Hi all.

I have a question about the pre-emphasis of LVDS TX.

If the data rate is about 2Gbps, is it needed to use the pre-emphasis?

How about using large current (more than 4mA) without pre-emphasis?

I searched some papers about the pre-emphasis but I could not find any good examples.

If you have some advice on the pre-emphasis, please let me know.

Thank you.

Hello:


"If the data rate is about 2Gbps, is it needed to use the pre-emphasis?"
 The decision of using equalizer or not lies on the channel conditions around the communication bandwidth. If the channel loss is much more great than 3dB or there is significant ISI, then the channel equalizer is necessary.    

"How about using large current (more than 4mA) without pre-emphasis?"

Big transmitter signal can also generate big ISI, so you still need equalizers if the channel isn't good enough.

"I searched some papers about the pre-emphasis but I could not find any good examples."
    paper:  
               W. J. Dally and J. Poulton, “Transmitter equalization for 4Gb/s. signaling,”
               JSSC and ISSCC, many,many......
    theory book:    
       W. J. Dally, J. W. Poulton, Digital Systems Engineering, Cambridge University Press, 1998.
      J. G. Proakis, Digital Communications, 4th Edition, McGraw-Hill, 2001.
"If you have some advice on the pre-emphasis, please let me know."
1:  careful measure or model you physical channel.
2: make you pre-emphasis programable.

In addition to the above -

The PCB trace needs to be a distibuted network with multiple RLC elements. Do not lump them all togther for the response will be different.

Data encoding for these devices can be in a run length limited (RLL)fashion (8B/10B is commonly used in these systems) or NRZ data (n run length limitations)

With the above, the patterns to test the system need to include a bunch of different possible patterns including isolated 1's in long strings of 0's and a number of other possible test cases.