74LS251 [FAIRCHILD]
3-STATE 1-of-8 Line Data Selector/Multiplexer; 3 - STATE 1 - 8线数据选择器/多路复用器
| 型号： | 74LS251 |
| 厂家： | 
FAIRCHILD SEMICONDUCTOR |
| 描述： | 3-STATE 1-of-8 Line Data Selector/Multiplexer |
| 文件： | 总6页 (文件大小：62K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
August 1986
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 3-
STATE outputs permit direct connection to a common bus.
When the strobe input is HIGH, both outputs are in a high-
impedance state in which both the upper and lower transis-
tors of each totem-pole output are OFF, and the output nei-
ther 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 con-
trol 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
DM74LS251N
M16A
N16E
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
Function Table
Inputs
Outputs
Select
Strobe
Y
W
C
X
L
B
X
L
A
X
L
S
H
L
L
L
L
L
L
L
L
Z
Z
D0
D1
D2
D3
D4
D5
D6
D7
D0
D1
D2
D3
D4
D5
D6
D7
L
L
H
L
L
H
H
L
L
H
L
H
H
H
H
L
H
L
H
H
H
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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Logic Diagram
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2
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” table are not guaranteed at the absolute maximum ratings.
The “Recommended Operating Conditions” table will define the conditions
for actual device operation.
Supply Voltage
Input Voltage
7V
7V
Operating Free Air Temperature Range
Storage Temperature Range
0°C to +70°C
−65°C to +150°C
Recommended Operating Conditions
Symbol
Parameter
Min
4.75
2
Nom
Max
Units
V
VCC
VIH
VIL
IOH
IOL
TA
Supply Voltage
5
5.25
HIGH Level Input Voltage
LOW Level Input Voltage
HIGH Level Output Current
LOW Level Output Current
Free Air Operating Temperature
V
0.8
−2.6
24
V
mA
mA
°C
0
70
Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted)
Symbol Parameter Conditions
Input Clamp Voltage = Min, I = −18 mA
Typ
Min
Max
Units
(Note 2)
V
V
V
V
V
V
V
−1.5
V
V
I
CC
CC
I
HIGH Level
= Min, I = Max
OH
OH
2.4
3.1
Output Voltage
LOW Level
= Max, V = Min
IH
IL
V
= Min, I = Max
OL
OL
CC
0.35
0.25
0.5
Output Voltage
= Max, V = Min
V
IL
IH
I
= 12 mA, V = Min
0.4
0.1
20
OL
CC
I
I
I
I
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
V
V
V
V
V
V
V
V
V
V
= Max, V = 7V
mA
µA
I
CC
CC
CC
CC
I
= Max, V = 2.7V
IH
I
= Max, V = 0.4V
−0.4
mA
IL
I
= Max, V = 2.7V
OZH
O
20
µA
µA
= Min, V = Max
IH
IL
I
= Max, V = 0.4V
O
OZL
CC
−20
= Min, V = Max
IH
IL
I
I
I
= Max (Note 3)
= Max (Note 4)
= Max (Note 5)
−20
−100
10
mA
mA
mA
OS
CC
CC
CC
6.1
7.1
CC1
CC2
Supply Current
12
Note 2: All typicals are at V = 5V, T = 25°C.
CC
A
Note 3: Not more than one output should be shorted at a time, and the duration should not exceed one second.
Note 4: I
Note 5: I
is measured with the outputs open, STROBE grounded, and all other inputs at 4.5V.
is measured with the outputs open and all inputs at 4.5V.
CC1
CC2
3
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Switching Characteristics
at VCC = 5V and T = 25°C
A
From (Input)
to (Output)
R = 667Ω
L
Symbol
Parameter
C
= 45 pF
C
= 150 pF
Units
L
L
Min
Max
Min
Max
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
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
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
A, B, C
(4 Levels) to Y
A, B, C
PLH
45
45
33
33
28
28
15
15
45
40
45
25
27
40
55
25
53
53
38
42
35
38
25
25
60
51
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
PHL
PLH
PHL
PLH
PHL
PLH
PHL
PZH
PZL
PHZ
PLZ
PZH
PZL
PHZ
PLZ
(4 Levels) to Y
A, B, C
(3 Levels) to W
A, B, C
(3 Levels) to W
D to Y
D to Y
D to W
D to W
Strobe to Y
Strobe to Y
Strobe to Y
Strobe to Y
Strobe to W
Strobe to W
Strobe to W
Strobe to W
HIGH Level Output
Output Enable Time to
LOW Level Output
Output Disable Time from
HIGH Level Output (Note 6)
Output Disable Time from
LOW Level Output (Note 6)
Output Enable Time to
40
47
HIGH Level Output
Output Enable Time to
LOW Level Output
Output Disable Time from
HIGH Level Output (Note 6)
Output Disable Time from
LOW Level Output (Note 6)
Note 6: C = 5 pF
L
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4
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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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:
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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6
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74LS251B
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