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LMR43610-Q1: LMR43610-Q1: Using 5V version for 3.3V output + WEBENCH question

Chathura Fernando
Prodigy 10 points
Part Number: LMR43610-Q1

Tool/software:

I have a question about using the LMR43610-Q1 and the WEBENCH Power Designer.

My goal is to create a 3.3V/1A output, but the most available part for me is the LMR43610MSC5RPERQ1 (the 5V fixed version). I plan to use it in its adjustable mode. 

My question is about the WEBENCH tool's behavior: when I enter this specific ...MSC5... part number, it locks the output to 5V. Could you please explain why the tool does this? Can I safely ignore this software behavior, given the datasheet confirms the chip is adjustable?

As a potential workaround, I was wondering if this approach is valid:

  1. Generate a 3.3V design in WEBENCH for the LMR43610MSC3RPERQ1 (the 3.3V version).
  2. Take the recommended values for all the main power stage components (inductor, input/output capacitors, etc.).
  3. Use these exact components in my own schematic with the ...MSC5... IC,

  • 0
    TI__Expert 4395 points

    Hi,

    Yes, the approach is correct.

    1. Generate a 3.3V design in WEBENCH for the LMR43610MSC3RPERQ1 (the 3.3V version).
    2. Keep the passives same as the one obtained from WEBENCH.
    3. Change the feedback resistor to set the output voltage to 3.3V

    Below is the formula to get the value of FB resistors:

    Thanks,

    Pramanik Patel

  • 0 in reply to Pramanik Patel
    TI__Expert 4395 points

    Hi,

    I also have another suggestion:

    Use LMR43620MSC5 in WEBENCH and use the passives in LMR43610MSC5.

    But I would suggest to run a PSPICE simulation to verify the same.

    Thanks,

    Pramanik Patel