UCC5618

DESCRIPTION

The UCC5618 provides 18 lines of active termination for a SCSI (Small

Computers Systems Interface) parallel bus. The SCSI standard recom-

mends and Fast-20 (Ultra) requires active termination at both ends of the

cable.

Pin for pin compatible with the UC5601 and UC5608, the UCC5618 is ideal

for high performance 5V SCSI systems, Termpwr 4.0-5.25V. During discon-

nect the supply current is only 50

µA typical, which makes the IC attractive

for lower powered systems.

The UCC5618 is designed with a low channel capacitance of 2pF, which

eliminates effects on signal integrity from disconnected terminators at in-

terim points on the bus.

The power amplifier output stage allows the UCC5618 to source full termi-

nation current and sink active negation current when all termination lines

are actively negated.

The UCC5618, as with all Unitrode terminators, is completely hot pluggable

and appears as high impedance at the terminating channels with

TRMPWR=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 max

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

eration.

This device is offered in low thermal resistance versions of the industry

standard 28 pin wide body SOIC, TSSOP and PLCC.

18-Line SCSI Terminator

FEATURES

• Complies with SCSI, SCSI-2, SCSI-3,

SPI and FAST-20 Standards

• 2pF Channel Capacitance During

Disconnect

• 50µA Supply Current in Disconnect

Mode

• 110Ω Termination

• SCSI Hot Plugging Compliant, 10nA

Typical

• +400mA Sinking Current for Active

Negation

• –650mA Sourcing Current for

Termination

• Trimmed Impedance to 5%

• Thermal Shutdown

• Current Limit

6/98

BLOCK DIAGRAM

UDG-96005-1

Patented Circuit Design