UCC5641

SLUS397 - JANUARY 2000

FEATURES

• First LVD only Active Terminator

• Meets SCSI SPI-2 Ultra2 (Fast-40)

and Ultra3 / Ultra160 (Fast-80)

Standards

• 2.7V to 5.25V Operation

• Differential Failsafe Bias

• Reversed Disconnect Polarity

Low Voltage Differential (LVD) SCSI 9 Line Terminator

REF 1.25V

15

DISCNCT

27

LVD*

1

REG

11

DIFFB

4

L1–

3

L1+

26

L9–

25

L9+

56mV

SOURCE/SINK REGULATOR

REF 1.3V

1.3V

± 0.1V

0.7V > 0.5V

2.4V > 1.9V

HIGH IMPEDANCE RECEIVER

EVEN WITH POWER OFF

SINGLE

ENDED

HIGH POWER

DIFFERENTIAL

12

DIFSENS

SOURCE 5–15mA

SINK 200

µAMAXIMUM (NOISELOAD)

OPEN CIRCUIT ON POWER OFF

OR OPEN CIRCUIT IN A

DISABLED TERMINATOR MODE

10

µA

28

TRMPWR

LOW

FREQUENCY

FILTER

50Hz – 60Hz

20k

124

124

52

52

52

52

4.7

µF

0.1

µF

14

GND

SOURCE ONLY FROM TRMPWR AND THE ENABLED TERMINATIONS

2.7V to 5.25V

56mV

+–

–+

56mV

+–

56mV

–+

BLOCK DIAGRAM

UDG-99160

DESCRIPTION

The UCC5641 is an active terminator for Low Voltage Differential (LVD)

SCSI networks. This LVD only design allows the user to reach peak bus

performance while reducing system cost. The device is designed as an

active Y-terminator to improve the frequency response of the LVD Bus.

Designed with a 1.5pF channel capacitance, the UCC5641 allows for mini-

mal bus loading for a maximum number of peripherals. With the

UCC5641, the designer will be able to comply with the Fast-40 SPI-2 and

Fast-80 SPI-3 specifications. The UCC5641 also provides a much-needed

system migration path for ever improving SCSI system standards. This de-

vice is available in the 24 pin TSSOP and 28 pin TSSOP for ease of lay-

out use.

The UCC5641 is not designed for use in single ended or high voltage dif-

ferential systems.

* 28 pin package only