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Jiayi_H_Intel's avatar
Jiayi_H_Intel
Icon for Occasional Contributor rankOccasional Contributor
5 years ago

Why LVDS output clock must be divided by division factor?

Hi experts,

I am using LVDS transmitter with internal PLL, on 10M50 board. Just find that tx_outclock must be divided by a division factor, which has some fixed value: 10, 2, 4, 20.

Why can't we just send the clock rate equal to data rate? what's the purpose to do the division?

3 Replies

  • YuanLi_S_Intel's avatar
    YuanLi_S_Intel
    Icon for Regular Contributor rankRegular Contributor

    Hi Jiayi,

    The division is actually the factor convertion from LVDS fast clock to tx_outclock. Fast clock is a high frequency that is converted from user supply clock and it is meant for the mechanism of LVDS.

    You will need to refer to the serialization factor that you choose for the setting of the division.

    For more information, please refer to our user guide for that:

    https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/ug/ug_altera_lvds.pdf (Page 18)

    Thank You

    • Jiayi_H_Intel's avatar
      Jiayi_H_Intel
      Icon for Occasional Contributor rankOccasional Contributor

      That means if I set data rate to 200Mbps, and serialization factor is 10. I can choose 10, 2, 4 or 20 for division factor in drop list. So the fastest output clock is 100M( division factor is 2), right?

  • YuanLi_S_Intel's avatar
    YuanLi_S_Intel
    Icon for Regular Contributor rankRegular Contributor

    Yes, you can said so. But for accurate output clock, it would be good if you could do model sim or measure it in hardware level.