DESCRIPTION

UCC5619 provides 27 lines of active termination for a SCSI (Small Com-

puter Systems Interface) parallel bus. The SCSI standard recommends ac-

tive termination at both ends of the cable.

The UCC5619 is ideal for high performance 5V SCSI systems. During dis-

connect the supply current is typically only 100

µA, which makes the IC at-

tractive for lower powered systems.

The UCC5619 is designed with a low channel capacitance of 2.5pF, which

eliminates effects on signal integrity from disconnected terminators at in-

terim points on the bus.

The power amplifier output stage allows the UCC5619 to source full termi-

nation current and sink active negation current when all termination lines

are actively negated.

The UCC5619, as with all Unitrode terminators, is completely hot pluggable

= 0V or open.

Internal circuit trimming is utilized, first to trim the 110

Ω impedance, and

then most importantly, to trim the output current as close to the maximum

SCSI-3 specification as possible, which maximizes noise margin in fast

SCSI operation.

Other features include thermal shutdown and current limit. This device is

offered in low thermal resistance versions of the industry standard 36 pin

wide body QSSOP (MWP) and 48 pin LQFP (FQP).

Consult SSOP-36 (MWP QSSOP-36) and FQP-48 Packaging Diagram for

exact dimensions.

UCC5619

27-Line SCSI Terminator With Reverse Disconnect

BLOCK DIAGRAM

FEATURES

• Complies with SCSI, SCSI-2, SCSI-3,

SPI and FAST-20 (Ultra) Standards

• 2.5pF Channel Capacitance during

Disconnect

• 100µA Supply Current in Disconnect

Mode

• 4V To 7V Operation

• 110 Termination

• Completely Meets SCSI Hot Plugging

• –900mA Sourcing Current for

Termination

• +500mA Sinking Current for Active

Negation

• Logic Command Disconnects all

Termination Lines

• Trimmed Impedance to 5%

• Current Limit and Thermal Shutdown

Protection

10/98

UDG-96108

Circuit Design Patented