SN54ALS138A, SN54AS138, SN74ALS138A, SN74AS138
3-LINE TO 8-LINE DECODERS/DEMULTIPLEXERS
SDAS055E – APRIL 1982 – REVISED JULY 1996
D
D
D
Designed Specifically for High-Speed
Memory Decoders and Data Transmission
Systems
Incorporate Three Enable Inputs to Simplify
Cascading and /or Data Reception
Package Options Include Plastic
Small-Outline (D) Packages, Ceramic Chip
Carriers (FK), and Standard Plastic (N) and
Ceramic (J) 300-mil DIPs
SN54ALS138A, SN54AS138 . . . J PACKAGE
SN74ALS138A, SN74AS138 . . . D OR N PACKAGE
(TOP VIEW)
description
The
′ALS138A
and
′AS138
are 3-line to 8-line
decoders/demultiplexers designed for high-
performance memory-decoding or data-routing
applications requiring very short propagation
delay times. In high-performance systems, these
devices can be used to minimize the effects of
system decoding. When employed with
high-speed memories with a fast enable circuit,
the delay times of the decoder and the enable time
of the memory are usually less than the typical
access time of the memory. The effective system
delay introduced by the Schottky-clamped system
decoder is negligible.
A
B
C
G2A
G2B
G1
Y7
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
CC
Y0
Y1
Y2
Y3
Y4
Y5
Y6
SN54ALS138A, SN54AS138 . . . FK PACKAGE
(TOP VIEW)
C
G2A
NC
G2B
G1
4
5
6
7
8
3 2 1 20 19
18
17
16
15
14
9 10 11 12 13
B
A
NC
V
CC
Y0
Y1
Y2
NC
Y3
Y4
Copyright
©
1996, Texas Instruments Incorporated
The conditions at the binary-select (A, B, and C)
inputs and the three enable (G1, G2A, and G2B)
NC – No internal connection
inputs select one of eight output lines. Two
active-low and one active-high enable inputs
reduce the need for external gates or inverters when expanding. A 24-line decoder can be implemented without
external inverters and a 32-line decoder requires only one inverter. An enable input can be used as a data input
for demultiplexing applications.
The SN54ALS138A and SN54AS138 are characterized for operation over the full military temperature range
of – 55°C to 125°C. The SN74ALS138A and SN74AS138 are characterized for operation from 0°C to 70°C.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
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.
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
Y7
GND
NC
Y6
Y5
1
SN54ALS138A, SN54AS138, SN74ALS138A, SN74AS138
3-LINE TO 8-LINE DECODERS/DEMULTIPLEXERS
SDAS055E – APRIL 1982 – REVISED JULY 1996
FUNCTION TABLE
INPUTS
ENABLE
G1
X
X
L
H
H
H
H
H
H
H
H
G2A
H
X
X
L
L
L
L
L
L
L
L
G2B
X
H
X
L
L
L
L
L
L
L
L
C
X
X
X
L
L
L
L
H
H
H
H
SELECT
B
X
X
X
L
L
H
H
L
L
H
H
A
X
X
X
L
H
L
H
L
H
L
H
Y0
H
H
H
L
H
H
H
H
H
H
H
Y1
H
H
H
H
L
H
H
H
H
H
H
Y2
H
H
H
H
H
L
H
H
H
H
H
OUTPUTS
Y3
H
H
H
H
H
H
L
H
H
H
H
Y4
H
H
H
H
H
H
H
L
H
H
H
Y5
H
H
H
H
H
H
H
H
L
H
H
Y6
H
H
H
H
H
H
H
H
H
L
H
Y7
H
H
H
H
H
H
H
H
H
H
L
logic symbols (alternatives)
†
A
B
C
1
2
3
BIN/OCT
1
2
4
&
EN
0
1
2
3
4
5
6
7
15
14
13
12
11
10
9
7
Y0
Y1
Y2
Y3
Y4
Y5
Y6
Y7
G1
G2A
G2B
5
6
4
A
B
C
1
2
3
2
&
DMUX
0
G
0
7
0
1
2
3
4
5
6
7
15
14
13
12
11
10
9
7
Y0
Y1
Y2
Y3
Y4
Y5
Y6
Y7
G1
G2A
G2B
6
4
5
† These symbols are in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
Pin numbers shown are for the D, J, and N packages.
2
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
SN54ALS138A, SN54AS138, SN74ALS138A, SN74AS138
3-LINE TO 8-LINE DECODERS/DEMULTIPLEXERS
SDAS055E – APRIL 1982 – REVISED JULY 1996
logic diagram (positive logic)
15
A
1
14
Y1
Y0
13
Select
Inputs
B
2
12
Y2
Y3
Data
Outputs
Y4
C
3
11
10
Y5
9
G2A
Enable
Inputs
G2B
G1
4
7
5
6
Y6
Y7
Pin numbers shown are for the D, J, and N packages.
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
3
SN54ALS138A, SN54AS138, SN74ALS138A, SN74AS138
3-LINE TO 8-LINE DECODERS/DEMULTIPLEXERS
SDAS055E – APRIL 1982 – REVISED JULY 1996
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
†
Supply voltage, V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
Input voltage, V
I
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
Operating free-air temperature range, T
A
: SN54ALS138A . . . . . . . . . . . . . . . . . . . . . . . . . . . – 55°C to 125°C
SN74ALS138A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 70°C
Storage temperature range, T
stg
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 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
SN54ALS138A
MIN
VCC
VIH
VIL
IOH
IOL
TA
Supply voltage
High-level input voltage
Low-level input voltage
High-level output current
Low-level output current
Operating free-air temperature
– 55
4.5
2
0.7
– 0.4
4
125
0
NOM
5
MAX
5.5
SN74ALS138A
MIN
4.5
2
0.8
– 0.4
8
70
NOM
5
MAX
5.5
UNIT
V
V
V
mA
mA
°C
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
PARAMETER
VIK
VOH
VOL
II
IIH
IIL
IO§
VCC = 4.5 V,
VCC = 4.5 V,
VCC = 4 5 V
4.5
VCC = 5.5 V,
VCC = 5.5 V,
VCC = 5.5 V,
VCC = 5.5 V,
TEST CONDITIONS
II = – 18 mA
IOH = – 0.4 mA
IOL = 4 mA
IOL = 8 mA
VI = 7 V
VI = 2.7 V
VI = 0.4 V
VO = 2.25 V
– 20
SN54ALS138A
MIN TYP‡
MAX
– 1.5
VCC – 2
0.25
0.4
0.1
20
– 0.1
– 112
– 30
VCC – 2
0.25
0.35
0.4
0.5
0.1
20
– 0.1
– 112
SN74ALS138A
MIN TYP‡
MAX
– 1.5
UNIT
V
V
V
mA
µA
mA
mA
ICC
VCC = 5.5 V
5
10
5
10
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.
switching characteristics (see Figure 1)
VCC = 4.5 V to 5.5 V,
CL = 50 pF,
RL = 500
Ω
,
TA = MIN to MAX¶
SN54ALS138A SN74ALS138A
MIN
tPLH
tPHL
tPLH
tPHL
A, B,
A B C
G or G
Any Y
Any Y
2
6
2
4
MAX
28
22
22
21
MIN
5
6
3
4
MAX
22
18
17
17
ns
ns
PARAMETER
FROM
(INPUT)
TO
(OUTPUT)
UNIT
¶ For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions.
4
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
SN54ALS138A, SN54AS138, SN74ALS138A, SN74AS138
3-LINE TO 8-LINE DECODERS/DEMULTIPLEXERS
SDAS055E – APRIL 1982 – REVISED JULY 1996
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
†
Supply voltage, V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
Input voltage, V
I
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
Operating free-air temperature range, T
A
: SN54AS138 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 55°C to 125°C
SN74AS138 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 70°C
Storage temperature range, T
stg
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 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
SN54AS138
MIN
VCC
VIH
VIL
IOH
IOL
TA
Supply voltage
High-level input voltage
Low-level input voltage
High-level output current
Low-level output current
Operating free-air temperature
– 55
4.5
2
0.8
–2
20
125
0
NOM
5
MAX
5.5
SN74AS138
MIN
4.5
2
0.8
–2
20
70
NOM
5
MAX
5.5
UNIT
V
V
V
mA
mA
°C
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
PARAMETER
VIK
VOH
VOL
II
IIH
IIL
IO§
ICCH
ICCL
TEST CONDITIONS
VCC = 4.5 V,
VCC = 4.5 V to 5.5 V,
VCC = 4.5 V,
VCC = 5.5 V,
VCC = 5.5 V,
VCC = 5.5 V,
VCC = 5.5 V,
VCC = 5.5 V
II = – 18 mA
IOH = – 2 mA
IOL = 20 mA
VI = 7 V
VI = 2.7 V
VI = 0.4 V
VO = 2.25 V
– 30
12
SN54AS138
MIN TYP‡
MAX
– 1.2
VCC – 2
0.35
0.5
0.1
20
– 0.5
– 112
17.5
– 30
12
VCC – 2
0.35
0.5
0.1
20
– 0.5
– 112
17.5
SN74AS138
MIN TYP‡
MAX
– 1.2
UNIT
V
V
V
mA
µA
mA
mA
mA
VCC = 5.5 V
14
20
14
20
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.
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
5
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