HIT HD74ACT139, HD74AC139 Datasheet
HD74AC139/HD74ACT139
Dual 1-of-4 Decoder/Demultiplexer
Description
The HD74AC139/HD74ACT139 is a high-speed, dual 1-of-4 decoder/demultiplexer. The device has two
independent decoders, each accepting two inputs and providing four mutually-exclusive active-Low
outputs. Each decoder has an active-Low Enable input which can be used as a data input for a 4-output
demultiplexer. Each half of the HD74AC139/HD74ACT139 can be used as a function generator providing
all four minterms of two variables.
Features
• Multifunction Capability
• Two Completely Independent 1-of-4 Decoders
• Active Low Mutually Exclusive Outputs
• Outputs Source/Sink 24 mA
• HD74ACT139 has TTL-Compatible Inputs
HD74AC139/HD74ACT139
Pin Arrangement
Logic Symbol
1
a
E
A0a
2
A1a
3
O0a
4
O1a
5
O2a
6
7
O3a
GND
8
A0EA1
(Top view)
CC
V
16
Eb
15
14
A0b
13
A1b
O0b
12
O1b
11
O2b
10
9
O3b
A0EA1
Pin Names
A0, A
E Enable Inputs
O0 to O 3Outputs
2
Address Inputs
1
DECODER a
O
0
O1O2O3
DECODER b
O
0
O1O2O3
HD74AC139/HD74ACT139
Logic Diagram
Ea EbA0a A1a A0b A1b
O3bO2bO1bO0bO3aO2aO1aO0a
Please note that this diagram is provided only for the understanding of logic operations and should not be
used to estimate propagation delays.
Functional Description
The HD74AC139/HD74ACT139 is a high-speed dual 1-of-4 decoder/demultiplexer. The device has two
independent decoders, each of which accepts two binary weighted inputs (A0 to A1) and provides four
mutually exclusive active-Low outputs (O0 to O3). Each decoder has an active-Low enable (E). When E is
High all outputs are forced High. The enable can be used as the data input for a 4-output demultiplexer
application. Each half of the HD74AC139/HD74ACT139 generates all four minterms of two variables.
These four minterms are useful in some applications, replacing multiple gate functions as shown in Figure
a, and thereby reducing the number of packages required in a logic network.
Truth Table
Inputs Outputs
E A
0
A
1
HXX HHHH
LL L L H H H
LH L H L H H
LLHHHL H
LHHHHHL
H : High Voltage Level
L : Low Voltage Level
X : Immaterial
O
0
O
1
O
2
O
3
3
Loading...