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TPS53355: Ringing noise of TPS53353 and TPS53355

T Kishi
Genius 4425 points
Part Number: TPS53355
Other Parts Discussed in Thread: TPS53353

Hi

My Customer has question.

Customers are considering TPS53353 and TPS53355.

Measurement of the SW waveform with the EVM showed a difference in ringing noise, and Peak increased in TPS53353.

Is it correct with the recognition that the difference in the ringing noise is caused by the difference in the performance of the

internal FET because each device has almost the same layout and function?

Best Regard

T Kishi

  • 0
    TI__Prodigy 580 points
    Hi T Kishi,

    You are correct. The difference between TPS53353 and TPS53355 is the internal FETs to handle the the increased current limit. The EVMs are the same as well, except for the trip resistor values (which will not affect SW ringing).

    The difference in the internal FETs parasitic components can lead to different switch ringing. Please let me know if you have any questions on the ringing you are seeing. This app note also has some very useful information on SW ringing in Buck converters: slyt465.

    Thanks,
    Alec Heierman
    DC/DC Converters Applications Engineer
  • 0 in reply to Alec_Heierman
    Genius 4425 points

    Hi Alec

    Thank you for reply.

    I am about to change the snubber circuit constant to converge Ringing now.
    Waveforms that can be checked are as attached.

    TPS53353_Ringing.pdf

    There is something I want to check there.
    Since the maximum rating of the LL terminal of TPS 53353 is 27 V (20 ns), it does not exceed the maximum rating, but to what extent should it be reduced to take a margin?

    Regard

    T Kishi

  • 0 in reply to T Kishi
    TI__Prodigy 580 points

    Hi Kishi,

    You are seeing standard ringing for this part, and 24V gives you a comfortable margin. However, please be sure to check that 24V is max at your corner cases. 

    The ringing should be checked at the max Vin, max Vout, max Iout, and over the max and min values of the expected temp range the part will be operated at. In addition, the layout of the customer's board will most likely differ from the EVM, so you will almost certainly have to do some tuning and measurements to ensure the ringing is acceptable on the customer's board. 

    Reducing the ringing more can help ensure you stay under 27V at all use cases, so I will give you one more app note to reference for helping you tune the snubber. This app note is for this specific part, "slua831a". There is a nice table on page 10 that shows the different snubber values, as well as the boot resistor and boot cap values used.

    Thanks,

    Alec Heierman

    DC/DC Converters Applications Engineer