SIP5668 Datasheet, PDF (10/11 Pages) Vishay Siliconix – 14-Line SCSI Bus Terminators

SiP5668
Vishay Siliconix
New Product
DETAILED OPERATION
The SiP5668 is a multimode active terminator IC, which
detects the operating mode of the SCSI bus, and switches to
the appropriate termination configuration accordingly.
Two SiP5668 terminators are required at each end of a wide
SCSI bus to terminate 27 lines (18 data, 9 control). In LVD
mode the SiP5668 provides 105-Ω differential impedance and
112-mV differential bias between each TN/TP pair of
terminator lines. In S/E mode the SiP5668 provides 108-Ω
impedance and 2.7-V pull-up on each TxN pin, and low
impedance to ground on each TxP pin. In HPD mode the
SiP5668 disconnects from the bus and presents high
impedance to all TN/TP lines.
Each SiP5668 IC has a 1.3-V DIFFSENS regulator output that
can be used to drive the DIFFSENS line of a SCSI bus. 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. There
is an integrated 200-ms glitch filter on the MODE imput for
reliable operation in noisy environments.
On power up, the SiP5668 initially defaults to a high
impedance state on the termination pins. If the MODE pin
detects S/E or LVD level on the DIFFSENS signal of the SCSI
bus the SiP5668 will wait a standard delay (200 ms typical)
before changing its operating mode. During regular operation
if the MODE pin detects another bus mode change the
SiP5668 again waits a standard delay before changing its
operating mode. This mode change delay is implemented in
accordance with SCSI standards SPI-3 and higher.
Two status lines (S/E and LVD) are provided by the SiP5668.
One and only one status line is asserted HIGH when its
corresponding mode has been detected; the other status line
is driven low. Both status lines are driven low when HPD mode
is detected.
The DISABLE pin is used to connect/disconnect the SiP5668.
If it is pulled to GROUND the SiP5668 is in connect mode, and
operates as a terminator. If it is pulled to TRMPWR 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 SiP5668 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.
Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon Technology and
Package Reliability represent a composite of all qualified locations. For related documents such as package/tape drawings, part marking, and reliability data, see
http://www.vishay.com/ppg?73099.
www.vishay.com
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Document Number: 73099
S-41843—Rev. A, 11-Oct-04