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TPS54340B-Q1: Regarding snubber values in TPS54340B-Q1 design.

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Replies: 6

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Part Number: TPS54340B-Q1

Hi TI support,

Due to EMI concerns we are trying to add Rsnub=3.0E & Csnub=1100pF in TPS54340B-Q1 based design as shown in attached schematic. Place of their addition is highlighted with red line. Design details are VIN=10 to 20V, Vout=4.5V/ 2.5A, Freq=917KHz.

However, due to additions of above mentioned snubber, rise & fall time increase to 5.8ns & 20.11ns respectively which before were 2.4ns & 8.05ns respectively. Do you think these values are OK to be added or you suggest any modifications in that.

Regards,

jagdish

  • Jagdish,

    Snubber design depends on your application and your specifications. You can add any snubber you want as long as it fits your specs. Things to consider:

    1. Rsnub will be burning around 200mW worst case. Make sure it will not overheat.
    2. Efficiency will drop with the snubber. Measure efficiency of the system. Make sure this is acceptable.
    3. Consider improving the layout. Most EMI issues can be drastically improved with an optimized layout.

    -Sam

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    Product search: TI's Buck Converters, Controllers, and Modules.

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  • In reply to Samuel Jaffe:

    Hi Sam,

    Thanks for your comments. We will pay attention to points you mentioned.

    However, my concern for using snubber was more towards of interfering with internal timings of TPS54340B-Q1 after its rise & fall time have increased. Can it increase internal heating of IC? Or any other effects due to use of snubber (other than efficiency)?

    I will appreciate your answers to above queries.

    Regards,
    jagdish
  • In reply to Jagdish:

    Jagdish,

    The timings should be fine as long as the values are within reason. I don't foresee any notable extra heating, again within reason.

    -Sam

    ---------------------------- Resources ----------------------------

    Product search: TI's Buck Converters, Controllers, and Modules.

    Support: Tech Docs, Articles, Design ToolsE2E

  • In reply to Samuel Jaffe:

    Hi Sam,

    "The timings should be fine as long as the values are within reason".
    In context to your above statement please note that I have already mentioned values of both R & C along with their timings, do you still see any issues here particularly with R & C?
    Rsnub=3.0E & Csnub=1100pF

    Regards,
    jagdish
  • In reply to Jagdish:

    Jagdish,

    Those values should be fine.

    -Sam

    ---------------------------- Resources ----------------------------

    Product search: TI's Buck Converters, Controllers, and Modules.

    Support: Tech Docs, Articles, Design ToolsE2E

  • In reply to Samuel Jaffe:

    Thank you Sam for your support till now. I will try out these values & let you know further.

    Regards,
    jagdish

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