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LM25010 current limit

Diogo Rebelo
Prodigy 110 points
Other Parts Discussed in Thread: LM25010, LM25011

Hi,

This is my first post in this forum so i'm don't be shure if i am in the rigth place.

 I'm worked with a LM25010 and i want to limit the output current, but in datasheet they say if i want to change the limit current i must chose the indutor ( i chose 10uH), but in webench simulation the current don't go to 300mA, it goes to the maximum (1A). 

What i'm doing wrong? Can you tell me? 

Thanks the best regard

  • 0
    TI__Mastermind 31580 points

    Hi Diogo

    Your post belongs in the non-isolated forum. I am going to move it and one of my colleagues will pick it up there.

    Regards

    Peter

  • 0 in reply to Peter Meaney
    TI__Guru**** 191445 points

    For LM25010 the current limit is set internally at 1.25 A typ.  You can increase it but you cannot decrease it.  it is valley detect current limit, so the maximum load current in current limit operation is Ucl + ILpp/2.  Increasing the inductor value will lower ILpp and thus lower the maximum load current during OCL, but not below the OCL threshold.

  • 0 in reply to JohnTucker
    TI__Intellectual 1435 points

    Diago,

    The LM25010 does not support adjusting the current limit to a lower value.   The output current is limited by monitoring the current in the rectifier D1 when the high side buck switch is off.  If the current in the rectifer exceeds 1.25A (typical),  the buck switch is held off until the current decreases.    The current limit can be adjusted upward by connecting a resistor from ISEN to RTN in parallel with the internal 130mohm current sense resistor.  The current limit cannot be decreased.

    You might consider the LM25011.   It is a similar device with external current sense resistor.   You should be able to adjust the current limit from the maximum 2A to relatively low values.