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LM25085: Current limit during runtime.

Nikhil Anjane
Prodigy 90 points
Part Number: LM25085

Hi,

Can I change the current limit for LM25085 during run time?

What I want to achieve is to keep the output voltage constant and just vary the output current. Is such configuration possible with LM25085?

Regards,

Nikhil Anjane

  • 0
    TI__Expert 5301 points

    Hi Nikhil,

      A well designed Buck circuit can output a constant and stable voltage. But the output current is depend on the load. 

      Current limit can be adjusted by configuring  different  Radj , it is used for overcurrent protection, not for load controlling. I think you may vary the output current by adjusting the load. 

      If I misunderstood your question, please kindly figure it out. Thanks.

    BR,

    Victor

  • 0 in reply to Victor Yu
    Prodigy 90 points

    Hi Victor,
    The load I am using is capable of drawing 6A current at 7V.
    I want to keep the output voltage constant at 7V and then set current limit within range 1A-6A for the load. So that at any given time the maximum amount of current available for the load can be dynamically set. 

  • 0 in reply to Victor Yu
    Prodigy 90 points

    Hi Victor,
    The load I am using is capable of drawing 6A current at 7V.
    I want to keep the output voltage constant at 7V and then set current limit within range 1A-6A for the load. So that at any given time the maximum amount of current available for the load can be dynamically set. 

  • 0 in reply to Nikhil Anjane
    TI__Expert 5301 points

    Hi Nikhil,

      Sorry for the delay because of the weekend.

      I think what you need is a adjustable CC/CV buck. I don't recommend using current limit to realize CC/CV. As I mentioned before, current limit is used for protection. I don't know much details  about your  load, but for some kinds of loads. Current limit may lead to the drop of output voltage. You may need to double check if your load current can be limited while the output voltage is constant.

      The following link introduced about CC/CV buck with LM25085.https://www.ti.com/lit/an/snva486a/snva486a.pdf 

    BR,

    Victor

  • 0 in reply to Victor Yu
    Prodigy 90 points

    Hi Victor,

    Thanks for the inputs. My load is a motor actually.
    But, as the pdf says for proper current control I will need to add external ciruitry.

    Regards,
    Nikhil

  • 0 in reply to Nikhil Anjane
    TI__Expert 5301 points

    Hi Nikhil,

      Yes, some extra circuitry are needed to design a CC/CV buck. You can test on your demo board and motor load to check if a normal CV buck can control the output current by current limit.

    BR,

    Victor