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TPS40305: Generating high noise and failing in the Certification

Part Number: TPS40305

Hi,

We are using TPS40305 to convert 8-16V (VIN) to 4.5V (@9A) Vout.

This power supply is becoming main culprit in the PTCRB certification  (not able to reach to the limitations for TIS). As soon as we remove this supply from equation the system gets through the process. Even we have already tried to put a shield on but no effect. At last we are planning to redo the layout as well add more filter circuit at the input and output both the terminals. 

Here is the design snippet:

I'm looking to add PI filter as well multiple low value capacitors in the input path, as follows for output.

Is it gonna help improve the performance? Anything specific that you thing we should take care during routing?

Thanks,

Dhvanish

  •  

    Is this follow up on this post - https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1018937/tps40305-emi-issue by  ?

    In that post, I asked whether this was radiated or conductor, and at what frequency the design is failing, so we know where to focus our efforts on EMI noise reduction.

    Pi filters on the input and output may help contain conducted EMI to the local converter, which can also help reduce radiated EMI by reducing the area of radiation exposed to the high-frequency noise, but there may be other, less invasive solutions to reduce the EMI such improving input and output bypassing, changing boot-strap and gate drive resistors to change the rise, fall, and parasitic ringing of the switching node, or changing the layout to improve the high-frequency bypassing impedance.

    Most likely, these later improvements to reduce the source of the noise, and remove them more locally to the converter would be more effective than Pi filters to contain them to a smaller area.

  • Peter,

    We are failing majorly in the TIS during PTCRB and failing to get the enough sensitivity in few of the bands. We tried by putting an external shield also on top of switcher - no change in the overall performance. 

    As soon as we remove the switcher (turn off the supply to switcher) and provide external clean DC supply - performance improves by huge number. So this leads us to doubt more on the connected noise.

    I would be more then happy to share the layout file with you and have it reviewed. Also, I can share the current statistic of TIS testing. I have sent a request to you with my email ID. I'll share it over there amid to the confidentiality of the design.

  • Hi Dhvanish,

    Since you may have contact Peter through email, I will close this thread first.

    Thanks,

    Lishuang