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Original question:

LM51581-Q1: Proper simulation tool?

LM51581-Q1: Boost snubber circuit

Steven Balick
Prodigy 90 points
Part Number: LM51581-Q1


Tool/software:

I would like to have a design provision for a snubber circuit on the switching node. To especially determine the power rating and size of components, one key factor is the switch output capacitance.  This is not listed in the datasheet. Prior to putting my design through PSPICE (I do not have it installed yet), I'd like to at least work through Excel to determine reasonable estimates for placeholders. Once the design is in place, the supply will be instrumented and final values determined.

Can you provide a typical value, and the range across temperature of the internal FET Coss?

Thank you.

Steven

  • 0
    TI__Mastermind 18655 points

    Hi Steven,

    thank you for using E2E.

    Unfortunately we do not specify a value for Coss of the internal MOSFET.

    As the right values for the snubber are nevertheless very depending on parasitics on the final PCB, i would recommend to have placeholders in the design (0805 for the resistor, 0603 for the capacitor) and adjust the snubber when the design is built. 

    https://www.ti.com/document-viewer/lit/html/SSZTBC7 I can recommend this article on how to calculate the RC snubber in 7 steps.

    If you have further questions please feel free to ask.

    Best regards,

    Moritz