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2-INPUT MULTIPLEXER. SN54LS257B Datasheet |
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QUAD 2-INPUT MULTIPLEXER
WITH 3-STATE OUTPUTS
The LSTTL / MSI SN54 / 74LS257B and the SN54 / 74LS258B are Quad
2-Input Multiplexers with 3-state outputs. Four bits of data from two sources
can be selected using a Common Data Select input. The four outputs present
the selected data in true (non-inverted) form. The outputs may be switched to
a high impedance state with a HIGH on the common Output Enable (EO) In-
put, allowing the outputs to interface directly with bus oriented systems. It is
fabricated with the Schottky barrier diode process for high speed and is com-
pletely compatible with all Motorola TTL families.
• Schottky Process For High Speed
• Multiplexer Expansion By Tying Outputs Together
• Non-Inverting 3-State Outputs
• Input Clamp Diodes Limit High Speed Termination Effects
• Special Circuitry Ensures Glitch Free Multiplexing
• ESD > 3500 Volts
VCC E0
16 15
CONNECTION DIAGRAM DIP (TOP VIEW)
I0c I1c Zc I0d I1d Zd
14 13 12 11 10 9
SN54/74LS257B
VCC = PIN 16
GND = PIN 8
1 2 3 4 56 78
S I0a I1a Za I0b I1b Zb GND
VCC E0 I0c I1c Zc I0d I1d Zd
16 15 14 13 12 11 10 9
SN54/74LS258B
1 2 3 4 56 78
S I0a I1a Za I0b I1b Zb GND
NOTE:
The Flatpak version
has the same pinouts
(Connection Diagram) as
the Dual In-Line Package.
SN54/74LS257B
SN54/74LS258B
QUAD 2-INPUT MULTIPLEXER
WITH 3-STATE OUTPUTS
LOW POWER SCHOTTKY
16
1
16
1
16
1
J SUFFIX
CERAMIC
CASE 620-09
N SUFFIX
PLASTIC
CASE 648-08
D SUFFIX
SOIC
CASE 751B-03
ORDERING INFORMATION
SN54LSXXXJ
SN74LSXXXN
SN74LSXXXD
Ceramic
Plastic
SOIC
FAST AND LS TTL DATA
5-427
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SN54/74LS257B D SN54/74LS258B
LOGIC DIAGRAMS
E0
15
I0a
2
I1a
3
SN54 / 74LS257B
I0b
5
I1b
6
I0c
14
I1c
13
I0d
11
I1d
10
S
1
4
Za
E0
15
I0a
2
I1a
3
7 12
Zb Zc
SN54 / 74LS258B
I0b
5
I1b
6
I0c
14
I1c
13
9
Zd
I0d
11
I1d
10
S
1
VCC = PIN 16
GND = PIN 8
= PIN NUMBERS
4
Za
7 12
Zb Zc
FAST AND LS TTL DATA
5-428
9
Zd
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SN54/74LS257B D SN54/74LS258B
FUNCTIONAL DESCRIPTION
The LS257B and LS258B are Quad 2-Input Multiplexers
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 I0 inputs are selected and
when Select is HIGH, the I1 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.
The LS257B and LS258B are the logic implementation of a
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
Za = E0 • (I1a • S + I0a • S) Zb = E0 • (I1b • S + I0b • S)
Zc = E0 • (I1c • S + I0c • S) Zd = E0 • (I1d • S + I0d • S)
When the Output Enable Input (E0) 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 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
Za = E0 • (I1a • S + I0a • S) Zb = E0 • (I1b • S + I0b • S)
Zc = E0 • (I1c • S + I0c • S) Zd = E0 • (I1d • S + I0d • S)
TRUTH TABLE
OUTPUT SELECT
ENABLE INPUT
EO S
HX
LH
LH
LL
LL
H = HIGH Voltage Level
L = LOW Voltage Level
X = Don’t Care
(Z) = High Impedance (off)
DATA OUTPUTS OUTPUTS
INPUTS LS257B LS258B
I0 I1
XX
XL
XH
LX
HX
Z
(Z)
L
H
L
H
Z
(Z)
H
L
H
L
GUARANTEED OPERATING RANGES
Symbol
Parameter
VCC
Supply Voltage
TA Operating Ambient Temperature Range
IOH Output Current — High
IOL Output Current — Low
Min Typ Max Unit
54 4.5 5.0 5.5
74 4.75 5.0 5.25
V
54 – 55 25 125 °C
74 0 25 70
54
– 1.0
mA
74 – 2.6
54 12 mA
74 24
FAST AND LS TTL DATA
5-429
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