UCC5641 Datasheet, PDF (1/4 Pages) Texas Instruments – Low Voltage Differential LVD SCSI 9 Line Terminator

UCC5641
Low Voltage Differential (LVD) SCSI 9 Line Terminator
FEATURES
• First LVD only Active Terminator
• Meets SCSI SPI-2 Ultra2 (Fast-40)
and Ultra3 / Ultra160 (Fast-80)
Standards
• 2.7V to 5.25V Operation
• Differential Failsafe Bias
• Reversed Disconnect Polarity
DESCRIPTION
The UCC5641 is an active terminator for Low Voltage Differential (LVD)
SCSI networks. This LVD only design allows the user to reach peak bus
performance while reducing system cost. The device is designed as an
active Y-terminator to improve the frequency response of the LVD Bus.
Designed with a 1.5pF channel capacitance, the UCC5641 allows for mini-
mal bus loading for a maximum number of peripherals. With the
UCC5641, the designer will be able to comply with the Fast-40 SPI-2 and
Fast-80 SPI-3 specifications. The UCC5641 also provides a much-needed
system migration path for ever improving SCSI system standards. This de-
vice is available in the 24 pin TSSOP and 28 pin TSSOP for ease of lay-
out use.
The UCC5641 is not designed for use in single ended or high voltage dif-
ferential systems.
BLOCK DIAGRAM
SOURCE ONLY FROM TRMPWR AND THE ENABLED TERMINATIONS
TRMPWR 28
2.7V to 5.25V
SOURCE 5–15mA
SINK 200µA MAXIMUM (NOISE LOAD)
REF 1.3V
1.3V ± 0.1V
OPEN CIRCUIT ON POWER OFF
OR OPEN CIRCUIT IN A
DISABLED TERMINATOR MODE
20k
0.1µF
DIFFB
11
LOW
FREQUENCY
FILTER
50Hz – 60Hz
2.4V > 1.9V
HIGH IMPEDANCE RECEIVER
EVEN WITH POWER OFF
0.7V > 0.5V
SOURCE/SINK REGULATOR
124
REF 1.25V
10µA
124
DISCNCT 15
GND
14
REG
1
56mV
–+
56mV
+–
56mV
–+
56mV
+–
HIGH POWER
DIFFERENTIAL
SINGLE
ENDED
52
52
52
52
4.7µF
12
DIFSENS
27 LVD*
4 L1–
3 L1+
26 L9–
25 L9+
* 28 pin package only
SLUS397 - JANUARY 2000
UDG-99160