SiP5630

Vishay Siliconix

New Product

www.vishay.com

10

Document Number: 73007

S-41263—Rev. A, 05-Ju1-04

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.