SN54ALS251, SN74ALS251
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDAS215A APRIL 1982 REVISED DECEMBER 1994
Copyright
1994, Texas Instruments Incorporated
1
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
3-State Version of the
ALS151
3-State Outputs Interface Directly With
System Bus
Perform Parallel-to-Serial Conversion
Complementary Outputs Provide True and
Inverted Data
Package Options Include Plastic
Small-Outline (D) Packages, Ceramic Chip
Carriers (FK), and Standard Plastic (N) and
Ceramic (J) 300-mil DIPs
description
These data selectors/multiplexers contain full
binary decoding to select one-of-eight data
sources and feature controlled complementary
3-state outputs.
The 3-state outputs can interface with and drive
data lines of bus-organized systems. With all but
one of the common outputs disabled (at the
high-impedance state), the low impedance of the
signal-enabled output drives the bus line to a high
or low logic level. Both outputs are controlled by
the output-enable (OE) input. The outputs are
disabled when OE is high.
The SN54ALS251 is characterized for operation
over the full military temperature range of 55
C
to 125
C. The SN74ALS251 is characterized for
operation from 0
C to 70
C.
FUNCTION TABLE
INPUTS
OUTPUTS
SELECT
OE
OUTPUTS
C
B
A
OE
Y
W
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
D0, D1, . . . D7 = the level of the respective D input
SN54ALS251 . . . J PACKAGE
SN74ALS251 . . . D OR N PACKAGE
(TOP VIEW)
3
2
1 20 19
9 10 11 12 13
4
5
6
7
8
18
17
16
15
14
D5
D6
NC
D7
A
D1
D0
NC
Y
W
SN54ALS251 . . . FK PACKAGE
(TOP VIEW)
D2
D3
NC
C
B
D4
OE
GND
NC
NC No internal connection
V
CC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
D3
D2
D1
D0
Y
W
OE
GND
V
CC
D4
D5
D6
D7
A
B
C
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
SN54ALS251, SN74ALS251
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDAS215A APRIL 1982 REVISED DECEMBER 1994
2
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
logic symbol
MUX
EN
7
0
11
A
10
B
2
9
C
0
4
D0
1
3
D1
2
2
D2
3
1
D3
4
15
D4
5
14
D5
6
13
D6
7
12
D7
0
7
G
W
6
Y
5
OE
This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
Pin numbers shown are for the D, J, and N packages.
logic diagram (positive logic)
7
4
3
2
1
15
14
13
12
11
10
9
5
6
OE
D0
D1
D2
D3
D4
D5
D6
D7
A
B
C
Y
W
Data
Inputs
Data
Select
(binary)
Pin numbers shown are for the D, J, and N packages.
SN54ALS251, SN74ALS251
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDAS215A APRIL 1982 REVISED DECEMBER 1994
3
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Supply voltage, V
CC
7 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input voltage, V
I
7 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Voltage applied to a disabled 3-state output
5.5 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating free-air temperature range, T
A
: SN54ALS251
55
C to 125
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SN74ALS251
0
C to 70
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range
65
C to 150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
recommended operating conditions
SN54ALS251
SN74ALS251
UNIT
MIN
NOM
MAX
MIN
NOM
MAX
UNIT
VCC
Supply voltage
4.5
5
5.5
4.5
5
5.5
V
VIH
High-level input voltage
2
2
V
VIL
Low-level input voltage
0.7
0.8
V
IOH
High-level output current
1
2.6
mA
IOL
Low-level output current
12
24
mA
TA
Operating free-air temperature
55
125
0
70
C
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
PARAMETER
TEST CONDITIONS
SN54ALS251
SN74ALS251
UNIT
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
UNIT
VIK
VCC = 4.5 V,
II = 18 mA
1.5
1.5
V
VCC = 4.5 V to 5.5 V,
IOH = 0.4 mA
VCC 2
VCC 2
VOH
VCC = 4 5 V
IOH = 1 mA
2.4
3.3
V
VCC = 4.5 V
IOH = 2.6 mA
2.4
3.2
VOL
VCC = 4 5 V
IOL = 12 mA
0.25
0.4
0.25
0.4
V
VOL
VCC = 4.5 V
IOL = 24 mA
0.35
0.5
V
IOZH
VCC = 5.5 V,
VO = 2.7 V
20
20
A
IOZL
VCC = 5.5 V,
VO = 0.4 V
20
20
A
II
VCC = 5.5 V,
VI = 7 V
0.1
0.1
mA
IIH
VCC = 5.5 V,
VI = 2.7 V
20
20
A
IIL
VCC = 5.5 V,
VI = 0.4 V
0.1
0.1
mA
IO
VCC = 5.5 V,
VO = 4.5 V
20
112
30
112
mA
ICC
Enabled
VCC = 5 5 V
Inputs at GND
7
10
7
10
mA
ICC
Disabled
VCC = 5.5 V
Inputs at 4.5 V
9.4
14
9.4
14
mA
All typical values are at VCC = 5 V, TA = 25
C.
The output conditions have been chosen to produce a current that closely approximates one half of the true short-circuit output current, IOS.
SN54ALS251, SN74ALS251
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDAS215A APRIL 1982 REVISED DECEMBER 1994
4
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
switching characteristics (see Figure 1)
PARAMETER
FROM
(INPUT)
TO
(OUTPUT)
VCC = 4.5 V to 5.5 V,
CL = 50 pF,
R1 = 500
,
R2 = 500
,
TA = MIN to MAX
UNIT
SN54ALS251
SN74ALS251
MIN
MAX
MIN
MAX
tPLH
A B or C
Y
1
21
5
18
ns
tPHL
A, B, or C
Y
7
34
8
24
ns
tPLH
A B or C
W
5
38
8
24
ns
tPHL
A, B, or C
W
7
26
7
23
ns
tPLH
An D
Y
2
15
2
10
ns
tPHL
Any D
Y
3
23
3
15
ns
tPLH
An D
W
3
25
3
15
ns
tPHL
Any D
W
3
20
3
15
ns
tPZH
OE
Y
3
21
3
15
ns
tPZL
OE
Y
3
19
3
15
ns
tPZH
OE
W
3
21
3
15
ns
tPZL
OE
W
3
19
3
15
ns
tPZH
OE
Y
2
12
2
10
ns
tPZL
OE
Y
1
18
1
10
ns
tPZH
OE
W
2
12
2
10
ns
tPZL
OE
W
1
18
1
10
ns
For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions.
SN54ALS251, SN74ALS251
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDAS215A APRIL 1982 REVISED DECEMBER 1994
5
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
PARAMETER MEASUREMENT INFORMATION
SERIES 54ALS/ 74ALS AND 54AS/ 74AS DEVICES
tPHZ
tPLZ
tPHL
tPLH
0.3 V
tPZL
tPZH
tPLH
tPHL
LOAD CIRCUIT
FOR 3-STATE OUTPUTS
From Output
Under Test
Test
Point
R1
S1
CL
(see Note A)
7 V
1.3 V
1.3 V
1.3 V
3.5 V
3.5 V
0.3 V
0.3 V
th
tsu
VOLTAGE WAVEFORMS
SETUP AND HOLD TIMES
Timing
Input
Data
Input
1.3 V
1.3 V
3.5 V
3.5 V
0.3 V
0.3 V
High-Level
Pulse
Low-Level
Pulse
tw
VOLTAGE WAVEFORMS
PULSE DURATIONS
Input
Out-of-Phase
Output
(see Note C)
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
3.5 V
3.5 V
0.3 V
0.3 V
VOL
VOH
VOH
VOL
Output
Control
(low-level
enabling)
Waveform 1
S1 Closed
(see Note B)
Waveform 2
S1 Open
(see Note B)
[
0 V
VOH
VOL
[
3.5 V
In-Phase
Output
0.3 V
1.3 V
1.3 V
VOLTAGE WAVEFORMS
PROPAGATION DELAY TIMES
VOLTAGE WAVEFORMS
ENABLE AND DISABLE TIMES, 3-STATE OUTPUTS
R2
VCC
RL
Test
Point
From Output
Under Test
CL
(see Note A)
LOAD CIRCUIT
FOR OPEN-COLLECTOR OUTPUTS
LOAD CIRCUIT FOR
BI-STATE
TOTEM-POLE OUTPUTS
From Output
Under Test
Test
Point
CL
(see Note A)
RL
RL = R1 = R2
NOTES: A. CL includes probe and jig capacitance.
B. Waveform 1 is for an output with internal conditions such that the output is low except when disabled by the output control.
Waveform 2 is for an output with internal conditions such that the output is high except when disabled by the output control.
C. When measuring propagation delay items of 3-state outputs, switch S1 is open.
D. All input pulses have the following characteristics: PRR
1 MHz, tr = tf = 2 ns, duty cycle = 50%.
E. The outputs are measured one at a time with one transition per measurement.
Figure 1. Load Circuits and Voltage Waveforms
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Copyright
1998, Texas Instruments Incorporated
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