© 2001 Fairchild Semiconductor Corporation

DS500472

www.fairchildsemi.com

August 2001

Revised September 2001

FST32253

Dual 4:1 Multiplexer/Demultiplexer Bus Switch

with 25

Ω Series Resistor in Outputs

General Description

The Fairchild Switch FST32253 is a dual 4:1 high-speed

CMOS

TTL-compatible

multiplexer/demultiplexer

bus

switch. The low On Resistance of the switch allows inputs

to be connected to outputs without adding propagation

delay or generating additional ground bounce noise.

selected B Port output. When OE is HIGH, the switch is

OPEN and a high-impedance state exists between the two

ports.

The FST32253 has an equivalent 25

Ω series resistor to

reduce signal-reflection noise, eliminating the need for

external terminating resistors.

Features

s 25

Ω switch connection between two ports

s Minimal propagation delay through the switch

s Zero bounce in flow-through mode

s Control inputs compatible with TTL level

Ordering Code:

Device also available in Tape and Reel. Specify by appending suffix letter “X” to the ordering code.

Logic Diagram

Pin Descriptions

Connection Diagram

Truth Table

Order Number

Package Number

Package Description

FST32253M

M16A

16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150" Narrow

FST32253QSC

MQA16

16-Lead Quarter Size Outline Package (QSOP), JEDEC MO-137, 0.150" Wide

FST32253MTC

MTC16

16-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide

Pin Name

Description

Bus Switch Enables

Select Inputs

ABus A

Bus B

Function

X

X

H

X

Disconnect 1A

X

X

X

H

Disconnect 2A

L

LLL

A

= B

1

LH

L

L

A

= B

2

H

LLL

A

= B

3

HH

L

L

A

= B

4