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TPS65185: reduce magnetic noise

VDM
Intellectual 325 points
Part Number: TPS65185

Hi,

I'm using the TPS65185 on my board.
This board is from my own design, and the magnetic noise is too high.

I quickly compared to a KOBO board, which also have a TPS65185, and the magnetic noise is significantly lower than on my own board.

Questions are :

1. Is there any adjustment that can be done on TPS65185 registers that can reduce the magnetic noise ?
2. It seems the noise mostly comes from the inductors. I used the recommended NR4012T2R2M and LQH44PN4R7MP0, which are said "shielded". Kobo's coils seems smaller, may they be the most significant source of noise reduction ?

Thanks for help !

Best regards,
Vincent.

  • 0
    TI__Genius 10885 points

    Hi Vincent,

    The registers may be used to disable and enable individual regulators to help diagnose the aggressors, but there are no features for reducing the noise while operating.

    Magnetic noise is most likely affected by the layout, particularly the area of the current loops for the regulators. It is the full return path of the current that will vary the most between hardware designs. Reducing the size of these loops is the best way to reduce magnetic noise, and placing bypass capacitors close to the pins can provide shorter return paths for high frequency switching currents. Reducing distances between ground pads for a regulator's input and output capacitors will also help reduce this total inductance and alleviate switching noise.

    Best Regards,

    Rick S.

     

  • 0 in reply to Richard Solarski
    Intellectual 325 points

    Hi,

    Thank you for your answer.

    Should the TPS65185EVM board be considered as a low noise design ?

    Best regards,
    Vincent.

  • 0 in reply to VDM
    TI__Genius 10885 points

    The EVM is not an EMC optimized design and is more for functional evaluation of the device and the internal registers. For instance, the EVM omits capacitors on the VEE_D and VDDH_D rails, which are highly recommended components for production designs.

    Best Regards,

    Rick S.