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DS125DF111: HOW TO SET MAXIM CTLE SETTING IN 1.25Gbps

Kevin cao
Prodigy 160 points
Part Number: DS125DF111

I use DS125DF111 as a retimer, which works at 1.25Gbps and 2.5Gbps. I need to set the CTLE in the front stage to the maximum setting. How do I set it specifically?

I setting below，is it correct?

addr    data    mask

0x31   0x00    0x60    //mode 0

0x2d   0x08    0x08

0x03   0x00    0xff

0x3a   0xff      0xff

0x1e   0x08    0x08

  • +1
    TI__Mastermind 36153 points

    Hi,

    In order to set the CTLE to maximum for a VCO divider of 4 or 8, this is correct.  Be sure to set the appropriate register selection prior to executing the settings you have described above.  In order to broadcast these settings to both channels, the data below can be sent.  Please see Table 8 in the datasheet for more details.

    addr    data    mask

    0xFF   0x0C   0x0F

    Please note that you will also need to alter the VCO settings since the default rate is not set for 1.25 or 2.5 Gbps.  Table 12 in the datasheet has examples for common data rates.  I believe the settings for 10.0Gbps would be most relevant for you.

    Thanks,

    Drew 

  • 0 in reply to Drew Miller1
    Prodigy 160 points

    Hi Drew,

     Thank you for your quick reply, I did set it this way, but I did not measure that the register 0x3a=0xff is the maximum magnification. At 1.25Gbps, it is not much different from 0x00. Does it need to be set elsewhere?

    Thanks,

    Kevin

  • 0 in reply to Kevin cao
    TI__Mastermind 36153 points

    Hi Kevin,

    Are you not seeing any impact when changing 0x3A from 0x00 to 0xFF?  Also keep in mind that CTLE boosts higher frequencies more than lower frequencies, so you would see much more boost with a 10.3125Gbps signal than a 1.25Gbps signal.

    Thanks,
    Drew

  • 0 in reply to Drew Miller1
    Prodigy 160 points

    Hi Drew,

    Thank you for your reply, but what I actually use is 1. 25GBP instead of 10.3125Gbps, the problem I have now is that the received signal can be detected but cannot be locked. I am a little worried that it is caused by insufficient  boost.

    Thanks,

    Kevin

  • +1 in reply to Kevin cao
    TI__Mastermind 36153 points

    Hi Kevin,

    Let's follow up on this topic on the other thread that is specific to lock issues.  I'll close this one for now.

    Thanks,

    Drew