73007 Datasheet, PDF (10/10 Pages) Vishay Siliconix – 9-Line SCSI Bus Terminators

SiP5630
Vishay Siliconix
New Product
DETAILED OPERATION
The SiP5630 is a multimode active terminator IC, which
detects the operating mode of the SCSI bus, and switches to
the appropriate termination configuration accordingly.
Three SiP5630 terminators are required at each end of a wide
SCSI bus to terminate 27 lines (18 data, 9 control). In LVD
mode the SiP5630 provides 105-W differential impedance and
112-mV differential bias between each T−/T+ pair of terminator
lines. In S/E mode the SiP5630 provides 108W- impedance
and 2.7-V pull-up on each T− pin, and low impedance to
ground on each T+ pin. In HPD mode the SiP5630
disconnects from the bus and presents high impedance to all
T−/T+ lines.
Each SiP5630 IC has a 1.3-V DIFFSENS Regulator output that
can be used to drive the DIFFSENS line of a SCSI bus. Since
only one DIFFSENS regulator is required at each end of the
SCSI bus each SiP5630 includes a MASTER/SLAVE pin to
enable or disable its DIFFSENS regulator. The DIFFSENS
regulator attempts to drive the DIFFSENS control signal to
1.3 V, but is current limited so that S/E or HPD devices on the
SCSI bus can override the DIFFSENS regulator and put the
bus into S/E or HPD mode of operation.
The MODE pin senses the operational state of the SCSI bus
by detecting the voltage on the DIFFSENS control line through
an external R/C low pass filter. 50 kW/4.7 mF are
recommended component values for the filter to meet SPI-3
mode change requirements.
Three status lines (S/E, LVD, and HPD) are provided by the
SiP5630. One and only one status line is asserted high when
its corresponding mode has been detected; the other two
status lines are driven low. The mode detection function
continues to work even when the SiP5630 is in disconnect
mode.
The DISABLE pin is used to connect/disconnect the SiP5630.
If it is pulled to GROUND the SiP5630 is in connect mode, and
operates as a terminator. If it is pulled to TERMPWR or left
open the device is in disconnect mode and presents high
impedance to the SCSI bus. In disconnect mode the
DIFFSENS regulator is disabled but the mode detection
circuitry continues to function and the status lines continue to
indicate which mode is detected.
The SiP5630 operates within SCSI specifications with the
TERMPWR voltage between 2.7 V and 5.25 V, which enables
it to operate in both 5-V and 3.3-V systems. The 2.7-V lower
limit guarantees correct performance in a 3.3-V system.
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Document Number: 73007
S-41263—Rev. A, 05-Ju1-04