sip5678 Vishay, sip5678 Datasheet - Page 10

• Manufacturer Part Number: sip5678
• Description: 15-line Scsi Bus Terminators
• Manufacturer: Vishay

SiP5678
Vishay Siliconix
DETAILED OPERATION
The SiP5678 is a multimode active terminator IC, which
detects the operating mode of the SCSI bus, and switches to
the appropriate termination configuration accordingly.
Two SiP5678 terminators are required at each end of a wide
SCSI bus to terminate 27 lines (18 data, 9 control). In LVD
mode the SiP5678 provides 105-W differential impedance and
112-mV differential bias between each TN/TP pair of
terminator lines. In S/E mode the SiP5678 provides 108-W
impedance and 2.7-V pull-up on each TxN pin, and low
impedance to ground on each TxP pin. In HPD mode the
SiP5678 disconnects from the bus and presents high
impedance to all TN/TP lines.
Each SiP5678 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
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Package Reliability represent a composite of all qualified locations.
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is an integrated 200-ms glich filter on the MODE input for
reliable operation in a noisy environments.
On power up, the SiP5678 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 SiP5678 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
SiP5678 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.
The DISABLE pin is used to connect/disconnect the SiP5678.
If it is pulled to GROUND the SiP5678 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.
DIFFSENS regulator is disabled.
The SiP5678 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.
In disconnect mode the
S-41843—Rev. A, 11-Oct-04
Document Number: 73100