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TLV62568: Switching Frequency

Allan Fan
Expert 7090 points
Part Number: TLV62568

Tool/software:

Hi expert,

Customer used TLV62568 and the use condition is 4Vin to 3.3Vout.  However, we found out the measured Fsw is always 25% lower compare to DS fig13, even if they used the same condition.

Would you please help clarify why it might happened like this?

Regards,

Allan

  • 0
    TI__Mastermind 22710 points

    Hello Allan,

    thanks for reaching out on E2E.

    The switching frequency depends on the output cap ESR and inductor DCR. Also the board layout can have an impact, when the traces add more ESR to the output filter path. Last but not least the inductor can also have a differing value due to tolerance, which impacts the switching frequency as well.

    Best regards,

    Andreas.

  • 0 in reply to Andreas Mueller
    TI__Expert 7090 points

    Hi Andreas,

    Customer measured the TLV62568EVM but also get the similar result. Do you have any idea?  

    Input: 4V , output: 3.3V , Iout: 500mA , FSW : 902KHZ

    Input: 4V , output: 3.3V , Iout: 1A , FSW : 782KHZ

    Regards,

    Allan

  • 0
    TI__Mastermind 22710 points

    Hello Allan,

    the switching frequency is usually difficult to reproduce exactly on different designs and I would not worry too much about the observed discrepancy.

    The datasheet results were measured with the DVB package version of the device and also on a special lab board which is slightly different than the EVM. This might be the reason for the observed difference.

    If the customer board results are similar to the EVM results, then this is actually a positive indication.

    Best regards,

    Andreas.

  • 0 in reply to Andreas Mueller
    Prodigy 10 points

    Hi Andreas,

    Thank you for your feedback, but we still don’t understand why the value we measured is so different from the value indicated in the specification (more than 25%). Can you please explain more?

    We understand that there will be a certain tolerance in switching frequency, but we would like to understand the reasons and principles of such a big difference.

    Conditions: Vin: 4V, Vout: 3.3V. Iout: 0.5A /1A
    What we know so far is:
    1. TLV62568EVM is similar to the Fsw we measured (0.5A/902KHZ, 1A/782KHZ)
    2. The output frequency curve corresponding to the specification is 1.25MHZ

    • Schematic

  • 0
    TI__Mastermind 22710 points

    Hello Walter,

    I will reach out to an expert and come back to you by end of today.

    Best regards,

    Andreas.

  • 0
    TI__Mastermind 22710 points

    Walter, Allan,

    it turned out the main reason for the observed difference in switching frequency is manufacturing process variation of the IC. This is normal on this device and no concern.

    Best regards,

    Andreas.