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Nicole04's avatar
Nicole04
Icon for Occasional Contributor rankOccasional Contributor
1 year ago

Agilex 5 HSIO Bank Clocks

Good day,

How can a 1.8V clock be connected to the HSIO banks? The Intel Agilex 5 Premium development kit seems to connect a few 1.8V LVDS clocks to HSIO banks powered at 1.1V or 1.2V (VCCIO_PIO). There is a voltage divider (orange block) added to the clock signals, but the resistors seem to be non-populated. However, the resistors are 10kOhm on both sides. Should one not use lower resistor values to not affect the impedance of the LVDS lines?

Should all HSIO pins within a bank not be within a tolerance of the VCCIO_PIO supply of that bank? None of these tolerances will allow for 1.8V LVDS.

Will it be better to add a resistor divider for all LVDS (1.8V) clock pairs to reduce them to 1.1/1.2V? Which resistor values are suggested to avoid losing signal integrity?

Kind regards,

Nicole

Board Debug

4 Replies

  • AqidAyman_Altera's avatar
    AqidAyman_Altera
    Icon for Regular Contributor rankRegular Contributor
    1 year ago

    Hello Nicole,


    From Si5332 clock gen datasheet, LVDS spec as below


    Vcm = 0.8V

    VPP_SE = 0.375V

    VPP_SE --> Signal swing at HIGH -> 0.8 + (0.375/2) = 0.9875V.


    That should be still within limit of HSIO pin.


  • Nicole04's avatar
    Nicole04
    Icon for Occasional Contributor rankOccasional Contributor
    1 year ago

    Hi Aqid,

    Thank you for your reply. I see what you mean. In the meantime, I set up these 1.8V clocks to be AC coupled and then biased to 1.1V or 1.2V depending on the HSIO bank voltage. Is this a better solution?

    Kind regards,

    Nicole

  • AqidAyman_Altera's avatar
    AqidAyman_Altera
    Icon for Regular Contributor rankRegular Contributor
    1 year ago

    Hello Nicole,


    I apologize as I can't verify the functionalities of your design if it is not following the same as the schematic of the development kit.


    If you can confirm the results will be within the limit for the pin, then should be okay.


    Regards,

    Aqid


  • AqidAyman_Altera's avatar
    AqidAyman_Altera
    Icon for Regular Contributor rankRegular Contributor
    1 year ago

    I hope the previous response was sufficient to help you proceed. As we do not receive any response from you on the previous question/reply/answer that we have provided. Please login to ‘https://supporttickets.intel.com/s/?language=en_US’, view details of the desire request, and post a feed/response within the next 15 days to allow me to continue to support you. After 15 days, this thread will be transitioned to community support. The community users will be able to help you on your follow-up questions.