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Semiconductor
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
SL74LS138
ORDERING INFORMATION
SL74LS138N Plastic
SL74LS138D SOIC
TA = 0° to 70° C
for all packages
PIN ASSIGNMENT
LOGIC DIAGRAM
PIN 16 =VCC
PIN 8 = GND
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
H L L
H L L
H L L
H L L
H L L
H L L
H L L
H L L
X X X
X X X
X X X
L L L
L L H
L H L
L H H
H L L
H L H
H H L
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 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
SLS
H = high level (steady state)
L = low level (steady state)
X = don’t care
System Logic
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SL74LS138
Semiconductor
MAXIMUM RATINGS*
Symbol Parameter Value Unit
VCC Supply Voltage 7.0 V
VIN Input Voltage 7.0 V
V
Output Voltage 5.5 V
OUT
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
VCC Supply Voltage 4.75 5.25 V
VIH High Level Input Voltage 2.0 V
VIL Low Level Input Voltage 0.8 V
IOH High Level Output Current -0.4 mA
IOL Low Level Output Current 8.0 mA
TA Ambient Temperature Range 0 +70 °C
DC ELECTRICAL CHARACTERISTICS over full operating conditions
Guaranteed Limit
Symbol Parameter Test Conditions Min Max Unit
VIK Input Clamp Voltage VCC = min, IIN = -18 mA -1.5 V
VOH High Level Output Voltage VCC = min, IOH = -0.4 mA 2.7 V
VOL Low Level Output Voltage VCC = min, IOL = 4 mA 0.4 V
VCC = min, IOL = 8 mA 0.5
IIH High Level Input Current VCC = max, VIN = 2.7 V 20 µA
VCC = max, VIN = 7.0 V 0.1 mA
IIL Low Level Input Current VCC = max, VIN = 0.4 V -0.4 mA
IO Output Short Circuit Current VCC = max, VO = 0 V
(Note 1)
ICC Supply Current VCC = max
Outputs enabled and open
Note 1: Not more than one output should be shorted at a time, and duration should not exceed one second.
-20 -100 mA
10 mA
System Logic
SLS
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SL74LS138
Semiconductor
AC ELECTRICAL CHARACTERISTICS (T
ns, tf = 6.0 ns)
Symbol Parameter Level Min Max Unit
t
Maximum Propagation Delay, Input A to
PLH
Output Y
t
Maximum Propagation Delay, Input A to
PHL
Output Y
t
Maximum Propagation Delay, Input A to
PLH
Output Y
t
Maximum Propagation Delay, Input A to
PHL
Output Y
t
Maximum Propagation Delay , CS1 to
PLH
Output Y
t
Maximum Propagation Delay , CS1 to
PHL
Output Y
t
Maximum Output Transition Time , CS2 or CS3
PLH
to Output Y
=25°C, VCC = 5.0 V, CL = 15 pF, RL = 2 kΩ, tr =15
A
20 ns
2
41 ns
27 ns
3
39 ns
26 ns
3
38 ns
18 ns
2
t
Maximum Output Transition Time , CS2 or CS3
PHL
32 ns
to Output Y
Figure 1. Switching Waveforms Figure 2. Switching Waveforms
SLS
NOTES A. CL includes probe and jig capacitance.
B. All diodes are 1N916 or 1N3064.
Figure 3. Switching Waveforms Figure 4. Test Circuit
System Logic
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