5

UCC5630A

REG

TERMPWR

DISCNCT

TERMPWR

DIFFB

REG

DIFF B

TERMPWR

TERMPWR

4.7

4.7

4.7

4.7

µF

4.7

36

17

20

1

21

20

21

1

CONTROL LINES

36

DISCNCT 17

CONTROL LINES

DIFSENS

DIFSENS

REG

TERMPWR

DISCNCT

DIFF B

4.7

36

17

1

21

DATA LINES (9)

REG

TERMPWR

DIFFB

4.7

36

19

1

21

DATA LINES (9)

TERMPWR

REG

DIFFB

4.7

µF

21

1

DATA LINES (9)

36

DISCNCT 17

TERMPWR

REG

DIFFB

4.7

µF

21

1

DATA LINES (9)

36

DISCNCT 17

4.7

MSTR/SLV

19

19

MSTR/SLV

19

MSTR/SLV

19

MSTR/SLV

MSTR/SLV

19

DISCNCT

17

MSTR/SLV

50k

50k

20

20

20

20 NC

NC

NC

NC

APPLICATION INFORMATION

Figure 2. Application diagram.

UDG-98193

All SCSI buses require a termination network at each

end to function properly. Specific termination require-

ments differ, depending on which types of SCSI devices

are present on the bus.

The UCC5630A is used in multi-mode active termination

applications, where single ended (SE) and low voltage

differential (LVD) devices might coexist. The UCC5630A

has both SE and LVD termination networks integrated

into a single monolithic component. The correct termina-

tion network is automatically determined by the SCSI bus

"DIFSENS" signal.

The SCSI bus DIFSENS signal line is used to identify

which types of SCSI devices are present on the bus. On

power-up, the UCC5630A DIFSENS drivers will try to de-

liver 1.3V to the DIFSENS line. If only LVD devices are

present, the DIFSENS line will be successfully driven to

1.3V and the terminators will configure for LVD operation.

If any single ended devices are present, they will present

a short to ground on the DIFSENS line, signaling the

UCC5630A(s) to configure into the SE mode, accommo-

dating the SE devices. Or, if any high voltage differential

(HVD) devices are present, the DIFSENS line is pulled

high and the terminator will enter a high impedance

state, effectively disconnecting from the bus.