IN74AC138
1-
OF
-8 D
ECODER
/D
EMULTIPLEXER
High-Speed Silicon-Gate CMOS
The IN74AC138 is identical in pinout to the LS/ALS138,
HC/HCT138. The device inputs are compatible with standard
CMOS outputs; with pullup resistors, they are compatible with
LS/ALS outputs.
The IN74AC138 decodes a three-bit Address to one-of-eight
active-low outputs. This device features three Chip Select
inputs, two active-low and one active-high to facilitate the
demultiplexing, cascading, and chip-selecting functions. The
demultiplexing function is accomplished by using the Address
inputs to select the desired device output; one of the Chip
Selects is used as a data input while the other Chip Selects are
held in their active states.
Outputs Directly Interface to CMOS, NMOS, and TTL
Operating Voltage Range: 2.0 to 6.0 V
Low Input Current: 1.0
µA;
0.1
µA
@ 25°C
High Noise Immunity Characteristic of CMOS Devices
Outputs Source/Sink 24 mA
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ORDERING INFORMATION
IN74AC138N Plastic
IN74AC138D SOIC
T
A
= -40° to 85° C for all
packages
PIN ASSIGNMENT
LOGIC DIAGRAM
FUNCTION TABLE
Inputs
CS1 CS2 CS3 A2 A1 A0
X X H
X X X
X H X
X X X
L X X
X X X
H L L
L L L
H L L
L L H
H L L
L H L
H L L
L H H
H L L
H L L
H L L
H L H
H L L
H H L
H L L
H H 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
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