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TPS23756: noise test

Kaji@PAN
Mastermind 7795 points
Part Number: TPS23756

Hi,

I performed a noise test on the conduction emission test (communication port) on the board using TPS23756.
As a result, due to switching noise the standard is over 4dB.
I have taken various measures.
Among them, noise is reduced by deleting the capacitor C940 in the circuit diagram.
I think that the area around it is a noise source or noise path.
However, C940 can not be deleted due to the circuit configuration.
Is there any other effective countermeasure?

Best regards,

TPS23756 noise test.pptx

  • 0
    TI__Intellectual 1695 points

    Hi Kaji,

    From the schematic, the output PGND is connected to the DGND which provides a path for noise.

    Usually the C940 should be connected to the Earth ground. If there is no chassis, it can be connected to the PGND but the EMI will be worse.

    In this case you have to add common choke on the input side of PD controller or add RC snubber paralleled with switching FET to dump the spike.

    Thank you

    Best Regards

    Jack Chen