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TPS546D24A: Design review

JH Shin
Guru 11400 points
Part Number: TPS546D24A
Other Parts Discussed in Thread: TPS546D24

Hello,

My customer requested TI's review of the TPS546D24ARVF design.

Please review their design below to see if there are any problems.

TPS546D24_N.pdf

Thank you.

JH

  • 0
    TI__Genius 11416 points

    Hi JH,

    Could you please complete the Excel spreadsheet (link below)? This will help us streamline the review process and allow us to provide a more thorough review. 

    https://www.ti.com/tool/download/SLURB01

    Thank you,

    Tomoya

  • 0 in reply to Tomoya Ide
    Guru 11400 points

    Hi Tomoya,

    Thanks for your help.

    Below is the Excel file you requested and the circuit diagram modified by the customer. Please review it.

    TPS546D24ARVF.zip

    They has additional questions.

    Q1. The customer's first circuit was created by referring to TI Webench. Why are the references, such as recommended settings, different for Webench and Excel file?

    Q2. Which reference should the user prioritize?

    Q3. When using the above design, is it possible to only monitor the status through PMBUS after normal operation without control through PMBUS?

    Regards,

    JH

  • 0 in reply to JH Shin
    TI__Genius 11416 points

    Hi JH,

    I found a few critical errors in the schematic.

    1. MSEL2 pin resistors: The customer has set it to 4-phase instead of 1-phase (stand-alone). Please change the bottom resistor (R1476) from 17.6k to 10k. 
    2. AVIN bypass capacitor is missing. Please add a bypass capacitor of minimum 1-uF X5R or better ceramic capacitor rated at least 1.5x the maximum AVIN voltage. Bypass to AGND. 
    3. Please make sure AGND and PGND are connected at a single point directly to the thermal pad. In the schematic, we usually separate AGND and PGND and connect them using a Net Tie, as shown below. Pin strap resistors (MSEL1, VSEL, ADRSEL, and MSEL2) should all be referenced to AGND. The AVIN bypass capacitor should also be referenced to AGND. 


      JH Shin said:
      Q1. The customer's first circuit was created by referring to TI Webench. Why are the references, such as recommended settings, different for Webench and Excel file?

      TI Webench is an excellent place to start. It provides additional information our Excel tool does not offer, such as efficiency, component part numbers, etc.

      However, when reviewing schematics, the Excel tool is better because it has a schematic and layout checklist, and you can quickly enter the values and check the result. I expect the difference between Webench and Excel to be small, but if there is a big difference, we need to look at it on a case-by-case basis.

      JH Shin said:
      Q2. Which reference should the user prioritize?

      Both tools are great, whichever customer feels comfortable with, but I recommend using Excel to review the final design. 

      JH Shin said:

      Q3. When using the above design, is it possible to only monitor the status through PMBUS after normal operation without control through PMBUS?

      Regards,

      Yes, the device should be able to power up without PMBus control, and the PMBus can just be used for status monitoring.