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FPGA board to board connection with DS15BA101 and DS15EA101

Martin15
Prodigy 90 points
Other Parts Discussed in Thread: DS15EA101, DS15BA101, DS25BR110, DS25BR120

Dear Sir,

I have a prototyp board with an FPGA two DS15BA101 and two DS15EA101.

My target is to send data out of the FPGA (LVDS 2,5V) to the DS15BA101. From there AC coupled (1uF) over a Ethernet cable back to the AC coupled (1uF) DS15EA101.

When I send a endless data stream (200MBit/s) with the bit-sequence "0101010101", I also get "0101010101". That's fine.

But If I send "0110010101" I receive "0111010101". And the wrong "1" is also stable. I don't know why that happens.

Hope you have some ideas.

Are there some rules to follow when sending a data stream?

Thanks,

Martin

  • 0
    TI__Mastermind 43795 points

    Martin,

    It is possible that the DS15EA101 output common mode voltage is above the acceptable range for 2.5V FPGA LVDS.  The output common mode of the DS15EA101 is ~ 2.9V or VDD-375mV.

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Prodigy 90 points

    Hello Lee,


    thanks for the reply. Do you know another solution for a 2.5V LVDS maybe instead of the DS15EA101?

    Thanks,

    Martin

  • 0 in reply to Martin15
    TI__Mastermind 43795 points

    I would recommend using a DS25BR110 device to replace the DS15EA101.  It is not the same pinout, but it will output true LVDS output signals with a 1.2V common mode.

    It also has several levels of EQ which would be useful for longer cable lengths.

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Prodigy 90 points

    Hello Lee,


    thank you for the hint. I think I will try the DS25B110 and DS25B120 instead of the DS15BA101 and DS15EA101. I tried to order some samples but it seems that it is currently not possible... :-(

    Thanks,

    Martin

  • 0 in reply to Martin15
    Prodigy 90 points

    Hello Lee,

    one more question. I can't find a document like the http://www.ti.com/lit/an/snla112e/snla112e.pdf for DS15BA101 and DS15EA101 with the max. cable length for a CAT5 cable. Can you give me that information for the DS25BR110 / DS25BR120 solution?

    Thanks,

    Martin

  • 0 in reply to Martin15
    TI__Mastermind 43795 points

    Hi Martin,

    The maximum distance will depend on the datarate used.  Here is some typical data using the DS25BR120 as a driver and the DS25BR110 as a receiver.


                                                              Max Data Rate [Gbps]                          Recommended Settings

    Cable Length [m]                    w/o Sig. Con.           w/ Sig. Con.
    0                                                      3.25                           3.25                            PE00&EQ00
    5                                                      2.25                           3.25                            EQ01
    10                                                    1.50                           2.75                            PE01&EQ01, PE11&EQ00, PE10&EQ01, EQ10
    15                                                    1.00                           2.50                            PE11&EQ01, PE11&EQ00, PE10&EQ01
    20                                                    0.75                           2.25                            PE10&EQ01, PE11&EQ01
    25                                                    0.50                           2.00                            PE10&EQ10
    30                                                    0.25                           1.75                            PE11&EQ10

    PE settings on the BR120

    EQ settings on the BR110