SN74LS257D Motorola, SN74LS257D Datasheet - Page 3

• Manufacturer Part Number: SN74LS257D
• Description: QUAD 2-INPUT MULTIPLEXER WITH 3-STATE OUTPUTS
• Manufacturer: Motorola

FUNCTIONAL DESCRIPTION
with 3-state outputs. They select four bits of data from two
sources each under control of a Common Data Select Input.
When the Select Input is LOW, the I 0 inputs are selected and
when Select is HIGH, the I 1 inputs are selected. The data on
the selected inputs appears at the outputs in true (non-
inverted) form for the LS257B and in the inverted form for the
LS258B.
4-pole, 2-position switch where the position of the switch is
determined by the logic levels supplied to the Select Input. The
logic equations for the outputs are shown below:
LS257B
Z a = E 0
Z c = E 0
GUARANTEED OPERATING RANGES
V CC
T A
I OH
I OL
The LS257B and LS258B are Quad 2-Input Multiplexers
The LS257B and LS258B are the logic implementation of a
Symbol
(I 1a
(I 1c
Supply Voltage
Operating Ambient Temperature Range
Output Current — High
Output Current — Low
S + I 0c
S + I 0a
S) Z d = E 0
S) Z b = E 0
H = HIGH Voltage Level
L = LOW Voltage Level
X = Don’t Care
(Z) = High Impedance (off)
SN54/74LS257B
Parameter
OUTPUT
ENABLE
E O
H
L
L
L
L
(I 1b
(I 1d
SELECT
S + I 0b
S + I 0d
INPUT
FAST AND LS TTL DATA
S
X
H
H
L
L
TRUTH TABLE
S)
S)
INPUTS
I 0
5-429
X
X
X
H
L
DATA
D
SN54/74LS258B
I 1
H
forced to a high impedance “off” state. If the outputs 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 there is no overlap.
LS258B
Z a = E 0
Z c = E 0
X
L
X
X
When the Output Enable Input (E 0 ) is HIGH, the outputs are
OUTPUTS
54
74
54
74
54
74
54
74
LS257B
(Z)
H
H
Z
L
L
(I 1c
(I 1a
4.75
– 55
Min
OUTPUTS
4.5
0
S + I 0c
S + I 0a
LS258B
(Z)
Z
H
H
L
L
S) Z d = E 0
S) Z b = E 0
Typ
5.0
5.0
25
25
– 1.0
– 2.6
Max
5.25
125
5.5
70
12
24
(I 1d
(I 1b
S + I 0b
S + I 0d
Unit
mA
mA
V
C
S)
S)