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TPS43061: output ringing, reliability, causes, and alternatives

Lenio Cacula
Genius 16780 points
Part Number: TPS43061


This is a follow up to this forum post.

The TPS43061 exhibits a large ringing at the output. As discussed in the previous post, we have ways of mitigating that ringing, but without completely eliminating it. 

Questions:

1. Does the ringing affect the reliability of any parts in the circuit?

2. What is the main reason for the ringing? We seem observe a consistent 250MHz in multiple boards, including our EVM's and prototypes from the customer. If the frequency was a result of parasitics in the board, one would expect a range of different frequencies for multiple setups.

3. Would the ringing be different if we select different MOSFET's? If so, what would be the main parameter to consider? Total input capacitance?

Thank you!

  • 0
    TI__Guru* 78630 points

    Hi Lenio,

    Thank you for posting.  Answers to your questions:

    1. I don't think so if the voltage magnitudes are below the device rating.

    2. It is basically the resonance between the MOSFETs Coss and PCB trace inductances along the power current loops.  You are right that the exact frequency from board to board can vary slightly owing to parameter tolerances. 

    3. It is highly possible that the ringing will differ for different MOSFETs.  The main parameters include resonating parasitics.  The input capacitance would not matter much here.   It is the ac current loop parasitics.   For this boost circuit, the ac current loop is along the following path:  

    PGND --> Low side FET --> SW node --> High side FET --> Cout --> PGND. 

    Thanks,

    Youhao