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Does LMH14203H maintain its EMI certification when operated in inverting mode (Vin = positive and Vout = negative)?

Ed Phaneuf
Prodigy 60 points
Other Parts Discussed in Thread: LMZ14203H, LMZ34002

Assuming I follow the rules in the datasheet, the LMZ14203H is EMI certified for radiated emissions without external filters and is EMI certified for conducted emissions with an external LC filter when operated in "normal" mode with Vin = positive and Vout = positive.  However, I want to use the LMZ14203H in inverting mode with Vin = positive and Vout = negative.

Based on the internal topology of the IC, what EMI changes, if any,  can be expected from using inverting mode.

Also, does anyone have experience with their product passing EN 55022 Limit (Class B) while using an LMZ power module in inverrting mode.

Thank you

Ed

  • 0
    TI__Genius 16025 points
    Hi Ed,

    Happy to help.
    EMI is dependent on every single parameter on the board. PCB layout, Bill of Materials used, topology and power needs.
    EMI performance will be completely different since the current loops between a buck and an inverting buck boost are different.
    Moreover, due to the change in layout and bill of materials the EMI ensured in the non inverting buck only mode doesn't apply any longer.

    That said, with a good layout (all high current component loops kept small and the use of a 4 layer board with a ground plane) and the use of shielded components, I see no reason to worry that EMI will deviate by much. It could be that you might even see an improvement but nevertheless you will need to test your final solution. The inductor used in the LMZ14203H is shielded.

    The LMZ34002 is an inverting LMZ module that passes the Class B rating.

    Let me know how I can be of further assistance.
    Thanks,
    Anston