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
• Schott ky Clampe d for High Perfor manc e
IN74LS138
ORDERING INFORMATION
IN74LS138N Plastic
IN74LS138D SOIC
TA = 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 (s t eady stat e)
L = low level (steady state)
X = don’t care
LOGIC DIAGRAM
PIN 16 =VCC
PIN 8 = GND
IN74LS138
2
MAXIMUM RATINGS*
Symbol Parameter Value Unit
VCC Supply Voltage 7.0 V
VIN Input Voltage 7.0 V
VOUT 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
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 O utput Current 8.0 mA
TAAmbient Temperature Range 0 +70 °C
DC ELECTRICAL CHARACTERISTICS over full operating conditions
Guaranteed Limit
Symbol Parameter Test Conditions Min Ma x Unit
VIK Input Clamp Vo ltage VCC = min, IIN = -18 mA -1.5 V
VOH High Level Output Vo ltage 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 Curr ent 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
IOOutput Short Circuit Current VCC = max, VO = 0 V
(Note 1) -20 -100 mA
ICC Supply Current VCC = 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 (TA=25°C, VCC = 5.0 V, CL = 15 pF, RL = 2 kΩ, tr =15
ns, tf = 6.0 ns)
Symbol Parameter Level Min Max Unit
tPLH Maximum P r o pagation Delay, Input A to
Output Y 2 20 ns
tPHL Maximum Propagation Delay, Input A to
Output Y 41 ns
tPLH Maximum P r o pagation Delay, Input A to
Output Y 3 27 ns
tPHL Maximum Propagation Delay, Input A to
Output Y 39 ns
tPLH Maximum Propagation Delay , CS1 to
Output Y 3 26 ns
tPHL Maximum Propagation Delay , CS1 to
Output Y 38 ns
tPLH Maximum Output T ransition Time , CS2 or CS3
to Output Y 2 18 ns
tPHL Maximum Output Transition Time , CS2 or CS3
to Output Y 32 ns
Figure 1. Switching Waveforms Figure 2. Switching Waveforms
NOTES A. CL includes probe and jig capacitance.
B. All diodes are 1N916 or 1N3064.
Figure 3. Switching Waveforms Figure 4. Test Circuit
