2000 Fairchild Semiconductor Corporation
DS006482
www.fairchildsemi.com
August 1986
Revised May 2000
DM74S257 3-
ST
A
T
E Q
u
a
d
1-
of-
2
Dat
a
Select
or/
M
ult
i
pl
exer
DM74S257
3-STATE Quad 1-of-2 Data Selector/Multiplexer
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 S157, S158, with same pin-outs
s
Schottky-clamped for significant improvement in
A-C performance
s
Provides bus interface from multiple sources in high-per-
formance systems
s
Average propagation delay from data input
4.8 ns
s
Typical power dissipation
320 mW
Ordering Code:
Connection Diagram
Function Table
H
=
HIGH Level
L
=
LOW Level
X
=
Don't Care
Z
=
High Impedance (OFF)
Order Number
Package Number
Package Description
DM74S257N
N16E
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Inputs
Output
Output
Select
A
B
Y
Control
H
X
X
X
Z
L
L
L
X
L
L
L
H
X
H
L
H
X
L
L
L
H
X
H
H
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74S257
Logic Diagram
3
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DM74S257
Absolute Maximum Ratings
(Note 1)
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
Electrical Characteristics
over recommended operating free air temperature (unless otherwise noted)
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.
Supply Voltage
7V
Input Voltage
5.5V
Operating Free Air Temperature Range
0
C to
+
70
C
Storage Temperature Range
-
65
C to
+
150
C
Symbol
Parameter
Min
Nom
Max
Units
V
CC
Supply Voltage
4.75
5
5.25
V
V
IH
HIGH Level Input Voltage
2
V
V
IL
LOW Level Input Voltage
0.8
V
I
OH
HIGH Level Output Current
-
6.5
mA
I
OL
LOW Level Output Current
20
mA
T
A
Free Air Operating Temperature
0
70
C
Symbol
Parameter
Conditions
Min
Typ
Max
Units
(Note 2)
V
I
Input Clamp Voltage
V
CC
=
Min, I
I
=
-
18 mA
-
1.2
V
V
OH
HIGH Level
V
CC
=
Min, I
OH
=
Max
2.4
3.2
V
Output Voltage
V
IL
=
Max, V
IH
=
Min
V
OL
LOW Level
V
CC
=
Min, I
OL
=
Max
0.5
V
Output Voltage
V
IH
=
Min, V
IL
=
Max
I
I
Input Current @ Max Input Voltage
V
CC
=
Max, V
I
=
5.5V
1
mA
I
IH
HIGH Level
V
CC
=
Max
Select
100
A
Input Current
V
I
=
2.7V
Other
50
I
IL
LOW Level
V
CC
=
Max,
Select
-
4
mA
Input Current
V
I
=
0.5V
Other
-
2
I
OZH
Off-State Output Current with
V
CC
=
Max, V
O
=
2.4V
50
A
HIGH Level Output Voltage Applied
V
IH
=
Min, V
IL
=
Max
I
OZL
Off-State Output Current with
V
CC
=
Max, V
O
=
0.5V
-
50
A
LOW Level Output Voltage Applied
V
IH
=
Min, V
IL
=
Max
I
OS
Short Circuit Output Current
V
CC
=
Max (Note 3)
-
40
-
100
mA
I
CCH
Supply Current with Outputs HIGH
V
CC
=
Max (Note 4)
44
68
mA
I
CCL
Supply Current with Outputs LOW
V
CC
=
Max (Note 4)
60
93
mA
I
CCZ
Supply Current with Outputs Disabled
V
CC
=
Max (Note 4)
64
99
mA
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74S257
Switching Characteristics
at V
CC
=
5V and T
A
=
25
C
Note 5: C
L
=
5 pF.
R
L
=
280
Symbol
Parameter
From (Input)
C
L
=
15 pF
C
L
=
50 pF
Units
To (Output)
Min
Max
Min
Max
t
PLH
Propagation Delay Time
Data to Output
7.5
11
ns
LOW-to-HIGH Level Output
t
PHL
Propagation Delay Time
Data to Output
6.5
10
ns
HIGH-to-LOW Level Output
t
PLH
Propagation Delay Time
Select to Output
15
16
ns
LOW-to-HIGH Level Output
t
PHL
Propagation Delay Time
Select to Output
15
16
ns
HIGH-to-LOW Level Output
t
PZH
Output Enable Time
Output Control to Y
19.5
23
ns
to HIGH Level Output
t
PZL
Output Enable Time
Output Control to Y
21
24
ns
to LOW Level Output
t
PHZ
Output Disable Time
Output Control to Y
8.5
ns
to HIGH Level Output (Note 5)
t
PLZ
Output Disable Time
Output Control to Y
14
ns
to LOW Level Output (Note 5)
5
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DM74S257 3-
ST
A
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1-
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2
Dat
a
Select
or/
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Physical Dimensions
inches (millimeters) unless otherwise noted
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.
LIFE SUPPORT POLICY
FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
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
body, or (b) support or sustain life, and (c) whose failure
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.
2. A critical component in any component of a life support
device or system whose failure to perform can be rea-
sonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
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