DM74LS257 [FAIRCHILD]
3-STATE Quad 2-Data Selectors/Multiplexers; 三态四路2数据选择器/多路复用器
| 型号： | DM74LS257 |
| 厂家： | 
FAIRCHILD SEMICONDUCTOR |
| 描述： | 3-STATE Quad 2-Data Selectors/Multiplexers |
| 文件： | 总5页 (文件大小：59K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
June 1989
Revised November 1999
DM74LS257B
3-STATE Quad 2-Data Selectors/Multiplexers
for data buses. It also permits the use of standard TTL reg-
isters for data retention throughout the system.
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.
Features
■ 3-STATE versions LS157 and LS158 with same pinouts
■ Schottky-clamped for significant improvement in A-C
performance
■ Provides bus interface from multiple sources in
high-performance systems
■ Average propagation delay from data input 12 ns
■ Typical power dissipation: 50 mW
This 3-STATE output feature means that n-bit (paralleled)
data selectors with up to 258 sources can be implemented
Ordering Code:
Order Number Package Number
Package Description
DM74LS257BM
DM74LS257BN
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
Logic Diagram
Function Table
Inputs
Output
Output Y
LS257
Select
A
B
Control
H
L
L
L
L
X
L
X
L
X
X
X
L
Z
L
L
H
X
X
H
L
H
H
H
H
H = HIGH Level
L = LOW Level
X = Don’t Care
Z = High Impedance (off)
© 1999 Fairchild Semiconductor Corporation
DS006417
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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.
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
VCC
VIH
Parameter
Min
4.75
2
Nom
Max
Units
V
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
VIL
0.8
−2.6
24
V
IOH
mA
mA
°C
IOL
TA
0
70
DC Electrical Characteristics
Typ
Symbol
Parameter
Conditions
CC = Min, II = −18 mA
Min
Max
Units
(Note 2)
VI
Input Clamp Voltage
V
V
V
−1.5
V
V
VOH
VOL
HIGH Level Output Voltage
LOW Level Output
IL = Max, VIH = Min
IL = Max, VIH = Min
2.4
3.1
0.35
0.25
0.5
0.4
0.2
0.1
40
V
Voltage
I
OL = 12 mA, VCC = Min
CC = Max,
VI = 7V
CC = Max,
VI = 2.7V
CC = Max,
VI = 0.4V
II
Input Current @ Max
V
Select
mA
µA
mA
µA
µA
Input Voltage
Other
Select
Other
Select
Other
IIH
HIGH Level Input
V
Current
20
IIL
LOW Level Input
V
−0.8
−0.4
Current
IOZH
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
Supply Current with Outputs Disabled
VCC = Max, VO = 2.7V
VIH = Min, VIL = Max
VCC = Max, VO = 0.4V
VIH = Min, VIL = Max
VCC = Max (Note 3)
VCC = Max (Note 4)
VCC = Max (Note 4)
VCC = Max (Note 4)
20
IOZL
−20
IOS
−20
−100
10
mA
mA
mA
mA
ICCH
ICCL
ICCZ
5.9
9.2
12
16
19
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: ICC is measured with all outputs open and all possible inputs grounded, while achieving the stated output conditions.
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2
Switching Characteristics
V
CC = 5V and T = 25°C
A
RL = 667Ω
C
L = 45 pF
C
L = 150 pF
Symbol
Parameter
From (Input)
To (Output)
Units
Min
Max
Min Max
tPLH
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
Data to Output
18
18
28
35
15
28
28
25
27
27
35
42
27
38
ns
ns
ns
ns
ns
ns
ns
ns
tPHL
tPLH
tPHL
tPZH
tPZL
tPHZ
tPLZ
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
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: CL = 5 pF
3
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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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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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