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LM3481-FLYBACKEVM: question on feedback net

Part Number: LM3481-FLYBACKEVM
Other Parts Discussed in Thread: LM3481

Hi Team,

Could you help to comments why we add D4 D5 on feedback net of LM3481?

Thanks.

Regards, Sunny

  • Hello Sunny,

    Thanks for reaching out. When the FB pin of the LM3481 is grounded there is no soft-start functionality. For a flyback design this can be implemented on the secondary side by soft-starting the voltage reference and this is what you circled on the schematic of the EVM. The C and the R are defining the time constant of this soft start. 

    Kind regards,

    Elisabetta 

  • Hi Elisabetta,

    Really thanks for your comments.

    Regards, Sunny