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300mA to 500mA current limit needed for 5V output

Toshiya Hiramatsu
Intellectual 630 points
Other Parts Discussed in Thread: LM2575, TL431, TLV431, TPS2552, TPS5410

Hi,

I have a question for the way of current limiting.

I'm using LM2575.
I'm looking for the way of limiting the current by using an external circuit.
The limiting current value is between 0.3A and 0.5A.
I hope for the simple expedient.

Could you please teach me?
For instance, how about Fig-28 in the TL431 data sheet?


Thanks & Regards,
Toshiya.

  • 0
    TI__Guru**** 150770 points

    The best option will depend on what voltage you want to current limit.  What is the output voltage of your LM2575 circuit?

    Yes, the TL431 circuit will work as a current limiting circuit.  However, using the TLV431 will be twice as efficient, as it has a lower Vref.

    TI also offers a broad protfolio of current limited switches.  You can look through those here: http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=423&uiTemplateId=NODE_STRY_PGE_T

  • 0 in reply to Chris Glaser
    Intellectual 630 points

    Hello! Chris-san,

    Thanks for your quick response and advice.
    I'll use LM2575 by output=5V and input=12V.

    I'll try to see the web page.

    Thanks & Regards,
    Toshiya.

  • 0 in reply to Toshiya Hiramatsu
    TI__Guru**** 150770 points

    Yes, with a 5V output, you have many options.

    This is really a power interface question, so I will move this post to the power interface forum.  They can help recommend the right part.

  • 0 in reply to Chris Glaser
    TI__Expert 7990 points

    The TPS2552 is a programmable current limit protection device designed for 5V rails (e.g. USB and so forth).  It  has better accuracy than you requested.  The TPS2552 would be put on the output of the switcher. 

    Make sure that the switcher output ripple is well controlled so as to not have a large influence on the programmed current limit.  This would be caused by large converter ripple applied to large, low ESR capacitors downstream from theTPS2552 causing large switcher ripple to want to flow through the TPS2552.  In mathematical terms, Z(switcher output caps) << Z(load) at the swithcher fundamental frequency. 

    I suspect that you were thinking of placing the TL431 limiter on the input side of the switcher.  You might find there are issues with switcher startup and input ripple current affecting the desired operation.

    The switcher you have chosen seems to be a little older, considering the rapid advances in switcher ICs.   A shortcut to a selector guide is through www.power.ti.com which has a quick selection tool at the top (12V -> 5V @ 1A).  I found the TPS5410 there as a similar, but more advanced part.  This has an internal MOSFET, and there were also controllers there that might be of interest.

     

  • 0 in reply to Martin Patoka
    Intellectual 630 points

    Hello! Martin-san,

    Thanks for your response and detail explanation.

    I think that TPS2552 is good!
    I would introduce TPS2552 to the customer.

    By the way,I was thinking of placing the TL431 limiter on the output side of the switcher.


    Thanks & Regards,
    Toshiya.