SiP5668

Vishay Siliconix

New Product

www.vishay.com

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Document Number: 73099

S-41843—Rev. A, 11-Oct-04

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