DM74LS257B 3-STATE Quad 2-Data Selectors/Multiplexers
June 1989
Revised November 1999
DM74LS257B
3-STATE Quad 2-Data Selectors/Multiplexers
General Description
These Schottky-clamped high-performance multiplexers
feature 3-STATE outputs that can interface directly with
data lines of bus-organized systems. With all but one of the
common outputs disabled (at a high impedance state), the
low impedance of the single enabled output will drive the
bus line to a HIGH or LOW logic level. To minimize the pos-
sibility that two outputs will attempt to take a common bus
to opposite logic levels, the output enable circuitry is
designed such that the output disable times are shorter
than the output enable times.
This 3-STATE output feature means that n-bit (paralleled)
data selectors with up to 258 sources can be implemented
for data buses. It also permits the use of standard TTL reg-
isters for data retention throughout the system.
Features
s
3-STATE versions LS157 and LS158 with same pinouts
s
Schottky-clamped for significant improvement in A-C
performance
s
Provides bus interface from multiple sources in
high-performance systems
s
Average propagation delay from data input 12 ns
s
Typical power dissipation: 50 mW
Ordering Code:
Order Number
DM74LS257BM
DM74LS257BN
Package Number
M16A
N16E
Package Description
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Connection Diagram
Logic Diagram
Function Table
Inputs
Output
Control
H
L
L
L
L
H
=
HIGH Level
L
=
LOW Level
Output Y
A
X
L
H
X
X
B
X
X
X
L
H
LS257
Z
L
H
L
H
Select
X
L
L
H
H
X
=
Don’t Care
Z
=
High Impedance (off)
© 1999 Fairchild Semiconductor Corporation
DS006417
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DM74LS257B
Absolute Maximum Ratings
(Note 1)
Supply Voltage
Input Voltage
Operating Free Air Temperature Range
Storage Temperature Range
7V
7V
0°C to
+70°C
−65°C
to
+150°C
Note 1:
The “Absolute Maximum Ratings” are those values beyond which
the safety of the device cannot be guaranteed. the device should not be
operated at these limits. The parametric values defined in the Electrical
Characteristics tables are not guaranteed at the absolute maximum ratings.
The Recommended Operating Conditions table will define the conditions
for actual device operation.
Recommended Operating Conditions
Symbol
V
CC
V
IH
V
IL
I
OH
I
OL
T
A
Parameter
Supply Voltage
HIGH Level Input Voltage
LOW Level Input Voltage
HIGH Level Output Current
LOW Level Output Current
Free Air Operating Temperature
0
Min
4.75
2
0.8
−2.6
24
70
Nom
5
Max
5.25
Units
V
V
V
mA
mA
°C
DC Electrical Characteristics
Symbol
V
I
V
OH
V
OL
I
I
I
IH
I
IL
I
OZH
I
OZL
I
OS
I
CCH
I
CCL
I
CCZ
Parameter
Input Clamp Voltage
HIGH Level Output Voltage
LOW Level Output
Voltage
Input Current @ Max
Input Voltage
HIGH Level Input
Current
LOW Level Input
Current
OFF-State Output Current with
HIGH Level Output Voltage Applied
OFF-State Output Current with
LOW Level Output Voltage Applied
Short Circuit Output Current
Supply Current with Outputs HIGH
Supply Current with Outputs LOW
Conditions
V
CC
=
Min, I
I
= −18
mA
V
IL
=
Max, V
IH
=
Min
V
IL
=
Max, V
IH
=
Min
I
OL
=
12 mA, V
CC
=
Min
V
CC
=
Max,
V
I
=
7V
V
CC
=
Max,
V
I
=
2.7V
V
CC
=
Max,
V
I
=
0.4V
V
CC
=
Max, V
O
=
2.7V
V
IH
=
Min, V
IL
=
Max
V
CC
=
Max, V
O
=
0.4V
V
IH
=
Min, V
IL
=
Max
V
CC
=
Max (Note 3)
V
CC
=
Max (Note 4)
V
CC
=
Max (Note 4)
−20
5.9
9.2
12
Select
Other
Select
Other
Select
Other
2.4
3.1
0.35
0.25
0.5
0.4
0.2
0.1
40
20
−0.8
−0.4
20
−20
−100
10
16
19
Min
Typ
(Note 2)
Max
−1.5
Units
V
V
V
mA
µA
mA
µA
µA
mA
mA
mA
mA
Supply Current with Outputs Disabled V
CC
=
Max (Note 4)
Note 2:
All typicals are at V
CC
=
5V, T
A
=
25°C.
Note 3:
Not more than one output should be shorted at a time, and the duration should not exceed one second.
Note 4:
I
CC
is measured with all outputs open and all possible inputs grounded, while achieving the stated output conditions.
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2
DM74LS257B
Switching Characteristics
V
CC
=
5V and T
A
=
25°C
RL
=
667Ω
Symbol
t
PLH
t
PHL
t
PLH
t
PHL
t
PZH
t
PZL
t
PHZ
t
PLZ
Parameter
Propagation Delay Time
LOW-to-HIGH Level Output
Propagation Delay Time
HIGH-to-LOW Level Output
Propagation Delay Time
LOW-to-HIGH Level Output
Propagation Delay Time
HIGH-to-LOW Level Output
Output Enable Time
to HIGH Level Output
Output Enable Time
to LOW Level Output
Output Disable Time from
HIGH Level Output (Note 5)
Output Disable Time from
LOW Level Output (Note 5)
Note 5:
C
L
=
5 pF
From (Input)
To (Output)
Data to Output
Data to Output
Select to Output
Select to Output
Output Control to Y
Output Control to Y
Output Control to Y
Output Control to Y
C
L
=
45 pF
Min
Max
18
18
28
35
15
28
28
25
C
L
=
150 pF
Min
Max
27
27
35
42
27
38
Units
ns
ns
ns
ns
ns
ns
ns
ns
3
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DM74LS257B
Physical Dimensions
inches (millimeters) unless otherwise noted
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
Package Number M16A
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4
DM74LS257B 3-STATE Quad 2-Data Selectors/Multiplexers
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Package Number N16E
Fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and
Fairchild reserves the right at any time without notice to change said circuitry and specifications.
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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD
SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the
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to perform when properly used in accordance with
instructions for use provided in the labeling, can be rea-
sonably expected to result in a significant injury to the
user.
5
2. A critical component in any component of a life support
device or system whose failure to perform can be rea-
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