© 2005 Fairchild Semiconductor Corporation

DS500044

www.fairchildsemi.com

August 1997

Revised January 2005

FST3126

4-Bit Bus Switch

General Description

The Fairchild Switch FST3126 provides four high-speed

CMOS TTL-compatible bus switches. The low on resis-

tance of the switch allows inputs to be connected to out-

puts without adding propagation delay or generating

additional ground bounce noise.

The device is organized as four 1-bit switches with sepa-

rate OE inputs. When OE is HIGH, the switch is ON and

Port A is connected to Port B. When OE is LOW, 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:

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

Logic Diagram

Pin Descriptions

Connection Diagrams

Pin Assignment for SOIC and TSSOP

Pin Assignment for QSOP

Truth Table

Order Number

Package Number

Package Description

FST3126M

M14A

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

FST3126QSC

MQA16

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

FST3126MTC

MTC14

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

Pin Name

Description

Bus Switch Enables

1A, 2A, 3A, 4A

Bus A

1B, 2B, 3B, 4B

Bus B

NC

Not Connected

Inputs

Inputs/Outputs

OE

A,B

LZ

HA

= B