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LM3478

John Mitchell26
Prodigy 90 points
Other Parts Discussed in Thread: LM3478

I am trying to design a converter: 11-16V input, 12.7V output at 1.1A max output current.

Webench correctly identifies that I need a SEPIC and suggests the LM3478 as a control IC (which I had already thought would be a good one to use), and it appears to simulate OK with the default components. Wherever possible, I need to use our stocked components in my design, some of which are not in your library. But in the BoM screen it will not let me define a 'custom component'. The red 'Create a Custom Part' button is simply not there.

I have checked Webench with a couple of other controllers (selected at random) and for them the red button IS there, but for the LM3478 it simply isn't there !

Is there some reason why, or am I doing something wrong ? Is there a fix or a workaround ?

  • 0
    TI__Mastermind 41310 points

    John,

    I have verified that the custom button seems to be missing in this case. I will have the issue investigated. Thanks for bringing this to our attention.

  • 0
    TI__Mastermind 41310 points

    John,

    I found out that the Custom Component feature has been taken from the SEPIC designs that are generated in WEBENCH®. You are not doing anything wrong. Apparently, we had some issues with SEPIC designs using custom components and the feature was removed. We have to be sure that the design is robust and accurate that is produced.

    If you are not updating the value of the component being used, you can add notes to the design that state the "stocked" component you will be using as a replacement. If you are changing the component value slightly, we still allow the editing of the bounds on the component values. Simply edit the upper and lower bounds and find a suitable value (the same as the stocked part) and use it with the note added.

    Adding notes:

    Updating limits for components:

    This might help you with your issue of using the stocked components with your design.

  • 0 in reply to Britt Brooks - Online Design Tools
    Prodigy 90 points
    Thank you for clarifying that. Would you be able to put a note in Webench to explain that (e.g. a comment "not available for SEPIC designs" where the 'Custom Component' button used to be) and/or something in the 'help' to avoid other people getting confused ?