HIT HD74AC539 Datasheet

HD74AC539

Dual 1-of-4 Decoder with 3-State Output

Description

The HD74AC539 contains two inpedendent decoders. Each accepts two Address (A0, A1) input signals and
decodes them to select one of four mutually exclusive outputs. A polarity control input (P) determines
whether the outputs are active HIGH (P = L) or active LOW (P = H). An active LOW input Enable (E) is
available for data demultiplexing; data is routed to the selected output in non-inverted form in the active
LOW mode or in inverted form in the active HIGH mode. A HIGH signal on the active LOW Output
Enable (OE) input forces the 3-state outputs to the high impedance state.

Feature

• Outputs Source/Sink 24 mA

HD74AC539

Pin Arrangement

O2b

1

20

V

CC

Logic Symbol

2

O1b

O0b

3

Pb

4

OEb

5

A0a

6

7

A1a

O3a

8

O2a

9

GND

10 11

(Top view)

19

18

17

16

15

14

13

12

O3b

A1b

A0b

Eb

Ea

OE

Pa

O0d

O1a

a

P

A0

A1

E

DECODER a

OE

O0 O1 O2 O3

2

P

A0

E

DECODER b

OE

O0 O1 O2 O3

A1

Pin Names

HD74AC539

A0a to A
A0b to A

Ea – E

b

OEa, OE

Pa, P

b

O0a to O
O0b to O

1a

1b

b

3a

3b

Side A Address Inputs
Side B Address Inputs
Enable Inputs (Active LOW)
Output Enable Inputs (Active LOW)
Polarity Control Inputs
Side A 3-State Outputs
Side B 3-State Outputs

Truth Table

Inputs Outputs

Function OE E A

1

A

0

High impedance H X X X ZZZZ
Disable L H X X On = P
Active HIGH output LLLLHLLL
(P = L) LLLHLHLL

LLHLLLHL

LLHHLLLH
Active LOW output LLLLLHHH
(P = H) LLLHHLHH

LLHLHHLH

LLHH HHHL
H : High Voltage Level

L : Low Voltage Level
X : Immaterial
Z : High Impedance

O

0

O

1

O

2

O

3

3