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Original question:

LM3481 based SEPIC convereter radiating the EMI

LM3481: LM3481 based SEPIC convereter interfere the GLAN speed

user743401
Prodigy 110 points
Part Number: LM3481

Hi,

LM3481,SEPIC,9-36V input,19V out.

MOS,TI recommend Si7386DP or RJK0305DPB.

We use vishay SQJA64EP, LM3481 part interfere GLAN, making the speed down to 10MB/s.

If we use vishay SQJ412EP, GLAN speed is OK, can be 100MB/s.

Please give me the reason and solution.

Thanks!

  • 0
    TI__Guru* 76785 points
    Hello user743401,

    Thank you for considering the LM3481. The interference is most probably caused by switching noises. The SQJA64EP is a much faster device than SQJ412EP, so the it will create high di/dt and dv/dt during switching, and hence the switching ringing. If you really want to use SQJA64EP, you should increase your gate resistor to slow down the switch transient, then the interference can be avoided.

    Good luck.

    Thanks,
    Youhao Xi