5-1

FAST AND LS TTL DATA

DUAL 1-OF-4 DECODER/

DEMULTIPLEXER

The SN54 / 74LS155 and SN54 / 74LS156 are high speed Dual 1-of-4

Decoder/Demultiplexers. These devices have two decoders with common

2-bit Address inputs and separate gated Enable inputs. Decoder “a” has an

Enable gate with one active HIGH and one active LOW input. Decoder “b” has

two active LOW Enable inputs. If the Enable functions are satisfied, one

output of each decoder will be LOW as selected by the address inputs. The

LS156 has open collector outputs for wired-OR (DOT-AND) decoding and

function generator applications.

The LS155 and LS156 are fabricated with the Schottky barrier diode

process for high speed and are completely compatible with all Motorola TTL

families.

CONNECTION DIAGRAM DIP (TOP VIEW)

NOTE:

The Flatpak version

has the same pinouts

(Connection Diagram) as

the Dual In-Line Package.

14

13

12

11

10

9

123

45

6

7

16

15

8

VCC

Ea

Eb

Eb

A0

O3b

O1b

O2b

O0b

Ea

A1

O3a

O2a

O1a

O0a GND

PIN NAMES

LOADING (Note a)

HIGH

LOW

A0, A1

Ea, Eb

Ea

O0 –O3

Address Inputs

Enable (Active LOW) Inputs

Enable (Active HIGH) Input

Active LOW Outputs (Note b)

0.5 U.L.

0.5 U.L.

0.5 U.L.

10 U.L.

0.25 U.L.

0.25 U.L.

0.25 U.L.

5 (2.5) U.L.

NOTES:

a) 1 TTL Unit Load (U.L.) = 40

µA HIGH/1.6 mA LOW.

b) The Output LOW drive factor is 2.5 U.L. for Military (54) and 5 U.L. for Commercial (74)

Temperature Ranges. The HIGH level drive for the LS156 must be established by an external

resistor.

SN54/74LS155

SN54/74LS156

DUAL 1-OF-4 DECODER /

DEMULTIPLEXER

LS156-OPEN-COLLECTOR

LOW POWER SCHOTTKY

J SUFFIX

CERAMIC

CASE 620-09

N SUFFIX

PLASTIC

CASE 648-08

16

1

16

1

ORDERING INFORMATION

SN54LSXXXJ

Ceramic

SN74LSXXXN

Plastic

SN74LSXXXD

SOIC

16

1

D SUFFIX

SOIC

CASE 751B-03

LOGIC SYMBOL

VCC = PIN 16

GND = PIN 8

1 2

13 3

14 15

EE

A0

A0

A1

A1

012

3

0

123

DECODER a

DECODER b

7

6

5

4

9

10 11 12