MOTOROLA

SEMICONDUCTOR TECHNICAL DATA

1

REV 6

10/95

1-of-8 Decoder/Demultiplexer

with LSTTL Compatible Inputs

High–Performance Silicon–Gate CMOS

The MC74HCT138A is identical in pinout to the LS138. The HCT138A

may be used as a level converter for interfacing TTL or NMOS outputs to

High Speed CMOS inputs.

The HCT138A decodes a three–bit Address to one–of–eight active–lot

outputs. This device features three Chip Select inputs, two active–low and

one active–high to facilitate the demultiplexing, cascading, and chip–select-

ing 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.

• Output Drive Capability: 10 LSTTL Loads

• TTL/NMOS Compatible Input Levels

• Outputs Directly Interface to CMOS, NMOS, and TTL

• Operating Voltage Range: 4.5 to 5.5 V

• Low Input Current: 1.0 µA

• In Compliance with the Requirements Defined by JEDEC Standard

No. 7A

• Chip Complexity: 122 FETs or 30.5 Equivalent Gates

LOGIC DIAGRAM

7

Y6

Y5

Y4

Y3

Y2

Y1

Y0

Y7

9

10

11

12

13

14

15

3

2

1

CS1

CS2

A0

A1

A2

ACTIVE–LOW

OUTPUTS

ADDRESS

INPUTS

CS3

CHIP–

SELECT

INPUTS

5

4

6

PIN 16 = VCC

PIN 8 = GND

Design Criteria

Value

Units

Internal Gate Count*

30.5

ea.

Internal Gate Propagation Delay

1.5

ns

Internal Gate Power Dissipation

5.0

µW

Speed Power Product

.0075

pJ

*Equivalent to a two–input NAND gate.

MC74HCT138A

PIN ASSIGNMENT

13

14

15

16

9

10

11

12

5

4

3

2

1

8

7

6

A0

CS2

A2

A1

Y7

CS1

CS3

GND

Y3

Y2

Y1

Y0

VCC

Y5

Y4

Y6

D SUFFIX

SOIC PACKAGE

CASE 751B–05

N SUFFIX

PLASTIC PACKAGE

CASE 648–08

ORDERING INFORMATION

MC74HCTXXXAN

MC74HCTXXXAD

MC74HCTXXXADT

Plastic

SOIC

TSSOP

1

16

1

16

1

16

DT SUFFIX

TSSOP PACKAGE

CASE 948F–01

Inputs

Outputs

CS1CS2 CS3 A2 A1 A0 Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7

X

X

H

X

X

X

H

H

H

H

H

H

H

H

X

H

X

X

X

X

H

H

H

H

H

H

H

H

L

X

X

X

X

X

H

H

H

H

H

H

H

H

H

L

L

L

L

L

L

H

H

H

H

H

H

H

H

L

L

L

L

H

H

L

H

H

H

H

H

H

H

L

L

L

H

L

H

H

L

H

H

H

H

H

H

L

L

L

H

H

H

H

H

L

H

H

H

H

H

L

L

H

L

L

H

H

H

H

L

H

H

H

H

L

L

H

L

H

H

H

H

H

H

L

H

H

H

L

L

H

H

L

H

H

H

H

H

H

L

H

H

L

L

H

H

H

H

H

H

H

H

H

H

L

FUNCTION TABLE

H = high level (steady state)

L = low level (steady state)

X = don’t care