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WEBENCH® Tools/TPS54228: TPS54228 CURRENT LIMIT?

or nsl
Intellectual 280 points
Part Number: TPS54228
Other Parts Discussed in Thread: TPS62140A,

Tool/software: WEBENCH® Design Tools

Hi,

Webench used to design with 54228 as buck 2v to 5v with max current limit of 1.5A. While testing the circuit with load, the load reached (@5v+-) even more than 2.7A until it made the cut off. as it noted on the data sheet that it should limit the current cycle by cycle, please advice if 54228 can limit the current to 1.5A and is the webench back this design? and if so, which component we need to replace instead as in the attached webench simulation so we can get max 1.5A - meaning to stay there at max 1.5A even the load is higher? 

Thanks

  

  • 0
    TI__Guru*** 146030 points
    I think you mean that you told Webench to make a 1.5A design? i.e. 1.5A was the output current that you entered?

    No power supply will limit to some precise value without any tolerance. As well, very few power supplies will enter current limit at exactly their output current--they almost always limit current at a higher load current.

    What is the maximum output current you need from this supply?

    The TPS62140A is a simpler device with a smaller tolerance on its current limit.
  • 0 in reply to Chris Glaser
    Intellectual 280 points
    Hi Chris,

    Thank you for your reply.

    Yes, the design is for max 1.5A Output current . can you advice what should be a normal tolerance? on our tests, we measured max output load current of average 2.5A which reflects 66% more.

    in addition, if assuming the relevant tolerance, can you advice which components control the output current limit from the webench design I sent?

    as for the alternative ic, for now we would like to evaluate the current issue, Thanks for suggesting.

    Regards
  • 0 in reply to or nsl
    TI__Guru*** 146030 points
    I think the TPS54228 D/S has a thorough description of when the current limit starts to operate on pages 9 and 10. If there are questions about this, please be specific.

    The tolerance for the threshold itself is shown on page 5. It is a 2A rated device, which is already 33% more than you need.