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SN6505B-Q1: SN6505B-Q1 internal MOSFET Coss

Wei-Hao Chen (TW-FAE)
Expert 3260 points
Part Number: SN6505B-Q1

Hi Expert,

Could you please check with design team what is the Coss for SN6505B-Q1 internal MOSFET?

My customer needs to validate the voltage spike caused by the resonance between leakage inductance and internal MOSFET Coss to ensure they have enough design margin for the safe operation.

Thanks a lot

Best Regards,

Wei-Hao

  • 0
    TI__Guru 52640 points

    Hi Wei-Hao,

    Thanks for reaching out, I understand the reason why customer is requesting for Coss value. Please allow us until Tuesday to check if we can find an answer to this question easily, thanks.

    Regards,
    Koteshwar Rao

  • 0
    TI__Genius 17100 points

    Hi Wei-Hao,

    Thank you for posting to E2E! Capacitance contributing to resonance with transformer leakage inductance is a combination of pin capacitance, trace capacitance, and transformer capacitance. For this reason, the voltage spike -- and resulting emissions -- are unique to component selection and PCB routing, and Coss is not specified. The accurate method of extracting this spike's maximum value is through measurement.

    Voltage spikes caused by resonance are not expected to be problematic for SN650x devices or the transformers they are used with since there is sufficient design margin in the D1/D2 pin characterization for typical cases of SN6505 operation.

    Please let us know how much margin our customer requires for safe operation and which voltage levels they are expecting for the spikes in their system.


    Thank you,
    Manuel Chavez

  • 0 in reply to Manuel Chavez
    TI__Genius 17100 points

    Hi Wei-Hao,

    Hopefully your week is off to a great start. Our design team confirmed C_oss has a value of ~109pF. Please let us know if this is helpful for our customer or if there are any additional questions.


    Respectfully,
    Manuel Chavez

  • 0 in reply to Manuel Chavez
    TI__Expert 3260 points

    Hi Kote and Manuel,

    Thanks for checking the spec with design team for us, really appreciated your support

    Best Regards,

    Wei-Hao