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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 http://onsemi.com
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 LOW
high speed and is completely compatible with all ON Semiconductor POWER
TTL families.
• Demultiplexing Capability SCHOTTKY
• 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 16

Symbol Parameter Min Typ Max Unit 1

VCC Supply Voltage 4.75 5.0 5.25 V PLASTIC

N SUFFIX
TA Operating Ambient 0 25 70 °C
CASE 648
Temperature Range
IOH Output Current – High – 0.4 mA
IOL Output Current – Low 8.0 mA

16
1

SOIC
D SUFFIX
CASE 751B

ORDERING INFORMATION

Device Package Shipping

SN74LS138N 16 Pin DIP 2000 Units/Box

SN74LS138D 16 Pin 2500/Tape & Reel

 Semiconductor Components Industries, LLC, 1999 1 Publication Order Number:

December, 1999 – Rev. 6 SN74LS138/D
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CONNECTION DIAGRAM DIP (TOP VIEW)

VCC O0 O1 O2 O3 O4 O5 O6
16 15 14 13 12 11 10 9

NOTE:
The Flatpak version has the same
pinouts (Connection Diagram) as
the Dual In-Line Package.

1 2 3 4 5 6 7 8
A0 A1 A2 E1 E2 E3 O7 GND

LOADING (Note a)
PIN NAMES HIGH LOW
A0 – A2 Address Inputs 0.5 U.L. 0.25 U.L.
E1, E2 Enable (Active LOW) Inputs 0.5 U.L. 0.25 U.L.
E3 Enable (Active HIGH) Input 0.5 U.L. 0.25 U.L.
O0 – O7 Active LOW Outputs 10 U.L. 5 U.L.

NOTES:
a) 1 TTL Unit Load (U.L.) = 40 m A HIGH/1.6 mA LOW.

LOGIC SYMBOL
1 2 3 456

1 23

A0 A1 A2 E

O0 O1 O2 O3 O4 O5 O6 O7

15 14 13 12 11 10 9 7

VCC = PIN 16
GND = PIN 8

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LOGIC DIAGRAM

A2 A1 A0 E1 E2 E3
3 2 1 4 5 6 VCC = PIN 16
GND = PIN 8
= Pin Numbers

7 9 10 11 12 13 14 15
O7 O6 O5 O4 O3 O2 O1 O0

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FUNCTIONAL DESCRIPTION
The LS138 is a high speed 1-of-8 Decoder/Demultiplexer function allows easy parallel expansion of the device to a
fabricated with the low power Schottky barrier diode 1-of-32 (5 lines to 32 lines) decoder with just four LS138s
process. The decoder accepts three binary weighted inputs and one inverter. (See Figure a.)
(A0, A1, A2) and when enabled provides eight mutually The LS138 can be used as an 8-output demultiplexer by
exclusive active LOW Outputs (O0 – O7). The LS138 using one of the active LOW Enable inputs as the data input
features three Enable inputs, two active LOW (E1, E2) and and the other Enable inputs as strobes. The Enable inputs
one active HIGH (E3). All outputs will be HIGH unless E1 which are not used must be permanently tied to their
and E2 are LOW and E3 is HIGH. This multiple enable appropriate active HIGH or active LOW state.

TRUTH TABLE
INPUTS OUTPUTS
E1 E2 E3 A0 A1 A2 O0 O1 O2 O3 O4 O5 O6 O7
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

A0
A1
A2
LS04
A3

A4
H

123 123 123 123

A0 A1 A2 E A0 A1 A2 E A0 A1 A2 E A0 A1 A2 E

LS138 LS138 LS138 LS138

O0 O1 O2 O3 O4 O5 O6 O7 O0 O1 O2 O3 O4 O5 O6 O7 O0 O1 O2 O3 O4 O5 O6 O7 O0 O1 O2 O3 O4 O5 O6 O7

O0 O31

Figure a

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DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified)

Limits
Symbol Parameter Min Typ Max Unit Test Conditions
Guaranteed Input HIGH Voltage for
VIH Input HIGH Voltage 2.0 V
All Inputs
0.8 Guaranteed Input LOW Voltage for
VIL Input LOW Voltage V
All Inputs
VIK Input Clamp Diode Voltage – 0.65 – 1.5 V VCC = MIN, IIN = – 18 mA
2.7 3.5 V VCC = MIN, IOH = MAX, VIN = VIH
VOH Output HIGH Voltage
or VIL per Truth Table

0.25 0.4 V IOL = 4.0 mA VCC = VCC MIN,

VOL
O Output LOW Voltage VIN = VIL or VIH
0.35 0.5 V IOL = 8.0 mA per Truth Table

20 µA VCC = MAX, VIN = 2.7 V

IIH Input HIGH Current
0.1 mA VCC = MAX, VIN = 7.0 V
IIL Input LOW Current – 0.4 mA VCC = MAX, VIN = 0.4 V
IOS Short Circuit Current (Note 1) – 20 –100 mA VCC = MAX
ICC Power Supply Current 10 mA VCC = MAX
Note 1: Not more than one output should be shorted at a time, nor for more than 1 second.

AC CHARACTERISTICS (TA = 25°C)

Levels of Limits
Symbol Parameter Delay Min Typ Max Unit Test Conditions
tPLH Propagation Delay 2 13 20
ns
tPHL Address to Output 2 27 41
tPLH Propagation Delay 3 18 27
ns
tPHL Address to Output 3 26 39 VCC = 5.0 V
tPLH Propagation Delay E1 or E2 2 12 18 CL = 15 pF
ns
tPHL Enable to Output 2 21 32
tPLH Propagation Delay E3 3 17 26
ns
tPHL Enable to Output 3 25 38

AC WAVEFORMS

1.3 V 1.3 V VIN

VIN 1.3 V 1.3 V

tPHL tPLH tPHL tPLH

VOUT
1.3 V 1.3 V VOUT 1.3 V 1.3 V

Figure 1. Figure 2.

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PACKAGE DIMENSIONS

N SUFFIX
PLASTIC PACKAGE
CASE 648–08
ISSUE R
NOTES:
–A– 1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
16 9 3. DIMENSION L TO CENTER OF LEADS WHEN
FORMED PARALLEL.
B 4. DIMENSION B DOES NOT INCLUDE MOLD FLASH.
1 8 5. ROUNDED CORNERS OPTIONAL.
INCHES MILLIMETERS
DIM MIN MAX MIN MAX
F C L A 0.740 0.770 18.80 19.55
B 0.250 0.270 6.35 6.85
S C 0.145 0.175 3.69 4.44
D 0.015 0.021 0.39 0.53
SEATING F 0.040 0.70 1.02 1.77
–T– PLANE G 0.100 BSC 2.54 BSC
H 0.050 BSC 1.27 BSC
H K M J 0.008 0.015 0.21 0.38
J K 0.110 0.130 2.80 3.30
G L 0.295 0.305 7.50 7.74
D 16 PL
M 0_ 10 _ 0_ 10 _
0.25 (0.010) M T A M S 0.020 0.040 0.51 1.01

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PACKAGE DIMENSIONS

D SUFFIX
PLASTIC SOIC PACKAGE
CASE 751B–05
ISSUE J

–A–
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
16 9 2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSIONS A AND B DO NOT INCLUDE
–B– MOLD PROTRUSION.
P 8 PL
4. MAXIMUM MOLD PROTRUSION 0.15 (0.006)
1 8
0.25 (0.010) M B S 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.
G
MILLIMETERS INCHES
DIM MIN MAX MIN MAX
F A 9.80 10.00 0.386 0.393
K R X 45 _ 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
C F 0.40 1.25 0.016 0.049
–T– SEATING G 1.27 BSC 0.050 BSC
PLANE
M J J 0.19 0.25 0.008 0.009
K 0.10 0.25 0.004 0.009
D 16 PL M 0_ 7_ 0_ 7_
P 5.80 6.20 0.229 0.244
0.25 (0.010) M T B S A S R 0.25 0.50 0.010 0.019

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