of a 4-pole,

2-position switch where the position of the switch is deter-

mined by the logic levels supplied to the Select Input.

A common use of the LS158 is the moving of data from two

groups of registers to four common output busses. The

particular register from which the data comes is determined by

the state of the Select Input. A less obvious use is as a function

generator. The LS158 can generate four functions of two

variables with one variable common. This is useful for

implementing gating functions.

TRUTH TABLE

ENABLE

SELECT

INPUT

INPUTS

OUTPUT

E

S

I0

I1

Z

H

X

X

X

H

L

L

L

X

H

L

L

H

X

L

L

H

X

L

H

L

H

X

H

L

H = HIGH Voltage Level

L = LOW Voltage Level

X = Don’t Care

GUARANTEED OPERATING RANGES

Symbol

Parameter

Min

Typ

Max

Unit

VCC

Supply Voltage

54

74

4.5

4.75

5.0

5.0

5.5

5.25

V

TA

Operating Ambient Temperature Range

54

74

– 55

0

25

25

125

70

°C

IOH

Output Current — High

54, 74

– 0.4

mA

IOL

Output Current — Low

54

74

4.0

8.0

mA