UCC5620

DESCRIPTION

UCC5620 provides 27 lines of active termination for a SCSI (Small Com-

puter Systems Interface) parallel bus. The SCSI standard recommends

active termination at both ends of the cable.

The UCC5620 is ideal for high performance 5V SCSI systems. During

disconnect the supply current is typically only 100

µA, which makes the IC

attractive for lower powered systems.

The UCC5620 is designed with a low channel capacitance of 2.5pF,

which eliminates effects on signal integrity from disconnected terminators

at interim points on the bus.

The power amplifier output stage allows the UCC5620 to source full ter-

mination current and sink active negation current when all termination

lines are actively negated.

The UCC5620, as with all Unitrode terminators, is completely hot plugga-

ble and appears as high impedance at the teminating channels with

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 QSOP (MWP) and 48-Pin LQFP (FQP).

Consult QSOP-36 or LQFP-48 packaging diagram for exact dimensions.

27-Line SCSI Terminator

BLOCK DIAGRAM

FEATURES

• Complies with SCSI, SCSI-2, SCSI-3,

SPI and FAST-20 (Ultra) Standards

• 2.5pF Channel Capacitance during

Disconnect

• 100mA 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

SLUS287A - OCTOBER 1999

UDG-96109

Circuit Design Patented