74AC139 FAIRCHILD [Fairchild Semiconductor], 74AC139 Datasheet - Page 2

• Manufacturer Part Number: 74AC139
• Description: Dual 1-of-4 Decoder/Demultiplexer
• Manufacturer: FAIRCHILD [Fairchild Semiconductor]

www.fairchildsemi.com
Logic Symbols
Truth Table
H
L
X
HIGH Voltage Level
LOW Voltage Level
E
H
Immaterial
L
L
L
L
Inputs
A
H
H
X
L
L
0
A
H
H
X
L
L
1
IEEE/IEC
O
H
H
H
H
L
0
O
H
H
H
H
L
Outputs
1
O
H
H
H
H
L
2
O
H
H
H
H
L
3
2
Functional Description
The AC/ACT139 is a high-speed dual 1-of-4 decoder/
demultiplexer. The device has two independent decoders,
each of which accepts two binary weighted inputs (A
and provides four mutually exclusive active-LOW outputs
(O
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 AC/ACT139 generates all four
minterms of two variables. These four minterms are useful
in some applications, replacing multiple gate functions as
shown in Figure 1, and thereby reducing the number of
packages required in a logic network.
Logic Diagram
Please note that this diagram is provided only for the understanding of logic
operations and should not be used to estimate propagation delays.
0
–O
3
). Each decoder has an active-LOW enable (E).
FIGURE 1. Gate Functions (Each Half)
0
–A
1
)