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LM3406: Duty cycle

Pjs
Intellectual 870 points
Part Number: LM3406
Other Parts Discussed in Thread: TPS92641,

Hi, 

Why do the calculations in the LM3406 for buck duty cycle not include the efficiency estimate as they do with the TPS92641? They look like similar switching topologies, so I could use to understand why the calculations come out so different? 

Many thanks

  • +1
    TI__Mastermind 28655 points

    Hello,

    The datasheets were done at different times in different groups.  I tend to not use efficiency when designing circuits unless it's needed.  Most of the time it's fairly close and not that critical so I just take that into account knowing it will need a little margin.  Since most equations to design a buck converter are independent of the part choice you can design the buck power stage with either set of equations.  It's just where part specific values need to be used.  You can also just reduce the input voltage when doing calculations to compensate for efficiency as well.

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Intellectual 870 points

    Hi Irwin, 

    Thank you very much for your input on this. That's good to understand that it's just a different approach with each datasheet. I could use some guidance in my application - is there any chance we could continue this discussion offline at all?

    Many thanks

  • 0 in reply to Pjs
    TI__Mastermind 28655 points

    Hello,

    Sure, I'll send you an email and close this.

    Best Regards,