Revised March 2000
DM74LS251
3-STATE 1-of-8 Line Data Selector/Multiplexer
General Description
Features
These data selectors/multiplexers contain full on-chip
binary decoding to select one-of-eight data sources, and
feature a strobe-controlled 3-STATE output. The strobe
must be at a low logic level to enable these devices. The 3STATE outputs permit direct connection to a common bus.
When the strobe input is HIGH, both outputs are in a highimpedance state in which both the upper and lower transistors of each totem-pole output are OFF, and the output neither drives nor loads the bus significantly. When the strobe
is LOW, the outputs are activated and operate as standard
TTL totem-pole outputs.
■ 3-STATE version of DM74LS151
■ Interface directly with system bus
■ Perform parallel-to-serial conversion
■ Permit multiplexing from N-lines to one line
■ Complementary outputs provide true and inverted data
■ Maximum number of common outputs: 129
■ Typical propagation delay time (D to Y): 17 ns
■ Typical power dissipation: 35 mW
To minimize the possibility that two outputs will attempt to
take a common bus to opposite logic levels, the output control circuitry is designed so that the average output disable
time is shorter than the average output enable time.
Ordering Code:
Order Number
Package Number
Package Description
DM74LS251M
M16A
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
DM74LS251N
N16E
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
Function Table
Inputs
Select
Outputs
Strobe
Y
W
C
B
A
S
X
X
X
H
Z
Z
L
L
L
L
D0
D0
L
L
H
L
D1
D1
L
H
L
L
D2
D2
L
H
H
L
D3
D3
H
L
L
L
D4
D4
H
L
H
L
D5
D5
H
H
L
L
D6
D6
H
H
H
L
D7
D7
H = HIGH Logic Level
L = LOW Logic Level
X = Don't Care
Z = High Impedance (OFF)
D0, D1…D7 = The level of the respective D input
© 2000 Fairchild Semiconductor Corporation
DS006415
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DM74LS251 3-STATE 1-of-8 Line Data Selector/Multiplexer
August 1986
DM74LS251
Logic Diagram
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2
Supply Voltage
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” table are not guaranteed at the absolute maximum ratings.
The “Recommended Operating Conditions” table will define the conditions
for actual device operation.
7V
Input Voltage
7V
0°C to +70°C
Operating Free Air Temperature Range
−65°C to +150°C
Storage Temperature Range
Recommended Operating Conditions
Symbol
Parameter
Min
Nom
Max
4.75
5
5.25
Units
VCC
Supply Voltage
VIH
HIGH Level Input Voltage
V
VIL
LOW Level Input Voltage
0.8
V
IOH
HIGH Level Output Current
−2.6
mA
IOL
LOW Level Output Current
24
mA
TA
Free Air Operating Temperature
70
°C
2
V
0
Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted)
Symbol
Parameter
Conditions
VI
Input Clamp Voltage
VCC = Min, II = −18 mA
VOH
HIGH Level
VCC = Min, IOH = Max
Output Voltage
VIL = Max, VIH = Min
VOL
LOW Level
VCC = Min, IOL = Max
Output Voltage
VIL = Max, VIH = Min
Min
Typ
(Note 2)
Max
−1.5
2.4
IOL = 12 mA, VCC = Min
3.1
Units
V
V
0.35
0.5
0.25
0.4
V
II
Input Current @ Max Input Voltage
VCC = Max, VI = 7V
0.1
IIH
HIGH Level Input Current
VCC = Max, VI = 2.7V
20
µA
IIL
LOW Level Input Current
VCC = Max, VI = 0.4V
−0.4
mA
IOZH
Off-State Output Current with
VCC = Max, VO = 2.7V
HIGH Level Output Voltage Applied
VIH = Min, VIL = Max
20
µA
−20
µA
IOZL
Off-State Output Current with
VCC = Max, VO = 0.4V
LOW Level Output Voltage Applied
VIH = Min, VIL = Max
−20
mA
IOS
Short Circuit Output Current
VCC = Max (Note 3)
−100
mA
ICC1
Supply Current
VCC = Max (Note 4)
6.1
10
mA
ICC2
Supply Current
VCC = Max (Note 5)
7.1
12
mA
Note 2: All typicals are at VCC = 5V, TA = 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: ICC1 is measured with the outputs open, STROBE grounded, and all other inputs at 4.5V.
Note 5: ICC2 is measured with the outputs open and all inputs at 4.5V.
3
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DM74LS251
Absolute Maximum Ratings(Note 1)
DM74LS251
Switching Characteristics
at VCC = 5V and TA = 25°C
RL = 667Ω
From (Input)
Symbol
Parameter
to (Output)
CL = 45 pF
Min
tPLH
Propagation Delay Time
LOW-to-HIGH Level Output
tPHL
Propagation Delay Time
HIGH-to-LOW Level Output
tPLH
Propagation Delay Time
LOW-to-HIGH Level Output
tPHL
Propagation Delay Time
HIGH-to-LOW Level Output
tPLH
Propagation Delay Time
LOW-to-HIGH Level Output
tPHL
Propagation Delay Time
HIGH-to-LOW Level Output
tPLH
Propagation Delay Time
LOW-to-HIGH Level Output
tPHL
Propagation Delay Time
HIGH-to-LOW Level Output
tPZH
Output Enable Time to
HIGH Level Output
tPZL
Output Enable Time to
LOW Level Output
tPHZ
Output Disable Time from
HIGH Level Output (Note 6)
tPLZ
Output Disable Time from
LOW Level Output (Note 6)
tPZH
Output Enable Time to
HIGH Level Output
tPZL
Output Enable Time to
LOW Level Output
tPHZ
Output Disable Time from
HIGH Level Output (Note 6)
tPLZ
Output Disable Time from
LOW Level Output (Note 6)
A, B, C
CL = 150 pF
Min
Units
Max
45
53
ns
45
53
ns
33
38
ns
33
42
ns
D to Y
28
35
ns
D to Y
28
38
ns
D to W
15
25
ns
D to W
15
25
ns
Strobe to Y
45
60
ns
Strobe to Y
40
51
ns
Strobe to Y
45
ns
Strobe to Y
25
ns
Strobe to W
27
40
ns
Strobe to W
40
47
ns
Strobe to W
55
ns
Strobe to W
25
ns
(4 Levels) to Y
A, B, C
(4 Levels) to Y
A, B, C
(3 Levels) to W
A, B, C
(3 Levels) to W
Note 6: CL = 5 pF
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Max
4
DM74LS251
Physical Dimensions inches (millimeters) unless otherwise noted
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
Package Number M16A
5
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DM74LS251 3-STATE 1-of-8 Line Data Selector/Multiplexer
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.
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:
2. A critical component in any component of a life support
device or system whose failure to perform can be reasonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
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 reasonably expected to result in a significant injury to the
user.
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6
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