Fairchild FSTD16861 service manual

FSTD16861
20-Bit Bus Switch with Level Shifting

FSTD16861 20-Bit Bus Switch with Level Shifting

May 2001
Revised June 2005

General Description

The Fairchild Switch F STD16861 pr ovides 20-bits of hig h­speed CMOS TTL-compatible bus switching. The low On
Resistance of the switch allows inputs to be connected to
outputs without adding propagation delay or generating
additional ground b ounce noise. A diode to V

integrated into the circuit to allow for level shifting between
5V inputs and 3.3V outputs.

The device is organ ized as a 10-bit or 20-bit b us switch.
When OE

nected to Port 1B. When OE
to Port 2B. When OE
exists between the A and B Ports.

is LOW, the switch is ON and Port 1A is con-

1

is LOW, Port 2A is connected

2

is HIGH, a high impedance state

X

has been

CC

Features

■ 4

:

switch connection between two ports.

■ Minimal propagation delay through the switch.

■ Low l

■ Zero bounce in flow-through mode.

■ Control inputs compatible with TTL level.

■ TruTranslation

■ Power-off high impedance inputs and outputs

■ Supports live insertion/withdrawal (Note 1)

Note 1: To ensure the high-impedance state during power up or power
down, OE

value of the resistor is dete rmined by the current -sourci ng capabilit y of the
driver.

.

CC

¥

3.3V outputs

should be tied to VCC through a pull-up r esistor; the min imum

voltage translation from 5.0 V inputs to

Ordering Code:

Order Number Package Number Package Description

FSTD16861MTD MTD48 48-Lead Thin Shrink Small Outline Package (TSSOP), J EDEC MO-153, 6.1mm Wide

Devices also availab l e in Tape and Reel. Specify by appending the suffix let t er “X” to the ordering code.

TruTranslation

© 2005 Fairchild Semiconductor Corporation DS500421 www.fairchildsemi.com

¥

is trademark of Fairchild Semiconduct or C orporation.

Connection Diagram

FSTD16861

Logic Diagram

Pin Descriptions

Pin Name Description

OE

, OE

1

2

, 2A

1A

n

n

1B

, 2B

n

n

Bus Switch Enables

Bus A
Bus B

Truth Table

Inputs Inputs/Outputs

OE

LL1A
LH1A
HL Z 2A
HH Z Z

H HIGH Voltage Level
L

LOW Voltage Level
High Impedance

Z

OE

1

2

1A, 1B 2A, 2B

1B 2A 2B
1B Z

2B

www.fairchildsemi.com 2