© 1999 Fairchild Semiconductor Corporation

DS500057

www.fairchildsemi.com

September 1997

Revised December 1999

FST3257

Quad 2:1 Multiplexer/Demultiplexer Bus Switch

General Description

The Fairchild Switch FST3257 is a quad 2:1 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.

When OE is LOW, the select pin connects the A Port to the

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

OPEN and a high-impedance state exists between the two

ports.

Features

s 4

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

FST3257M

M16A

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

FST3257QSC

MQA16

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

FST3257MTC

MTC16

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

Pin Name

Description

OE

Bus Switch Enable

S

Select Input

ABus A

Bus B

SOE

Function

X

H

Disconnect

LL

A

= B

1

HL

A

= B

2