UCC5631A Datasheet, PDF (1/6 Pages) Texas Instruments – Multimode SCSI 9 Line Terminator

UCC5631A
Multimode SCSI 9 Line Terminator
FEATURES
• Auto Selection Single Ended (SE) or
Low Voltage Differential (LVD)
Termination
• Meets SCSI-1, SCSI-2, SCSI-3, SPI,
Ultra (Fast-20), Ultra2 (SPI-2 LVD)
and Ultra3 Standards
• 2.7V to 5.25V Operation
• Differential Failsafe Bias
• Thermal packaging for low junction
temperature and better MTBF
• Master/Slave Input
• Supports Active Negation
• 3pF Channel Capacitance
• Reversed Disconnect Polarity
BLOCK DIAGRAM
DESCRIPTION
The UCC5631A Multimode SCSI Terminator provides a smooth transition
into the next generation of the SCSI Parallel Interface (SPI-2). It automati-
cally senses the bus, via DIFFB, and switches the termination to either sin-
gle ended (SE) or low voltage differential (LVD) SCSI, dependent on which
type of devices are connected to the bus. The UCC5631A can not be used
on a HVD, EIA485, differential SCSI bus. If the UCC5631A detects a HVD
SCSI device, it switches to a high impedance state.
The Multimode terminator contains all functions required to terminate and
auto detect and switch modes for SPI-2 bus architectures. Single Ended
and Differential impedances and currents are trimmed for maximum effec-
tiveness. Fail Safe biasing is provided to insure signal integrity. Device/Bus
type detection circuitry is integrated into the terminator to provide automatic
switching of termination between single ended and LVD SCSI and a high
impedance for HVD SCSI. The multimode function provides all the perfor-
mance analog functions necessary to implement SPI-2 termination in a sin-
gle monolithic device.
The UCC5631A is offered in a 36 pin SSOP package, as well as a 48 pin
LQFP package for a temperature range of 0°C to 70°C.
DIFFB 21
MSTR/SLV ¹⁹
2.15V
HIPD LVD SE
35 34 33
0.6V
SE REF 2.7V
SOURCE/SINK REGULATOR
LVD REF 1.25V
10µA
DISCNCT 17
TRMPWR 36
ENABLE
SWITCHES
MODE
SE
ALL
SWITCHES
UP
LVD
DOWN
HIPD
OPEN
DISCNCT OPEN
HIPD
LVD
SE
(NOISE LOAD)
REF 1.3V
1.3V
20 DIFSENS
–15mA ≤ I_SOURCE ≤ –5mA
50µA ≤ I_SINK ≤ 200µA
110
124
56mV
–+
56mV
+–
52.5
52.5
SE GND SWITCH
110
5 L1–
4 L1+
124
56mV
–+
56mV
+–
52.5
52.5
SE GND SWITCH
32 L9–
31 L9+
18
GND
8 9 10 26 27 28
HS/GND
1
REG
Note: Indicated pinout is for 36 pin SSOP package.
SLUS443 - OCTOBER 1999
PATENTED CIRCUIT DESIGN
UDG-99165