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TPS40210: TPS40210 MOSFET grid ringing

w w2
Prodigy 90 points
Part Number: TPS40210

TPS40210, + 24V boost to + 36V, using ti.com simulation circuit, the ring will be generated at about half of the rising edge of the grid, the amplitude is about 5V, and the frequency is about 133MHz. Why? The MOSFET is csd18533, the grid resistance is 5.1 ohms, and the sampling resistance is 0.002 ohms. When the grid resistance is changed to 33 ohms, a 4.7nf capacitor in parallel will not ring, but the rising edge is very oblique, which will be bad for MOSFET. What is the cause of this? Will it affect radiation? How to solve it? Thank you!

  • 0
    TI__Mastermind 21720 points

    Hello w w2,

    Thanks for reaching out and using the TPS40210.

    Are you referring to the ringing on the switch node? The ringing of the switch node id due to parasitic components of the MOSFET and the switch node.I am assuming that the 33ohm and 4.7nF capacitance are a snubber  that was placed. This is recommended to help minimize the high frequency ringing and can be optimized using this application note. The snubber will help to minimize the ringing which helps to reduce EMI at higher frequencies.

    Let me know if you have any questions.

    -Garrett

  • 0 in reply to Garrett Roecker
    Prodigy 90 points

    Thank you very much for your professional answer.  What I want to ask is MOSFET gate ringing. Please reply again, thank you !