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PMP8878: C2

Kuramochi Tadahiko
Guru 28715 points
Part Number: PMP8878

Hi,

My customer is referring  PMP8878 and has questions about "C2" as below;

1. How should we design the rated current of C2?

2. How should we design the capacitance of C2?

3. How should we design the rated voltage of C2?

Best Regards,

Kuramochi

  • 0
    Guru 28715 points

    Experts,

    How is this situation?

    Best Regards,

    Kuramochi

  • 0 in reply to Kuramochi Tadahiko
    TI__Guru 55905 points

    Hi,

    It is actually designed by its impedance. Its impedance Zc2 1/(2pi fsw C2) needs to be much smaller than the voltage across the transformer, its peak current is the same as the peak current in transformer or the MOSFET, Its voltage rating is quite low in steady state operation. But to consider its in worst case when transformer in saturation is voltage rating can be in theory to be Vin. But when this really happens, the OCP should work. So typically its voltage rating can be designed to tolerate with your OCP current and use that current to Zc2, then add 2x for worst case of resonant.