Semiconductor Components Industries, LLC, 1999
December, 1999 Rev. 6
1
Publication Order Number:
SN74LS138/D
SN74LS138
1-of-8 Decoder/
Demultiplexer
The LSTTL / MSI SN74LS138 is a high speed 1-of-8 Decoder /
Demultiplexer. This device is ideally suited for high speed bipolar
memory chip select address decoding. The multiple input enables
allow parallel expansion to a 1-of-24 decoder using just three LS138
devices or to a 1-of-32 decoder using four LS138s and one inverter.
The LS138 is fabricated with the Schottky barrier diode process for
high speed and is completely compatible with all ON Semiconductor
TTL families.
Demultiplexing Capability
Multiple Input Enable for Easy Expansion
Typical Power Dissipation of 32 mW
Active Low Mutually Exclusive Outputs
Input Clamp Diodes Limit High Speed Termination Effects
GUARANTEED OPERATING RANGES
Symbol
Parameter
Min
Typ
Max
Unit
V
CC
Supply Voltage
4.75
5.0
5.25
V
T
A
Operating Ambient
Temperature Range
0
25
70
C
I
OH
Output Current High
0.4
mA
I
OL
Output Current Low
8.0
mA
LOW
POWER
SCHOTTKY
Device
Package
Shipping
ORDERING INFORMATION
SN74LS138N
16 Pin DIP
2000 Units/Box
SN74LS138D
16 Pin
SOIC
D SUFFIX
CASE 751B
http://onsemi.com
2500/Tape & Reel
PLASTIC
N SUFFIX
CASE 648
16
1
16
1
SN74LS138
http://onsemi.com
2
CONNECTION DIAGRAM DIP (TOP VIEW)
Address Inputs
Enable (Active LOW) Inputs
Enable (Active HIGH) Input
Active LOW Outputs
A
0
A
2
E
1
, E
2
E
3
O
0
O
7
0.5 U.L.
0.5 U.L.
0.5 U.L.
10 U.L.
0.25 U.L.
0.25 U.L.
0.25 U.L.
5 U.L.
NOTES:
a) 1 TTL Unit Load (U.L.) = 40
mA HIGH/1.6 mA LOW.
HIGH
LOW
(Note a)
LOADING
PIN NAMES
NOTE:
The Flatpak version has the same
pinouts (Connection Diagram) as
the Dual In-Line Package.
14
13
12
11
10
9
1
2
3
4
5
6
7
16
15
8
V
CC
O
0
GND
O
1
O
2
O
3
O
4
O
5
O
6
A
0
E
1
E
2
E
3
O
7
A
1
A
2
LOGIC SYMBOL
V
CC
= PIN 16
GND = PIN 8
15 14 13 12 11 10 9
1 2 3
4 5 6
1 2 3
A
0
A
1
A
2
E
O
0
O
1
O
2
O
3
O
4
O
5
O
6
O
7
7
SN74LS138
http://onsemi.com
3
LOGIC DIAGRAM
A
2
A
1
A
0
E
1
E
2
E
3
O
7
O
6
O
5
O
4
O
3
O
2
O
1
O
0
V
CC
= PIN 16
GND = PIN 8
= Pin Numbers
3
2
1
4
5
6
7
9
15
14
13
12
11
10
SN74LS138
http://onsemi.com
4
FUNCTIONAL DESCRIPTION
The LS138 is a high speed 1-of-8 Decoder/Demultiplexer
fabricated with the low power Schottky barrier diode
process. The decoder accepts three binary weighted inputs
(A
0
, A
1
, A
2
) and when enabled provides eight mutually
exclusive active LOW Outputs (O
0
O
7
). The LS138
features three Enable inputs, two active LOW (E
1
, E
2
) and
one active HIGH (E
3
). All outputs will be HIGH unless E
1
and E
2
are LOW and E
3
is HIGH. This multiple enable
function allows easy parallel expansion of the device to a
1-of-32 (5 lines to 32 lines) decoder with just four LS138s
and one inverter. (See Figure a.)
The LS138 can be used as an 8-output demultiplexer by
using one of the active LOW Enable inputs as the data input
and the other Enable inputs as strobes. The Enable inputs
which are not used must be permanently tied to their
appropriate active HIGH or active LOW state.
TRUTH TABLE
INPUTS
OUTPUTS
E
1
E
2
E
3
A
0
A
1
A
2
O
0
O
1
O
2
O
3
O
4
O
5
O
6
O
7
H
X
X
X
X
X
H
H
H
H
H
H
H
H
X
H
X
X
X
X
H
H
H
H
H
H
H
H
X
X
L
X
X
X
H
H
H
H
H
H
H
H
L
L
H
L
L
L
L
H
H
H
H
H
H
H
L
L
H
H
L
L
H
L
H
H
H
H
H
H
L
L
H
L
H
L
H
H
L
H
H
H
H
H
L
L
H
H
H
L
H
H
H
L
H
H
H
H
L
L
H
L
L
H
H
H
H
H
L
H
H
H
L
L
H
H
L
H
H
H
H
H
H
L
H
H
L
L
H
L
H
H
H
H
H
H
H
H
L
H
L
L
H
H
H
H
H
H
H
H
H
H
H
L
H = HIGH Voltage Level
L = LOW Voltage Level
X = Don't Care
O
0
O
31
A
0
A
1
A
2
A
3
A
4
H
LS04
A
0
A
1
A
2
E
LS138
O
0
O
1
O
2
O
3
O
4
O
5
O
6
O
7
LS138
1 2 3
1 2 3
1 2 3
1 2 3
Figure a
LS138
LS138
A
0
A
1
A
2
E
O
0
O
1
O
2
O
3
O
4
O
5
O
6
O
7
A
0
A
1
A
2
E
O
0
O
1
O
2
O
3
O
4
O
5
O
6
O
7
A
0
A
1
A
2
E
O
0
O
1
O
2
O
3
O
4
O
5
O
6
O
7
SN74LS138
http://onsemi.com
5
DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified)
Limits
Symbol
Parameter
Min
Typ
Max
Unit
Test Conditions
V
IH
Input HIGH Voltage
2.0
V
Guaranteed Input HIGH Voltage for
All Inputs
V
IL
Input LOW Voltage
0.8
V
Guaranteed Input LOW Voltage for
All Inputs
V
IK
Input Clamp Diode Voltage
0.65
1.5
V
V
CC
= MIN, I
IN
= 18 mA
V
OH
Output HIGH Voltage
2.7
3.5
V
V
CC
= MIN, I
OH
= MAX, V
IN
= V
IH
or V
IL
per Truth Table
V
O
Output LOW Voltage
0.25
0.4
V
I
OL
= 4.0 mA
V
CC
= V
CC
MIN,
V
IN
= V
IL
or V
IH
V
OL
Output LOW Voltage
0.35
0.5
V
I
OL
= 8.0 mA
V
IN
= V
IL
or V
IH
per Truth Table
I
Input HIGH Current
20
A
V
CC
= MAX, V
IN
= 2.7 V
I
IH
Input HIGH Current
0.1
mA
V
CC
= MAX, V
IN
= 7.0 V
I
IL
Input LOW Current
0.4
mA
V
CC
= MAX, V
IN
= 0.4 V
I
OS
Short Circuit Current (Note 1)
20
100
mA
V
CC
= MAX
I
CC
Power Supply Current
10
mA
V
CC
= MAX
Note 1: Not more than one output should be shorted at a time, nor for more than 1 second.
AC CHARACTERISTICS
(T
A
= 25
C)
Levels of
Limits
Symbol
Parameter
Levels of
Delay
Min
Typ
Max
Unit
Test Conditions
t
PLH
t
PHL
Propagation Delay
Address to Output
2
2
13
27
20
41
ns
t
PLH
t
PHL
Propagation Delay
Address to Output
3
3
18
26
27
39
ns
V
CC
= 5.0 V
t
PLH
t
PHL
Propagation Delay E
1
or E
2
Enable to Output
2
2
12
21
18
32
ns
CC
C
L
= 15 pF
t
PLH
t
PHL
Propagation Delay E
3
Enable to Output
3
3
17
25
26
38
ns
AC WAVEFORMS
Figure 1.
Figure 2.
V
IN
V
OUT
1.3 V
t
PHL
1.3 V
1.3 V
1.3 V
t
PLH
V
IN
V
OUT
1.3 V
t
PHL
1.3 V
t
PLH
1.3 V
1.3 V
SN74LS138
http://onsemi.com
6
PACKAGE DIMENSIONS
N SUFFIX
PLASTIC PACKAGE
CASE 64808
ISSUE R
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
3. DIMENSION L TO CENTER OF LEADS WHEN
FORMED PARALLEL.
4. DIMENSION B DOES NOT INCLUDE MOLD FLASH.
5. ROUNDED CORNERS OPTIONAL.
A
B
F
C
S
H
G
D
J
L
M
16 PL
SEATING
1
8
9
16
K
PLANE
T
M
A
M
0.25 (0.010)
T
DIM
MIN
MAX
MIN
MAX
MILLIMETERS
INCHES
A
0.740
0.770
18.80
19.55
B
0.250
0.270
6.35
6.85
C
0.145
0.175
3.69
4.44
D
0.015
0.021
0.39
0.53
F
0.040
0.70
1.02
1.77
G
0.100 BSC
2.54 BSC
H
0.050 BSC
1.27 BSC
J
0.008
0.015
0.21
0.38
K
0.110
0.130
2.80
3.30
L
0.295
0.305
7.50
7.74
M
0
10
0
10
S
0.020
0.040
0.51
1.01
_
_
_
_
SN74LS138
http://onsemi.com
7
PACKAGE DIMENSIONS
D SUFFIX
PLASTIC SOIC PACKAGE
CASE 751B05
ISSUE J
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSIONS A AND B DO NOT INCLUDE
MOLD PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15 (0.006)
PER SIDE.
5. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.127 (0.005) TOTAL
IN EXCESS OF THE D DIMENSION AT
MAXIMUM MATERIAL CONDITION.
1
8
16
9
SEATING
PLANE
F
J
M
R
X 45
_
G
8 PL
P
B
A
M
0.25 (0.010)
B
S
T
D
K
C
16 PL
S
B
M
0.25 (0.010)
A
S
T
DIM
MIN
MAX
MIN
MAX
INCHES
MILLIMETERS
A
9.80
10.00
0.386
0.393
B
3.80
4.00
0.150
0.157
C
1.35
1.75
0.054
0.068
D
0.35
0.49
0.014
0.019
F
0.40
1.25
0.016
0.049
G
1.27 BSC
0.050 BSC
J
0.19
0.25
0.008
0.009
K
0.10
0.25
0.004
0.009
M
0
7
0
7
P
5.80
6.20
0.229
0.244
R
0.25
0.50
0.010
0.019
_
_
_
_
SN74LS138
http://onsemi.com
8
ON Semiconductor and are trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes
without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular
purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability,
including without limitation special, consequential or incidental damages. "Typical" parameters which may be provided in SCILLC data sheets and/or
specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals" must be
validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights nor the rights of others.
SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications
intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or
death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold
SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable
attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim
alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer.
PUBLICATION ORDERING INFORMATION
ASIA/PACIFIC: LDC for ON Semiconductor Asia Support
Phone:
3036752121 (TueFri 9:00am to 1:00pm, Hong Kong Time)
Toll Free from Hong Kong 80044223781
Email: ONlitasia@hibbertco.com
JAPAN: ON Semiconductor, Japan Customer Focus Center
4321 NishiGotanda, Shinagawaku, Tokyo, Japan 1418549
Phone: 81354878345
Email: r14153@onsemi.com
Fax Response Line:
3036752167
8003443810 Toll Free USA/Canada
ON Semiconductor Website: http://onsemi.com
For additional information, please contact your local
Sales Representative.
SN74LS138/D
North America Literature Fulfillment:
Literature Distribution Center for ON Semiconductor
P.O. Box 5163, Denver, Colorado 80217 USA
Phone: 3036752175 or 8003443860 Toll Free USA/Canada
Fax: 3036752176 or 8003443867 Toll Free USA/Canada
Email: ONlit@hibbertco.com
N. American Technical Support: 8002829855 Toll Free USA/Canada
EUROPE: LDC for ON Semiconductor European Support
German Phone: (+1) 3033087140 (MF 2:30pm to 5:00pm Munich Time)
Email: ONlitgerman@hibbertco.com
French Phone: (+1) 3033087141 (MF 2:30pm to 5:00pm Toulouse Time)
Email: ONlitfrench@hibbertco.com
English Phone: (+1) 3033087142 (MF 1:30pm to 5:00pm UK Time)
Email: ONlit@hibbertco.com
PDF 
ZIP