UCC5681PW24



                 

              



SLUS441A – MARCH 1999 – REVISED AUGUST 2000

1

POST OFFICE BOX 655303 

 DALLAS, TEXAS 75265

D

LVD-Only Active Termination

D

2.7 V to 5.25 V Operation

D

Differential Failsafe Bias

D

Built-In SPI-3 Mode Change Filter/Delay

D

Standards Supported: SPI-3, Ultra2 
(Fast 40), Ultra3/Ultra160 (Fast 80)

D

Reversed Disconnect Polarity

     

description

The UCC5681 is an LVD-only Small Computer System Interface (SCSI) terminator that integrates the mode
change delay function required by the SPI-3 specification. The device senses what types of SCSI drivers are
present on the bus via the voltage on the DIFFSENS SCSI control line. Single-ended (SE) and high-voltage
differential (HVD) SCSI drivers (EIA485) are not supported. If the chip detects the presence of an SE or HVD
SCSI driver, it disconnects itself by switching all terminating resistors off the bus and enters a high-impedance
state. The terminator can also be commanded to disconnect the terminating resistors with the DISCNCT input.
Impedance is trimmed for accuracy and maximum effectiveness. Bus lines are biased to a failsafe state to
ensure signal integrity.

The UCC5681 is offered in both 24-pin and 28-pin TSSOP (PW) packages for a temperature range of 0

°

C to

70

°

C.

functional block diagram

UDG–00126

11

12

15

100 ms

TO

300 ms

DELAY/

FILTER

DIFFB

2.15 V

0.6 V

10

µ

A

HIGH–VOLTAGE
DIFFERENTIAL

LOW–VOLTAGE
DIFFERENTIAL

SINGLE–ENDED

REF
1.3V

–15 mA

 I

SOURCE

 –5 mA

50

µ

A

 I

SINK

 200

µ

A

4

52

52

3

124

56 mV

56 mV

+   –

–   +

25

26

L1 –

L1+

L9 –

L9+

REF

1.25V

1

REG

28

TRMPWR

14

GND

DIFSENS

52

52

124

56 mV

56 mV

+   –

–   +

27

SE

LVD

HVD

DISCNCT

OPEN

DOWN

OPEN
OPEN

MODE

ALL SWITCHES

ENABLE

+

+

LVD

{

{

28-PIN PACKAGE ONLY

DISCNCT

DIS

DISCNCT

Copyright 

 2000, Texas Instruments Incorporated

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Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

UCC5681PW24 Information:
Part No.
UCC5681PW24

RFQ

Description
UCC5681PW24
File Size
210905 bytes
Page Size
612 x 792 pts (letter)
All Pages
9
Manufacturer
Texas Instruments
Homepage
http://www.ti.com/
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