TEXAS INSTRUMENTS CD74AC238 Technical data

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CD74AC238

3-LINE TO 8-LINE DECODER/DEMULTIPLEXER

SCHS331 – FEBRUARY 2003

D

AC Types Feature 1.5-V to 5.5-V Operation
and Balanced Noise Immunity at 30% of the

M PACKAGE

(TOP VIEW)

Supply Voltage

D

Speed of Bipolar F, AS, and S, With
Significantly Reduced Power Consumption

D

Designed Specifically for High-Speed
Memory Decoders and Data-Transmission
Systems

D

Incorporates Three Enable Inputs to
Simplify Cascading and/or Data Reception

D

Balanced Propagation Delays

D

±24-mA Output Drive Current

G

2A

G

2B

G1

Y7

GND

A

1
2

B

3

C

4
5
6
7
8

16
15
14
13
12
11
10

V

CC

Y0
Y1
Y2
Y3
Y4
Y5

9

Y6

– Fanout to 15 F Devices

D

SCR-Latchup-Resistant CMOS Process and
Circuit Design

D

Exceeds 2-kV ESD Protection Per
MIL-STD-883, Method 3015

description/ordering information

The CD74AC238 decoder/demultiplexer is designed for high-performance memory-decoding and data-routing
applications that require very short propagation-delay times. In high-performance memory systems, this
decoder can be used to minimize the effects of system decoding. When employed with high-speed memories
utilizing a fast enable circuit, the delay times of this decoder and the enable time of the memory usually are less
than the typical access time of the memory. This means that the effective system delay introduced by the
decoder is neg ligible.

The conditions at the binary-select inputs and the three enable inputs select one of eight output lines. Two
active-low and one active-high enable inputs reduce the need for external gates or inverters when expanding.
A 24-line decoder can be implemented without external inverters, and a 32-line decoder requires only one
inverter. An enable input can be used as a data input for demultiplexing applications (see Application
Information).

ORDERING INFORMATION

T

A

–55°C to 125°C SOIC – M Tape and reel CD74AC238M96 AC238M

†

Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines
are available at www.ti.com/sc/package.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PACKAGE

†

ORDERABLE

PART NUMBER

TOP-SIDE
MARKING

PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

Copyright  2003, Texas Instruments Incorporated

1

CD74AC238
3-LINE TO 8-LINE DECODER/DEMULTIPLEXER

SCHS331 – FEBRUARY 2003

FUNCTION TABLE

ENABLE INPUTS SELECT INPUTS OUTPUTS

G1 G2A G2B C B A Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7

X H X X X X L L L L L L L L
X XHXXXLLLLLLLL
L XXXXXLLLLLLLL
H LLLLLHLLLLLLL
H LLLLHLHLLLLLL
H LLLHLLLHLLLLL
H LLLHHL LLHLLLL
H LLHLLLLLLHLLL
H LLHLHLLLLLHLL
H LLHHLLLLLLLHL
H L L H H H L L L L L L L H

logic diagram (positive logic)

1

A

15

14

Y0

Y1

Select
Inputs

Enable

Inputs

13

12

11

10

Y2

Y3

Data

Y4

Y5

9

Y6

7

Y7

Outputs

2

B

3

C

4

2A

G

5

G

2B

6

G1

2

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

∆t/∆v

Input transition rise or fall rate

ns/V

CD74AC238

3-LINE TO 8-LINE DECODER/DEMULTIPLEXER

SCHS331 – FEBRUARY 2003

absolute maximum ratings over operating free-air temperature range (unless otherwise noted)

Supply voltage range, V
Input clamp current, I
Output clamp current, I
Continuous output current, I
Continuous current through V
Package thermal impedance, θ
Storage temperature range, T

†

Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

NOTES: 1. The input and output voltage ratings may be exceeded if the input and output current ratings are observed.

2. The package thermal impedance is calculated in accordance with JESD 51-7.

–0.5 V to 6 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CC

(VI < 0 V or VI > VCC) (see Note 1) ±20 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

IK

(VO < 0 V or VO > VCC) (see Note 1) ±50 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OK

(VO > 0 V or VO < VCC) ±50 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

O

or GND ±200 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CC

(see Note 2) 73°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

JA

–65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

stg

†

recommended operating conditions (see Note 3)

TA = 25°C
MIN MAX MIN MAX MIN MAX

V

V

V

V
V
I

OH

I

OL

NOTE 3: All unused inputs of the device must be held at VCC or GND to ensure proper device operation. Refer to the TI application report,

Supply voltage 1.5 5.5 1.5 5.5 1.5 5.5 V

CC

VCC = 1.5 V 1.2 1.2 1.2

High-level input voltage

IH

Low-level input voltage

IL

Input voltage 0 V

I

Output voltage 0 V

O

High-level output current VCC = 4.5 V to 5.5 V –24 –24 –24 mA
Low-level output current VCC = 4.5 V to 5.5 V 24 24 24 mA

p

Implications of Slow or Floating CMOS Inputs, literature number SCBA004.

VCC = 3 V 2.1 2.1 2.1
VCC = 5.5 V 3.85 3.85 3.85
VCC = 1.5 V 0.3 0.3 0.3
VCC = 3 V
VCC = 5.5 V 1.65 1.65 1.65

VCC = 1.5 V to 3 V 50 50 50
VCC = 3.6 V to 5.5 V 20 20 20

–55°C to

125°C

0.9 0.9 0.9

CC
CC

0 V
0 V

CC
CC

–40°C to

85°C

0 V
0 V

CC
CC

UNIT

V

V

V
V

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

3

CD74AC238

CC

(INPUT)

(OUTPUT)

A, B, C

Any Y

ns

G1

Any Y

ns

G2A, G2B

Any Y

ns

3-LINE TO 8-LINE DECODER/DEMULTIPLEXER

SCHS331 – FEBRUARY 2003

electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)

PARAMETER TEST CONDITIONS V

1.5 V 1.4 1.4 1.4

IOH = –50 µA

V

OH

V

OL

I

I

I

CC

C

†

i

T est one output at a time, not exceeding 1-second duration. Measurement is made by forcing indicated current and measuring voltage to minimize
power dissipation. T est verifies a minimum 50-Ω transmission-line drive capability at 85°C and 75-Ω transmission-line drive capability at 125°C.

VI = VIH or V

VI = VIH or V

VI = VCC or GND 5.5 V ±0.1 ±1 ±1 µA
VI = VCC or GND, IO = 0 5.5 V 8 160 80 µA

IL

IL

IOH = –4 mA 3 V 2.58 2.4 2.48
IOH = –24 mA 4.5 V 3.94 3.7 3.8
IOH = –50 mA
IOH = –75 mA

IOL = 50 µA

IOL = 12 mA 3 V 0.36 0.5 0.44
IOL = 24 mA 4.5 V 0.36 0.5 0.44
IOL = 50 mA
IOL = 75 mA

†
†

†
†

3 V 2.9 2.9 2.9

4.5 V 4.4 4.4 4.4

5.5 V 3.85

5.5 V 3.85

1.5 V 0.1 0.1 0.1
3 V 0.1 0.1 0.1

4.5 V 0.1 0.1 0.1

5.5 V 1.65

5.5 V 1.65

TA = 25°C
MIN MAX MIN MAX MIN MAX

–55°C to

125°C

10 10 10 pF

–40°C to

85°C

UNIT

V

V

switching characteristics over recommended operating free-air temperature range,
V

= 1.5 V, CL = 50 pF (unless otherwise noted) (see Figure 1)

CC

PARAMETER

t

PLH

t

PHL

t

PLH

t

PHL

t

PLH

t

PHL

FROM

TO

–55°C to

125°C

MIN MAX MIN MAX

187 170
187 170
208 189
208 189
149 135
149 135

–40°C to

85°C

UNIT

4

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265