TECHNICAL DATA
IN74AC138
1-of-8 Decoder/Demultiplexer
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
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
X X H
X H X
L X X
H
H
H
H
PIN 16 =V
CC
PIN 8 = GND
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
H = high level (steady state)
L = low level (steady state)
X = don’t care
Rev. 00
IKSEMICON [ IK SEMICON CO., LTD ]
