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 I
0
I
1
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
V
CC
Supply Voltage 54
74
4.5
4.75
5.0
5.0
5.5
5.25
V
T
A
Operating Ambient Temperature Range 54
74
–55
0
25
25
125
70
°C
I
OH
Output Current — High 54, 74 –0.4 mA
I
OL
Output Current — Low 54
74
4.0
8.0
mA
