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TPS54140 switching noise

Antony Pierre Carvajales
Intellectual 1910 points
Other Parts Discussed in Thread: TPS54140

Hi Team

Please assist my customer Attlia on the following design inquery

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I get too much noise on my DC DC regulator design TPS54140. 400mV switching noise, but what is most interesting is that the noisy switching frequency is twice the set frequency 1.9MHz is the set and 3.9MHz is the noise.  I tried adding ceramic caps to the output and it did not help.

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Please advise and comment how to improve this noise interference.

Thanks and regards,

Antony

  • 0
    TI__Guru**** 191445 points

    If switching noise is a concern, the first step is to check your measurement technique.  You should measure directly across the output capacitor(s) using a short (<1cm) ground lead.  Better still use the "tip and ring" method.  If you still find you have too much switching noise, check the layout.  Make sure the input bypass capacitor is directly connected to VIN and GND pins using short, wide traces or copper fill areas.  Make sure the circulating current paths are short.  Make sure the PH node trace is short and wide.  If all those criteria are met you may want to include an RC snubber from PH to GND and possibly extra filtering at the frequencies of interest.