© 2000 Fairchild Semiconductor Corporation

DS500302

www.fairchildsemi.com

August 1999

Revised April 2000

FSTU3257

Quad 2:1 Multiplexer/Demultiplexer Bus Switch

with

−2V Undershoot Protection

General Description

The Fairchild Switch FSTU3257 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. The A and B Ports are “undershoot

hardened” with UHC

 protection to support an extended

range of 2.0V below ground. Fairchild’s integrated Under-

shoot Hardened Circuit UHC senses undershoot at the I/O

and responds by preventing voltage differentials from

developing and turning on the switch. When OE is HIGH,

the switch is OPEN and a high-impedance state exists

between the two ports.

Features

s Undershoot hardened to

−2V (A and B Ports)

s Soft enable turn-on to minimize bus to bus charge

sharing during enable

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.

s See Applications Note AN-5008 for details

Ordering Code:

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

UHC

 is a trademark of Fairchild Semiconductor Corporation.

Order Number

Package Number

Package Description

FSTU3257M

M16A

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

FSTU3257QSC

MQA16

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

FSTU3257MTC

MTC16

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