Forum Discussion
New ContributorDoes 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.
- 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
FvMSuper Contributor
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_MawThanks, although your attitude is less than pleasant.
- FvMAccepted. 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.
- Ian_Maw
Thank you very much.
Farabi_AlteraRegular Contributor
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
