TECHNICAL DATA
1
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
IN74LS138
ORDERING INFORMATION
IN74LS138N Plastic
IN74LS138D SOIC
T
A
= 0
to 70
C
for all packages
PIN ASSIGNMENT
FUNCTION TABLE
Inputs
Outputs
CS1 CS2 CS3
A2 A1 A0
Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7
X X H
X H X
L X X
X X X
X X X
X X X
H 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 L
H L L
H L L
H L L
L L L
L L H
L H L
L 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 L L
H L L
H L L
H L L
H L L
H L H
H H L
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 = high level (steady state)
L = low level (steady state)
X = don't care
LOGIC DIAGRAM
PIN 16 =V
CC
PIN 8 = GND
IN74LS138
2
MAXIMUM RATINGS
*
Symbol
Parameter
Value
Unit
V
CC
Supply Voltage
7.0
V
V
IN
Input Voltage
7.0
V
V
OUT
Output Voltage
5.5
V
Tstg
Storage Temperature Range
-65 to +150
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
Parameter
Min
Max
Unit
V
CC
Supply Voltage
4.75
5.25
V
V
IH
High Level Input Voltage
2.0
V
V
IL
Low Level Input Voltage
0.8
V
I
OH
High Level Output Current
-0.4
mA
I
OL
Low Level Output Current
8.0
mA
T
A
Ambient Temperature Range
0
+70
C
DC ELECTRICAL CHARACTERISTICS over full operating conditions
Guaranteed Limit
Symbol
Parameter
Test Conditions
Min
Max
Unit
V
IK
Input Clamp Voltage
V
CC
= min, I
IN
= -18 mA
-1.5
V
V
OH
High Level Output Voltage
V
CC
= min, I
OH
= -0.4 mA
2.7
V
V
OL
Low Level Output Voltage
V
CC
= min, I
OL
= 4 mA
0.4
V
V
CC
= min, I
OL
= 8 mA
0.5
I
IH
High Level Input Current
V
CC
= max, V
IN
= 2.7 V
20
A
V
CC
= max, V
IN
= 7.0 V
0.1
mA
I
IL
Low Level Input Current
V
CC
= max, V
IN
= 0.4 V
-0.4
mA
I
O
Output Short Circuit Current
V
CC
= max, V
O
= 0 V
(Note 1)
-20
-100
mA
I
CC
Supply Current
V
CC
= max
Outputs enabled and open
10
mA
Note 1: Not more than one output should be shorted at a time, and duration should not exceed one second.
IN74LS138
3
AC ELECTRICAL CHARACTERISTICS
(T
A
=25
C, V
CC
= 5.0 V, C
L
= 15 pF, R
L
= 2 k
, t
r
=15
ns, t
f
= 6.0 ns)
Symbol
Parameter
Level
Min
Max
Unit
t
PLH
Maximum Propagation Delay, Input A to
Output Y
2
20
ns
t
PHL
Maximum Propagation Delay, Input A to
Output Y
41
ns
t
PLH
Maximum Propagation Delay, Input A to
Output Y
3
27
ns
t
PHL
Maximum Propagation Delay, Input A to
Output Y
39
ns
t
PLH
Maximum Propagation Delay , CS1 to
Output Y
3
26
ns
t
PHL
Maximum Propagation Delay , CS1 to
Output Y
38
ns
t
PLH
Maximum Output Transition Time , CS2 or CS3
to Output Y
2
18
ns
t
PHL
Maximum Output Transition Time , CS2 or CS3
to Output Y
32
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
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