TI UCC5618

UCC5618
18-Line SCSI Terminator
FEATURES
DESCRIPTION
• Complies with SCSI, SCSI-2, SCSI-3,
SPI and FAST-20 Standards
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.
• 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
BLOCK DIAGRAM
Patented Circuit Design
6/98
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.
This device is offered in low thermal resistance versions of the industry
standard 28 pin wide body SOIC, TSSOP and PLCC.
UDG-96005-1
UCC5618
ABSOLUTE MAXIMUM RATINGS
TEMPWR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V
Signal Line Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +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
PLCC-28 (Top View)
QP Package
TSSOP-28 (Top View)
PWP Package
* DWP package pins 12–18 serve as both heatsink and signal
ground.
* PWP package pin 23 serves as signal ground; pins 7, 8, 9,
20, 21, and 22 serve as heatsink ground.
DIL-24 (Top View)
N Package
SOIC-28 (Top View)
DWP 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.
2
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
Power Down Mode
All Termination Lines = Open
1
2
mA
All Termination Lines = 0.2V
DISCNCT = TRMPWR
420
440
mA
50
100
µA
110
115.5
Ω
Output Section (Termination Lines)
Termination Impedance
See Figure 1
104.5
Output High Voltage
VTRMPWR = 4V (Note 1)
2.6
2.8
3
V
Max Output Current
VLINE = 0.2V, TJ = 25°C
–22.1
–23.3
–24
mA
VLINE = 0.2V
–20.7
–23.3
–24
mA
VLINE = 0.2V, TERMPWR = 4V, TJ = 25°C
(Note 1)
–21
–23.3
–24
mA
VLINE = 0.2V, TRMPWR = 4V (Note 1)
–20
–23
–24
mA
–22.4
mA
Output Leakage
VLINE = 0.5V
DISCNCT = 2.4V, TRMPWR = 0V to 5.25V,
REG = 0.2V, VLINE = 5.25V
10
400
nA
Output Capacitance
DISCNCT = 2.4V (Note 2)
2
3.5
pF
2.6
2.8
3
V
Regulator Section
Regulator Output Voltage
Drop Out Voltage
All Termination Lines = 0.2V
0.4
0.8
V
Short Circuit Current
VREG = 0V
–475
–650
–950
mA
Sinking Current Capability
VREG = 3.5V
200
400
800
mA
Thermal Shutdown
170
°C
Thermal Shutdown Hysteresis
10
°C
Disconnect Section
Disconnect Threshold
0.8
Input Current
DISCNCT = 0V
1.5
2
V
–10
–30
µA
Note 1: Measuring each termination line while other 17 are low (0.2V).
Note 2: Guaranteed by design. Not 100% tested in production.
Procedure:
1) Measure VREG N.L.
2) Set VL = 0.2V
3) Measure IMAX at 0.2V
V
4) Impedance = REG
N. L.– 0.2V
I
MAX
UDG-96102-1
Figure 1. Termline Impedance Measurement Circuit
3
UCC5618
PIN DESCRIPTIONS
DISCNCT: Taking this pin high or leaving it open causes
the 18 channels to become high impedance and the chip
to go into low-power mode; a low state allows the
channels to provide normal termination.
LINE1–LINE18: 110Ω termination channels.
REG: Output of the internal 2.8V regulator.
TRMPWR: Power for the IC.
GND: Ground reference for the IC.
APPLICATION INFORMATION
UDG-96012-1
UNITRODE CORPORATION
7 CONTINENTAL BLVD. • MERRIMACK, NH 03054
TEL. (603) 424-2410 • FAX (603) 424-3460
4
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