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TPS543C20: Power noise issue

Muhsiu Wei36
Intellectual 340 points
Part Number: TPS543C20

Hi Team,

I design an accelerated card that including 7-8 power rails. I find an issue at 1V output voltage as the shown figure below. As you can see the output voltage composed of high-frequency noise.

The frequency is around 520KHz which is another power rail switching frequency. This noise frequency is from  12V to 0.9V/80A step-down converter with 2 x TPS543C20.

1V noise frequency when 0V9 enable

I try to disable the 0.9V converter(TPS543C20) to see the noise frequency is exists or not. The result shows this noise frequency is indeed from TPS543C20.

1V0 output noise after disable the TPS543C20

Here is my PCB'A capture, the 1V converter is adjacent to the 0.9V converter. 

Could you please help to analyze the issue? thank you.

I also attached the schematic file below. 

TPS543C20RVFR.pdf

   

Muhsiu.

  • 0
    TI__Expert 5310 points

    Hi Muhsiu,

    The noise issue is not obvious based on the schematic. On this device, you may include a filter capacitor of at least 1nF to increase noise immunity across the RSP and RSN nets of the primary device. This may help with the noise seen when the other device is disabled.;

    As you mentioned, the noise you are seeing with the other device enabled appears at the switching frequency of another power converter in your design. In this case, it would help to examine the layout of the board and see if there may be a chance of inductive coupling across PCB traces. On the TPS543C20 device in a multi-phase configuration, it is important to shield the Vshare and Ishare traces in a design that may be susceptible to noise from other devices.

    Sincerely,

    Alec Biesterfeld

  • 0 in reply to Alec Biesterfeld
    Intellectual 340 points

    Hi Biesterfeld,

    Thanks for the reply. I would like to double-check with you is there have any issue since we did not separate GND to AGND and PGND? 

    Sincerely,

    Muhsiu.

  • 0 in reply to Muhsiu Wei36
    TI__Expert 5310 points

    It does help to separate PGND and AGND and then tie the grounds together at a single point to separate a "noisy" ground in PGND from a "quiet" ground in AGND. While this is not essential in all cases, it can surely help reduce the potential for noise related issues. I would also recommend evaluating the layout guidelines in section 11 of the datasheet to ensure all of the recommended design layouts are followed to the best extent possible.

  • 0
    TI__Genius 9540 points

    Hi ,

    Sorry that I will close this post first as there is no further concern . You can re-open it if you have any other question .

    thanks for understanding .

    BRs,

    Young