2

Description

The Harris CD74HC138, CD74HC238 and CD74HCT138,

CD74HCT238 are high speed silicon gate CMOS decoders

well suited to memory address decoding or data routing

applications. Both circuits feature low power consumption

usually associated with CMOS circuitry, yet have speeds

comparable to low power Schottky TTL logic. Both circuits

have three binary select inputs (A0, A1 and A2). If the device

is enabled, these inputs determine which one of the eight

normally high outputs of the HC/HCT138 series will go low

or which of the normally low outputs of the HC/HCT238

series will go high.

Two active low and one active high enables (E1, E2, and E3)

are provided to ease the cascading of decoders. The

decoder’s 8 outputs can drive 10 low power Schottky TTL

equivalent loads.

Functional Diagram

Ordering Information

PART NUMBER

PACKAGE

PKG.

NO.

CD74HC138E

-55 to 125

16 Ld PDIP

E16.3

CD74HCT138E

-55 to 125

16 Ld PDIP

E16.3

CD74HC238E

-55 to 125

16 Ld PDIP

E16.3

CD74HCT238E

-55 to 125

16 Ld PDIP

E16.3

CD74HC138M

-55 to 125

16 Ld SOIC

M16.15

CD74HCT138M

-55 to 125

16 Ld SOIC

M16.15

CD74HC238M

-55 to 125

16 Ld SOIC

M16.15

CD74HCT238M

-55 to 125

16 Ld SOIC

M16.15

CD74HC138SM

-55 to 125

16 Ld SSOP

M16.209

NOTES:

1. When ordering, use the entire part number. Add the suffix 96 to

obtain the variant in the tape and reel.

2. Wafer and die for this part number is available which meets all

electrical specifications. Please contact your local sales office or

Harris customer service for ordering information.

Ordering Information

PART NUMBER

PACKAGE

PKG.

NO.

TRUTH TABLE CD74HC138, CD74HCT138

INPUTS

OUTPUTS

ENABLE

ADDRESS

E3

E2

E1

A2

A1

A0

Y0

Y1

Y2

Y3

Y4

Y5

Y6

Y7

X

X

H

X

X

X

HHHHHHHH

L

XXXXX

H

H

H

H

H

H

H

H

X

H

X

X

X

X

HHHHHHHH

H

L

LLLLL

H

H

H

H

H

H

H

HL

L

L

LH

HLH

H

H

H

H

H

HL

L

L

HLH

HLH

H

H

H

H

H

L

L

L

HHHHH

L

HHHH

15

14

13

12

10

7

9

11

1

2

3

5

6

4

E3

E2

E1

A2

A1

A0

Y0

Y7

Y6

Y5

Y4

Y3

Y2

Y1

Y0

Y7

Y6

Y5

Y4

Y3

Y2

Y1

HC/HCT

238

HC/HCT

138

CD74HC138, CD74HCT138, CD74HC238, CD74HCT238