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WEBENCH® Tools: Web Bench Power Designer - "Fets could not be chosen"

Paul Bryson
Intellectual 490 points

Tool/software: WEBENCH® Design Tools

The "WebBench Power Designer" could not recommend FETs for my application. 

Why does it fail - voltage, current, thermal?

Is there a recommended method for getting around this?

Can I just parallel FETs to increase the output current?

  • 0
    Genius 4910 points

    Hi Paul,

    Could you please the device name and share the Webench design with us so that we can look into it.

    Regards,

    Atul

  • 0 in reply to Atul_Kulkarni
    Intellectual 490 points

    No specific device - no specific design. 

    I have been running many DC-DC scenarios for approx 250W - both buck and boost.   Unless the input voltage is very close to the output voltage, I get no complete designs from WebBench.

    And it always fails to find a real FET.

    My question is a general one.  What approach can I take when WebBench  provides no complete solutions?  

    For example: One approach I considered is to reduce the output current requirement until I get a complete design then put multiple of the recommended FETs in parallel and scale the other components to get my desired current. 

  • 0 in reply to Paul Bryson
    TI__Mastermind 25290 points

    Paul,

    WEBENCH has design checks related to thermal and timing considerations and also some specific checks related to the IC itself. In addition, there are thermal and power considerations when selecting components like FETs. So, it is possible that if you try out some stringent condition, the design fails in the tool or is unable to find a real FET. To find the actual cause, it would be great if you can share some design conditions and the device you are looking to design with.

    Like you said, one way would be to ease the requirements and see if you can create a design. Of course, there would now be a need to tweak or review the design that comes out from the tool in order to ensure it meets the actual stringent requirements. We can get further help on this from product experts to review such designs and recommend options. In addition, you can also explore the TI reference designs and see if you can find a reference design similar to your requirements.

    Please let me know if you have any further questions or need help.

    Regards,

    Amod