UNITRODE UCC5618 Technical data

18-Line SCSI Terminator

UCC5618

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

DESCRIPTION

The UCC5618 provides 18 lines of active termination for a SCSI (Small
Computers Systems Interface) parallel bus. The SCSI standard recom­mends 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 discon­nect the supply current is only 50µA 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 in­terim points on the bus.

The power amplifier output stage allows the UCC5618 to source full termi­nation 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 110Ω 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 op­eration.

BLOCK DIAGRAM

This device is offered in low thermal resistance versions of the industry
standard 28 pin wide body SOIC, TSSOP and PLCC.

Patented Circuit Design

6/98

UDG-96005-1

ABSOLUTE MAXIMUM RATINGS

TEMPWR.......................................+7V

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

Regulator Output Current ...........................1A

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

Operating Junction Temperature ..........–55°C to +150°C

Lead Temperature (Soldering, 10 Seconds) ..........300°C

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

CONNECTION DIAGRAMS

UCC5618

PLCC-28 (Top View)
QP Package

* DWP package pins 12–18 serve as both heatsink and signal
ground.

DIL-24 (Top View)
N Package

TSSOP-28 (Top View)
PWP Package

* PWP package pin 23 serves as signal ground; pins 7, 8, 9,
20, 21, and 22 serve as heatsink ground.

SOIC-28 (Top View)
DWP Package

Note: Drawings are not to scale.

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

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UCC5618

ELECTRICAL CHARACTERISTICS:

Unless otherwise stated these specifications apply for TA= 0°C to 70°C,

TRMPWR = 4.75V, DISCNCT = 0V, TA=TJ.

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Supply Current Section

TERMPWR Supply Current All Termination Lines = Open 1 2 mA

All Termination Lines = 0.2V 420 440 mA

Power Down Mode DISCNCT = TRMPWR 50 100

Output Section (Termination Lines)

Termination Impedance See Figure 1 104.5 110 115.5
Output High Voltage V
Max Output Current V

TRMPWR
LINE

V

LINE

V

LINE

= 4V (Note 1) 2.6 2.8 3 V
= 0.2V, TJ= 25°C –22.1 –23.3 –24 mA
= 0.2V –20.7 –23.3 –24 mA
= 0.2V, TERMPWR = 4V, TJ= 25°C

–21 –23.3 –24 mA

(Note 1)

= 0.2V, TRMPWR = 4V (Note 1) –20 –23 –24 mA

V

LINE

V

= 0.5V –22.4 mA

LINE

Output Leakage DISCNCT = 2.4V, TRMPWR = 0V to 5.25V,

REG = 0.2V, V

LINE

= 5.25V

10 400 nA

Output Capacitance DISCNCT = 2.4V (Note 2) 2 3.5 pF

Regulator Section

Regulator Output Voltage 2.6 2.8 3 V
Drop Out Voltage All Termination Lines = 0.2V 0.4 0.8 V
Short Circuit Current V
Sinking Current Capability V

= 0V –475 –650 –950 mA

REG

= 3.5V 200 400 800 mA

REG

Thermal Shutdown 170 °C
Thermal Shutdown Hysteresis 10 °C

Disconnect Section

Disconnect Threshold 0.8 1.5 2 V
Input Current DISCNCT = 0V –10 –30

Note 1: Measuring each termination line while other 17 are low (0.2V).
Note 2: Guaranteed by design. Not 100% tested in production.

µA

Ω

µA

Procedure:

1) Measure V

2) Set V

= 0.2V

L

3) Measure I

4) Impedance =

N.L.

REG

at 0.2V

MAX

VNL V

REG

...02

I

MAX

Figure 1. Termline Impedance Measurement Circuit

UDG-96102-1

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