UNITRODE UCC5610 Technical data

18-Line 3-5 Volt Low Capacitance SCSI Active Terminator

FEATURES DESCRIPTION

•

Complies with SCSI, SCSI-2, SCSI-3
and FAST-20 (Ultra) Standards

•

2.75V to 7V Operation

•

1.8pF Channel Capacitance during
Disconnect

•

0.5µA Supply Current in Disconnect
Mode

•

110 Ohm/2.5k Programmable
Termination

•

Completely Meets SCSI Hot Plugging

•

-650mA Sourcing Current for
Termination

•

+400mA Sinking Current for Active
Negation Drivers

•

Trimmed Termination Current to 4%

•

Trimmed Impedance to 7%

•

Current Limit and Thermal Shutdown
Protection

The UCC5610 provides 18 li nes 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 UCC5610 is ideal for high performance 3.3V SCSI systems. The key
features co ntributing to such low operating voltage are the 0.1V drop out
regulator and the 2.75V reference. The reduced reference voltage was
necessary t o accommodate the lower termin ation current dictated in the
SCSI-3 specification. During disconnect the supply current is typically
only 0.5µA, which makes the IC attractive for battery powered systems.

The UCC5610 is designed with an ultra low channel capacitance of

1.8pF, which elimina tes effects on signal i ntegrity from disconnected ter­minators at interim points on the bus.

The UCC5610 can be pr ogrammed for either a 110 ohm or 2.5k ohm ter­mination. Th e 110 ohm termination is used for standard SCSI bus lengths
and the 2 .5k ohm term ination is typical ly used in short bus applications.
When driving t he TTL compatible DISCNCT pin directly, the 110 ohm ter­mination is connected when the D ISCNCT pin is driven low, and discon­nected whe n driven high. When the DISCNCT pin is driven through an
impedance between 80k and 150k, the 2.5k ohm termination is con­nected when the DISCNCT pin is driven low, and disconnected when
driven high.

UCC5610

continued

BLOCK DIAGRAM

2/97

UDG-94128-1

Circuit Design Patented

Description Continued

The power amplifier output stage allows the UCC5610 to
source full termination current and sink active negation
current when all termination lines are actively negated.

The UCC5610 is pin for pin compatible with Unitrode’s
other 18 line SCSI terminators, allowing lower capaci­tance and lower voltage upgrades to existing systems.
The UCC5610, a s with all Unitrode terminators, is com­pletely hot pluggable and appears as high impedanc e at
the terminating channels with V

TRMPWR

Internal circuit trimming is utilized, first to trim the 110

= 0V or open.

UCC5610

ohm terminati on impedan ce to a 7% tolera nce, and then
most importantly, to trim the output current to a 4% toler­ance, as close to the max SCSI-3 spec as possible,
which maxi mizes noise margin in FAST-20 SCSI opera­tion.

Other features include thermal shutdown and current
limit.

This device i s offered in low thermal resistance versi ons
of the ind ustry standard 28 pin wide body SOIC, 24 pin
wide body DIP and 28 pin PLCC.

ABSOLUTE MAXIMUM RATINGS

Termpwr V o ltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V

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

Regulator Output Current . . . . . . . . . . . . . . . . . . Self-regulating

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

Operating Temperature . . . . . . . . . . . . . . . . . −55°C to +150°C

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

Unless otherwise specified all voltages are with respe ct to
Ground. Currents are positive into, negative out of the speci­fied terminal.
Consult Packaging Section of Unitrode Integrated Circuits dat­abook for thermal limitations and considerations of packages.

RECOMMENDED OPERATING CONDITIONS

Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . 2.75V to 5.25V

Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +5V

Disconnect Input Voltage . . . . . . . . . . . . . . . . . . 0V to Termpwr

SOIC-28 (Top View)
DWP Package

CONNECTION DIAGRAMS

PLCC-28 (Top View)
QP Package

* QP package pins 12 - 18 serve as both heatsin k and signal
ground.

DIL-24 (Top View)
N or J Package

* DWP package pin 28 serves as signal ground; pins 7, 8, 9,
20, 21, 22 serve as heatsink/ground.

Note: Drawings are not to scale.

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