DS125BR800A: Two question for the DS125BR800A

Moving to high speed interface

For PCIe applications please Float the MODE pin.

That sounds like a lot of de-emphasis for PCIe application.  I would try to keep de-emphasis to 3.5 dB level.  What is the actual trace length and attenuation from the EP to the BR800A and from the BR800A to the CPU?

The 900mV level with -6 dB DE is not available with pins.  It would need to be programmed via EEPROM or SMBus slave mode.

To program 1000mV with -3.5dB DE you can use level 5 in the datasheet Table.

I would recommend to setup the BR800A to be configurable with SMBus Slave mode - any programming and tuning adjustments are simple and quick.

Regards,

Lee

The trace length from the EP to the BR800A and from the BR800A to the CPU are about 15 inches，PCB material is M4S，is that ok？

Is there any tool run in the OS to setup the BR800A with SMBUS？

Hi 

We have a GUI that can run on Windows 7.  Here is a link to the Sigcon Architect tool.

www.ti.com/.../sigconarchitect

This software tool requires a separate hardware connection to the SMBus to connect to the BR800A.

Regards,

Lee

M4S - Megtron 4 is a low loss material. I would not exceed the -3.5 dB setting. Also the input equalization setting should be on the lower side as well (either Level 1 or Level 2 in the datasheet).

Regards,
Lee

Hi Lee，

     But there are two couple board-to-board connectors between BR800A and CPU，and a couple board-to-board connector between BR800A and EP.

Most board to board connectors do not add a large amount of attenuation.  In the case of any high speed standards, they are a likely place to find unwanted or unintended coupling/noise between signals.

The EP and the CPU also must have some CTLE by PCIe specification.  The in-channel equalizers, like the DS125BR800A are only designed to help the RC and EP compensate for the total channel.

Regards,

Lee