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UCC28881: Spike on the Vin and Vo

Kuan Wei Chen (Kevin Chen)
Genius 9710 points
Part Number: UCC28881

Dear Team,

Here is Kevin from Delta Taiwan.

Customer will find the spike on the Vin bulk cap and Vo if the IC is operating.

If we remove the IC the input bulk cap won't have this spike.

So the spike is related to this IC.

We already follow the Webench design.

Do you have ideas on how to mitigate it?

BR

Kevin

  • 0
    TI__Guru 66135 points

    Hello Kevin,

    This does look like high frequency noise at the input if I were to guess.  To remove this you could split the input bulk capacitor into 2 and put an inductor in the middle to form a Pi filter.

    The other way to get rid of high frequency noise spikes is to reduce the size of the ESR.  You can also add high frequency bypass capacitors in parallel with the bulk capacitor with lower ESR to reduce ESR noise.

    Layout can also contribute to noise.  It is roughly 10 nH of inductance per 25.4 mm.  They could reduce this by making the traces as short as possible.

    There are tips in the data sheet on layout as well as a layout example that you could follow.

    One last thing is the noise real?  Did they take measurements at the input and output by using tip and barrel measurements? 

    Regards,

    Mike