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imuguruza's avatar
imuguruza
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1 year ago

Issue with Cyclone 10 LP PLL

Hi there,

I am working in a bring-up of a board that contains a Cyclone 10 LP FPGA.

I am trying to use the 2x PLLs that the FPGA contains.

I have generated from the 100MHz input clock, 2x 200KHz using ALTPLL IP.

But, I see that the "locked" out signal goes from "1" to "0" after programming the sof and that the output frequency us around 170KHz instead of the 200KHz.

I have tried different compesation modes and made tests with different frequencies, but I always get the same behavior, "locked" signal does not get stable in "1" and the PLL output frequency is always below the target (i.e. 15MHz I get 12MHz, 5MHz I get 4Mhz, ...)

I am unsure if it's IP config problem or something else, like HW isuse.

A small capture of the IP:

How can I proceed?

Thanks

Configuration

8 Replies

  • imuguruza's avatar
    imuguruza
    Icon for New Contributor rankNew Contributor
    1 year ago

    I can confirm that the input clokc is working fine, as I have used it to toggle LEDs using a counter module.

    I am wondering if it is mandatory to have an isolated analog reference plane in the PCB as stated in doc an958:

    In my design, we only have a ferrite to isolate VCC_PLL but we have not created an isolated GNDA, it is tied to digital ground.

    • FvM's avatar
      FvM
      Icon for Super Contributor rankSuper Contributor
      1 year ago
      Hope you have also bypass capacitors next to VCC_PLL and other supply pins.
      Power integrity is hardly a problem unless your PCB has many fast switching outputs.
  • imuguruza's avatar
    imuguruza
    Icon for New Contributor rankNew Contributor
    1 year ago

    Well, the board has VCC_PLL decoupling caps, but is also missing a ferrite bead for VCCA feeding voltage.

  • imuguruza's avatar
    imuguruza
    Icon for New Contributor rankNew Contributor
    1 year ago

    It looks to be a hw, the "GNDA" pins are missing GND connection

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

    Okay noted. Has the issue been resolved after you are connecting the GNDA pins to GND?

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

    I’m glad that your question has been addressed, I now transition this thread to community support. If you have a new question, Please login to ‘https://supporttickets.intel.com’, view details of the desire request, and post a feed/response within the next 15 days to allow me to continue to support you.