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TPS54290: PGND1 and PGND2 connection

Ella KIM
Expert 3952 points
Part Number: TPS54290

Hi,

My customer is looking for a two channel buck to supply C2000 MCU. It's 12-to-3.3V application. MCU has two grounds - AGND and DGND - which connect to each other thru a 0ohm resistor for noise minimization. I'm wondering if PGND1 pin #4 and PGND2 pin #13 can be connnected to different node. They want to connect PGND1 pin #4 to MCU's AGND and PGND2 pin # to MUC's DGND. Technically AGND and DGND has the same voltage level because of short tie or 0ohm connection but still they're separated in PCB.

Below is current customer schematic. What they want is to generate DVCC_3.3V and AVCC_3.3V separately.

Please advise. 

Sincerely,

Ella

  • +1
    TI__Mastermind 24000 points

    Ella,

    Yup, even though technically they should be at 0V, the quieter ground connects the noisier ground via a small trace to minimize the noise coupling. In this specific case, PGND pins will be noisier than the GND pin of TPS54290. Given that, it looks like their original schematic does have additional filtering so it may work out with PGND pin. But they should consider GND (pin 11) which is the analog ground pin of TPS54290 and should be quieter than PGND pins. 

    Thanks,
    Amod

  • 0 in reply to Amod Vaze
    TI__Expert 3952 points

    Hi Amod, 

    Thank you for prompt reply. To clarify my question, please find the figure below : 

    Instead of customer schematic, they're considering the structure like figure above. Do you think it would work? ANGD is quiter than DGND so I connect GND pin #11 with AGND. 

    What do you think?

    Ella

  • +1 in reply to Ella KIM
    TI__Mastermind 24000 points

    Yes AGND to GND (11) and DGNG to PGND1/2(4/13) should work.

    Thanks,

    Amod