Texas Instruments UCC5621MWPTR, UCC5621MWP Datasheet

UCC5621

DESCRIPTION

UCC5621 provides 27 lines of active termination for a SCSI (Small Com­puter Systems Interface) parallel bus. The SCSI standard recommends ac­tive termination at both ends of the cable.

The UCC5621 is ideal for high performance 5V SCSI systems. During dis­connect the supply current is typically only 100µA, which makes the IC at­tractive for lower powered systems.

The UCC5621 features a split reverse disconnect allowing the user to con­trol termination lines 10 to 27 with disconnect one, DISCNCT1

, and control

terminiation lines 1 to 9 with disconnect two, DISCNCT2

.

The UCC5621 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 UCC5621 to source full termi­nation current and sink active negation current when all termination lines
are actively negated.

The UCC5621, as with all Unitrode terminators, is completely hot plugga­ble and appears as high impedance at the teminating channels with
V

TRMPWR = 0V or open.

Internal circuit trimming is utilized, first to trim the 110Ω 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 FAST­20 SCSI operation.

(continued)

27 - Line SCSI Terminator With Split 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

• 110Ω Termination

• Completely Meets SCSI Hot Plugging

• –900mA Sourcing Current for

Termination

• +500mA Sinking Current for Active
Negation

• Logic Command Disconnects all
Termination Lines

• Split Reverse Controls Lines 1 to 9
and 10 to 27 Separately

• Trimmed Impedance to 5%

• Current Limit and Thermal Shutdown

Protection

10/98

UDG-96111

Circuit Design Patented

2

UCC5621

ABSOLUTE MAXIMUM RATINGS

TRMPWR Voltage................................+7V

Signal Line Voltage ..........................0Vto+7V

Regulator Output Current ..........................1.5A

Storage Temperature ...................-65°C to +150°C

Junction Temperature...................-55°C to +150°C

Lead Temperature (Soldering, 10 Sec.).............+300°C

Currents are positive into, negative out of the specified terminal.
Consult Packaging Section of Databook for thermal limitations
and considerations of packages.

CONNECTION DIAGRAM

QSOP-44 (Top View)
MWP Package

ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for T

A

= 0°C to 70°C,

TRMPWR = 4.75V, DISCNCT1 = DSCNCT2 = 4.75V, TA=TJ.

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Supply Current Section

TRMPWR Supply Current All Termination Lines = Open 1 2 mA

All Termination Lines = 0.2V 630 650 mA

Power Down Mode DISCNCT1

= DSCNCT2 = 0V 100 200 µA

Other features include thermal shutdown and current
limit. This device is offered in low thermal resistance ver­sions of the industry standard 44 pin wide body QSOP
(MWP) and 48 pin LQFP. Consult QSOP-44 and FQP-48
Packaging Diagrams for exact dimensions.

DESCRIPTION (cont.)

LQFP-48 (Top View)
FQP Package