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Ian_Maw's avatar
Ian_Maw
Icon for New Contributor rankNew Contributor
1 year ago
Solved

Does the PDN Tool Take DC Bias Loss Into Account?

Hi,

I worked in a company where someone did not account for loss of capacitance due to DC bias and the boards were unreliable for that reason.

I used the Cyclone V PDN tool to calculate the required values but I am not 100% certain whether or not the tool compensates for this factor.

Thanks.

Power
  • FvM's avatar
    FvM
    1 year ago
    Accepted. Let's say, PDN tool has no features to take account of capacitor voltage rating. Even if you know it, effective capacitance of different high Er capacitors at 0.5*Vrated ranges between 30 and 80 % of nominal capacitance.

5 Replies

  • FvM's avatar
    FvM
    Icon for Super Contributor rankSuper Contributor
    1 year ago

    Hi,
    PDN tool doesn't even use capacitor rated voltage, how should it consider C/V characteristic? Obviously, it's up to the designer to put in effective capacitance.

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

      Thanks, although your attitude is less than pleasant.

      • FvM's avatar
        FvM
        Icon for Super Contributor rankSuper Contributor
        1 year ago
        Accepted. Let's say, PDN tool has no features to take account of capacitor voltage rating. Even if you know it, effective capacitance of different high Er capacitors at 0.5*Vrated ranges between 30 and 80 % of nominal capacitance.
  • Farabi's avatar
    Farabi
    Icon for Regular Contributor rankRegular Contributor
    1 year ago

    Hello,


    When designing a power circuitry for your Cyclone V fpga, In the EPE you need to use Power Characteristics to "Maximum" instead of Typical. In PDN, please make sure the Zeffective is below the Ztarget.

    In PDN the dynamic current change can be set to >40% for VCC for defensive design to make sure the decoupling capacitors able to deliver enough power for FPGA during ramp up and user mode.


    regards,

    Farabi