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TLV62595: minimum inductor DCR value

Josh Heiner
Intellectual 860 points
Part Number: TLV62595

Hi,

I've been working with a new TLV62595 design, and I noticed that WEBENCH recommends using an inductor with a minimum DCR value of 5 mOhm.

I was a bit surprised by this as I could find no mention at all of a minimum inductor DCR value in the part's datasheet.  Can someone from TI elucidate?  What would be the negative effect of using an inductor that has a DCR lower than this value?  I tried making a custom one with a lower DCR, and it still seemed to work in the simulation at least.

Thanks,

Josh

  • 0
    TI__Intellectual 2040 points

    Dear Josh, 

    Thank you for your enquiry.

    The DCR (direct current resistance) of an inductor is the resistance of the wire used to wind the coil of the inductor. A lower DCR value for an inductor means that there is less resistance in the wire, which can result in less power loss in the inductor.

    The minimum DCR value recommended by WEBENCH is designed to ensure that the inductor is able to handle the current without significant losses and also to maintain the efficiency of the converter. The recommended minimum DCR value is a conservative value and using an inductor with a lower DCR value may still work, but it is not guaranteed to work in all cases.

    In summary, the recommended minimum DCR value for the inductor in the TLV62595 design is intended to ensure that the inductor can handle the current without significant losses and maintain the efficiency of the converter. 

    Thank you,

    Rameen 

  • 0 in reply to Rameen
    Intellectual 860 points

    Thanks for the quick response, Rameen.

    I am certainly in agreement that core losses need to be considered in a complete evaluation of factors that affect an inductor's contribution to efficiency, but of course WEBENCH is a rather simple tool and doesn't give us a way to do that.  I have never seen any kind of direct relationship between DCR and core losses, or even a general trend; it seems a bit counterintuitive to me.  I think of core losses primarily as a function of the core material and the frequency of operation.  It sounds like TI might have observed that secondary or tertiary factors affecting core losses (winding packing efficiency inside the core, perhaps?) tend to increase in inverse proportion to DCR.  If so, I have never noticed this before.

    For my own enlightenment, do you know of a reference (web page, white paper, app note, or blog) that explains this relationship in more detail?

  • 0 in reply to Josh Heiner
    TI__Intellectual 2040 points

    Dear Josh,

     

    Thank you for pointing that out. You are correct, DCR losses and core losses are independent of each other. A low DCR value indicates that the inductor has low resistance and can efficiently transfer power from the input to the output of the circuit.

     

    As mentioned, the WEBENCH design tool recommends a minimum DCR value of 5 mOhm for the TLV62595 to ensure optimal performance and efficiency of the power supply circuit. Therefore, using an inductor with a DCR lower than the recommended value may not have any negative effects on the circuit, but it may not provide the most cost-effective or solution-size efficient option.

    Thank you.

    Best Regards,

    Rameen