TECHNICAL DATA
IN74LS138
3-to-8-Line Decoder/Demultiplexer
This schottky-clamped TTL MSI circuit is designed to be used in
high-performance memory-decording or data-routing applications
requiring very short propagation delay time. In high-performance
memory systems this decode can be used to minimize the effects of
system decoding. When employed with high-speed memories utilizing
a fast enable circuit the delay times of this decorder and the enable
time of the memory are usually less than the typical access times of the
memory. This means that the effective system delay introduced by the
schottky-clampled system decoder is negligible.
•
Designed Specifically for High Speed Memory Decoders and Data
Transmission Systems
•
Incorporate 3 Enabler Inputs to Simplify Cascading AND/OR Data
Reception
•
Schottky Clamped for High Performance
ORDERING INFORMATION
IN74LS138N Plastic
IN74LS138D SOIC
T
A
= 0° to 70° C
for all packages
PIN ASSIGNMENT
LOGIC DIAGRAM
FUNCTION TABLE
Inputs
CS1 CS2 CS3
X X H
X H X
L X X
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
A2 A1 A0
X X X
X X X
X X X
L
L
L
L
H
H
H
H
L
L
H
H
L
L
H
H
L
H
L
H
L
H
L
H
Outputs
Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7
H H H H H H H H
H H H H H H H H
H H H H H H H H
L
H
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
H
L
PIN 16 =V
CC
PIN 8 = GND
H = high level (steady state)
L = low level (steady state)
X = don’t care
1
IN74LS138
MAXIMUM RATINGS
*
Symbol
V
CC
V
IN
V
OUT
Tstg
*
Parameter
Supply Voltage
Input Voltage
Output Voltage
Storage Temperature Range
Value
7.0
7.0
5.5
-65 to +150
Unit
V
V
V
°C
Maximum Ratings are those values beyond which damage to the device may occur.
Functional operation should be restricted to the Recommended Operating Conditions.
RECOMMENDED OPERATING CONDITIONS
Symbol
V
CC
V
IH
V
IL
I
OH
I
OL
T
A
Supply Voltage
High Level Input Voltage
Low Level Input Voltage
High Level Output Current
Low Level Output Current
Ambient Temperature Range
0
Parameter
Min
4.75
2.0
0.8
-0.4
8.0
+70
Max
5.25
Unit
V
V
V
mA
mA
°C
DC ELECTRICAL CHARACTERISTICS
over full operating conditions
Guaranteed Limit
Symbol
V
IK
V
OH
V
OL
I
IH
I
IL
I
O
I
CC
Parameter
Input Clamp Voltage
High Level Output Voltage
Low Level Output Voltage
High Level Input Current
Low Level Input Current
Output Short Circuit Current
Supply Current
Test Conditions
V
CC
= min, I
IN
= -18 mA
V
CC
= min, I
OH
= -0.4 mA
V
CC
= min, I
OL
= 4 mA
V
CC
= min, I
OL
= 8 mA
V
CC
= max, V
IN
= 2.7 V
V
CC
= max, V
IN
= 7.0 V
V
CC
= max, V
IN
= 0.4 V
V
CC
= max, V
O
= 0 V
(Note 1)
V
CC
= max
Outputs enabled and open
-20
2.7
0.4
0.5
20
0.1
-0.4
-100
10
µA
mA
mA
mA
mA
Min
Max
-1.5
Unit
V
V
V
Note 1: Not more than one output should be shorted at a time, and duration should not exceed one second.
2
IN74LS138
AC ELECTRICAL CHARACTERISTICS
(T
A
=25°C, V
CC
= 5.0 V, C
L
= 15 pF, R
L
= 2 kΩ, t
r
=15
ns, t
f
= 6.0 ns)
Symbol
t
PLH
t
PHL
t
PLH
t
PHL
t
PLH
t
PHL
t
PLH
t
PHL
Parameter
Maximum Propagation Delay, Input A to
Output Y
Maximum Propagation Delay, Input A to
Output Y
Maximum Propagation Delay, Input A to
Output Y
Maximum Propagation Delay, Input A to
Output Y
Maximum Propagation Delay , CS1 to
Output Y
Maximum Propagation Delay , CS1 to
Output Y
Maximum Output Transition Time , CS2 or CS3
to Output Y
Maximum Output Transition Time , CS2 or CS3
to Output Y
2
32
ns
3
38
18
ns
ns
3
39
26
ns
ns
Level
2
41
27
ns
ns
Min
Max
20
Unit
ns
Figure 1. Switching Waveforms
Figure 2. Switching Waveforms
NOTES A. C
L
includes probe and jig capacitance.
B. All diodes are 1N916 or 1N3064.
Figure 3. Switching Waveforms
Figure 4. Test Circuit
3
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