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LMR62421 simulation in Webench

Josef Rypar
Prodigy 80 points
Other Parts Discussed in Thread: LMR62421

Hello,

I'm about to use the LMR62421 boost regulator for boosting from 3.0V-5.5V to 16V with max. 0.2A output current. When I try to simulate the design using Webench I get following message

When I click the green button "Show Why Parts Were Not Found" I get following screen saying that design is not stable and the calculator cannot create the design.

Does it mean that the Calculator has some limitations or the circuit cannot be made working? I've designed the converter with this chip "manually" using datasheet and I don't see any reason why it should not work.

Please help me understand the Webench behavior.


Best Regards,

Josef Rypar

  • 0
    TI__Genius 16025 points
    Josef,

    Apologies for the delayed response. We are looking into this now and I will let the modelling group know as well. I did a quick check on operating specs and see no issues to run this configuration. Let me know if you have any Bill of materials related questions.

    Thanks,
    Anston
  • 0
    TI__Genius 15810 points
    Hello Josef,
    As Anston mentioned, we do not see a big problem with the design. i will move your question to the Webench forum for them to take a look at.
    Regards,
    Akshay
  • 0
    TI__Intellectual 1825 points

    Hello Josef,

    I apologize for the issues you have encountered while using WEBENCH® Power Designer for your LMR62421 design.  As Akshay and Anston has previously mentioned, your design operating specs should not be an issue.  

    The reason why WEBENCH does not create a design for you is because the calculated Phase Margin for the recommended WEBENCH design is less than 35deg (the limit that we put on all WEBENCH designs for stability), although the calculated value for the LMR62421 design was not that far off.  

    I am currently working to update our design calculations for the LMR62421 so that the components selected for the design keep the Phase Margin for the design above the 35deg limit, and to prevent any other issues like this from occurring.  

    I hope this helps clarify the issue.  I will try to have a fix for this released within the next couple of days.  If you have any other questions or concerns, please let me know.

    Best Regards,
    Jonathan Arzadon
    Applications Engineer 
    WEBENCH Design Center
    Texas Instruments

  • 0 in reply to Jonathan Arzadon
    Prodigy 80 points

    Hello Jonathan and others,


    thank you for interest in this issue. Please let me know when the update is completed, I'd like to double check the circuit.

    Best Regards,

    Josef Rypar

  • 0 in reply to Josef Rypar
    TI__Intellectual 1825 points
    Hello Josef,

    The update has been released. You should now be able to create your LMR62421X design in WEBENCH® without any issue.
    Please let me know if you have any other questions or concerns.

    Best Regards,
    Jonathan Arzadon
    Applications Engineer
    WEBENCH® Design Center
    Texas Instruments