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current limiter and fold buck

Tsukui Yusuke
Guru 21930 points
Other Parts Discussed in Thread: LM25085, LM5166

Hi,

Customer wants the power supply to perform the following operations.

Customer condition ;
・Vin=6～12V
・Vout=5V
・Iout=200mA

Desired operation;
・Customers want to limit current at 200 mA.
・If it exceeds 200 mA, the customer wishes to lower the output voltage.
　(Image of foldback operation.)
    ex,Iout=200mA→Vout=5V Iout=250ｍA→Vout=2～4V

Could you tell me the recommended products?

Best Regards,
Yusuke/Japan Disty








  • 0
    TI__Guru**** 191445 points
    Yusuke,

    You can look at LM5166. It has a setting for 500 mA peak current limit, recommended for 200 mA load. If you need something more precise, you may have to look at a controller, maybe LM25085. Let me know if either of those choces will work for your application.
  • 0 in reply to JohnTucker
    Guru 21930 points

    John-san,

    Thank you for your response.
    Please excuse my lack of explanation.
    Customer wants to operate constant current at 200 mA.

    If it exceeds 200mA, the customer wants to control the constant current.
    In addition, customers want to lower the output voltage.

    Best Regards,
    Yusuke/Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Guru**** 191445 points
    Yusuke-san,

    If you design a constant current control circuit, then the output current is fixed and the output voltage varies to keep the current constant. Can you tell me more about your application?
  • 0 in reply to JohnTucker
    Guru 21930 points

    John-san,

    Thank you for your comment.
    Application is card leader module.
    Therefore, there is a variation in the input voltage spec.
    Thank you for introducing constant current control circuit.
    However, customers want to realize it on one chip or two chips.

    Customer is looking for an DCDC converter with brick-wall current limit protection as the next plan.
    Overcurrent limit in this plan want to 200mA.
    Could you please introduce the brick-wall current limit type efuse or DCDC converter?

    Best Regards,
    Yusuke/Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Guru**** 191445 points
    Yusuke-san,

    The parts that I support will all have relatively wide tolerance on the current limit. With constant current control, you are regulating to a fixed current. The only way to exceed it is if the load drops to so low of an impedance that the supply output rails out at its lowest level. In that case I suppose you may want a fail safe current limit. do you know the maximum range of load impedance? A well designed control loop may have enough dynamic range to limit the current naturally to always be 200 mA over your entire range of load conditions. If you absolutely need additional current limit, since you will be sensing current anyway, you may be able to clamp the output of the sense amp or use it's output to shut down the converter in case of an over current condition. Let me see if there are any reference designs for this type of circuit.
  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points
    Yusuke-san,

    Do you need any further assistance? Please let me know.