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TPS40170: Using Faster FETs results in gate drive oscillations.

Part Number: TPS40170


my question is reguarding the Cin and Cout in my design,

i'm having a ringing problem and would like to implement an RC snubber circuit in my design , in order to prevent the ringing issue,

According to my design, what are the recommanded Capacitance at the input and output stage?

should i cut some caps at the output ? or add some at the input?, what do you think can cause the ringing issue (if you take a look at the desing).?DC2DC TI qus.docx

  • Victor,

    Ringing is not inherently bad with typical part selection. Bad ringing is often caused mostly by the layout.

    Ringing is due mostly to the parasitic capacitance of the FETs/inductor resonating with the parasitic inductance of the loop. A larger loop (from the layout) will create more inductance which will create more ringing. If redesigning the layout is an option, please share it and I'll give you my thoughts on optimizing this loop. If a new layout is not an option:

    A snubber will definitely help with this but it will be at the expense of efficiency. You can also increase Rboot (looks to be 2.2 ohms at the moment. Could try 10 ohms) or add gate resistors.


  • In reply to Samuel Jaffe:

    Hi Sam,

    Thanks for the quick reply,

    According to my design in which you have observed , what can be the recommanded snubber RC values?

    or what could be the efficient way to calc them?



  • In reply to victor saada:


    I usually start with 100pF and 10 ohms but this article goes into detail for optimization.