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navgh77's avatar
navgh77
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1 month ago

Stratix 10 FPGA Dev Kit VCCIO_FMC voltage issue

The FMC VCC IO voltage level is adjustable using a resistor on the board as shown below. The default is 1.8V and that works fine. When I depopulate the resistor (R468) to get 1.2V, the output voltage...
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Fpga Devkit
AqidAyman_Altera's avatar
AqidAyman_Altera
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1 month ago

Hi,

 

Thank you for reaching out to us. I will help you with this.

Can you confirm what the devkit OPN is for this case?

AqidAyman_Altera's avatar
AqidAyman_Altera
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1 month ago

As per my understanding, even the devkit supports adjustable voltage at VCCIO_FMCA, if you only depopulate R468 to “get 1.2 V,” the regulator’s selection network is left in an invalid state. The kit’s power sequencing/monitor circuitry then detects an under‑voltage/fault and pulls the converter enable (EN) low, so the rail collapses to 0 V. Can you try to follow the resistor settings in the user guide, which leave all of the resistors open to get 1.2V.

Refer here:

https://docs.altera.com/r/docs/683674/current/stratix-10-gx-fpga-development-kit-user-guide/default-switch-and-jumper-settings 

  • AqidAyman_Altera's avatar
    AqidAyman_Altera
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    1 month ago

    Are you removing all the mentioned resistors, which are R460, R464 and R468? Based on my understanding, you depopulate R468 only.

    Correct me if I'm wrong.

     

    If you already done that, I suggest you below steps:

    1. Ensure R468 is removed and that R460 and R464 are not populated (verify no solder bridges). That yields 1.2 V per the user guide.
    2. Bring-up check
      • Power cycle the kit after changes.
      • Verify VADJ at the FMC test point and confirm the Power Good signal remains asserted.
      • Test without an FMC card first; then use only FMC cards that support 1.2 V VADJ.
    • navgh77's avatar
      navgh77
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      1 month ago

      All 3 resistors R460, R464 and R468 are de-populated, with no FMC card connected, VADJ output is still 0V and the enable signal for that DC-DC converter is low. 

    • navgh77's avatar
      navgh77
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      1 month ago

      AqidAyman_Altera​

      Any update on this issue? I believe the issue is LTM2987CY undervoltage level threshold is set above 1.2V for U70 supply I believe. We need to figure out how to program that chip to fix that. if we remove R446 and put a 10k for R443 (manually enabling U70), we will get the 1.2V output but EN_S10_VCCIO_FMCA will remain low and that is what enables the "12V" signal. This "12V" is used for the fan, J28 connector, and on the FMC connector so we will need this 12V, therefore we need EN_S10_VCCIO_FMCA to go high and be able to turn U70 on.

       

      Do you know how LTM2987CY (U31) is programmed? Do you have any documentation on it?

       

      Thanks,

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

        I understand your concern, but unfortunately, I don't think we have the method to program LTM2987CY documented. How about other voltages? Did you manage to get the voltage other than 1.8V?

    • navgh77's avatar
      navgh77
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      1 month ago

      I have another question since we still cannot figure out how to get 1.2V at the U70 output. 

      Can we change R434 and R439 to 30.2k ohm resistors to get 1.8V at the 2 outputs of U69? I just want to make sure this will not cause any issues. 

      Also, by doing this, can we ensure banks 4C, 4D, and 4E will run run on 1.8V as S10_VCCT_GXB and S10_VCCR_GXB are the IO supply for those banks?

       

      • AqidAyman_Altera's avatar
        AqidAyman_Altera
        Icon for Regular Contributor rankRegular Contributor
        22 days ago

        I checked LTM4650 datasheet, the typical Voltage at VFB Pins is 0.6V.

        I am not sure if it can get 1.8V at that pin.