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TPS53319 Inductor DCR Question

David Wang11
Expert 7400 points

Other Parts Discussed in Thread: TPS53319

We have a customer that is trying to use Webench for the TPS53319 with a coilcraft inductor, XAL6030-561ME (0.56uH). The tool that gives the compensation for the switcher, does not like the indcutor DCR value (saying the loop may be unstable). They thought that tool would compensate through the feedback.

The coilcraft inductor has a DCR about 10 times greater than the max the tool allows. DCR would essentially affect efficiency, but how does that affect stability?

Any thoughts on this webench design?

Input Voltage: 10-14V

Output Voltage: 1.23V

Output Current: 14A

  • 0
    TI__Intellectual 1370 points

    Hi David,

    Which tool are you referring to here that says that the loop is unstable?  Are you simulating this design in some tool? For the inductor selected by WEBENCH, DCR value is as per the datasheet.

    Please let me know which tool(s) are you talking about.

    Regards,

    Pavani Jella

    WEBENCH® Applications 

  • 0 in reply to Pavani Jella
    TI__Expert 7400 points

    hi Pavani

    I am referring to webench. You can change the default components to different selections and the customer is putting in a customer inductor. The inductor they want to use is much higher than the max that is allowed from webench because it says that it may cause instability.

    We are trying to figure out why that would be the case, because DCR is associated with mainly efficiency. The customer believes that the loop compensation would just take the DCR into consideration and adjust the compensation network accordingly....

  • 0 in reply to David Wang11
    TI__Intellectual 1370 points

    Hi David,

    Ok, now I get it. I am looking into the custom component option for inductor. I will check what is going on and get back to you soon.

     

    Regards,

    Pavani Jella

     WEBENCH® Applications

  • 0 in reply to David Wang11
    TI__Intellectual 1370 points

    Hi David,

    I recreated the design using TPS53319 with customer specs, updated the inductor to  XAL6030-561ME. Input 0.56uH as inductance, and DCR as 3.1mOhm, and I see the pop up that warns about instability. The reason for the pop-up is that, for the WEBENCH generated design, the max limit for DCR is 0.8mOhm.  This, because WEBENCH does not currently re-calculate the compensation and we cannot gaurantee stability in the design with custom components.

    However, we are working on this feature, as we speak. Pretty soon, we hope to have re-compensation calculator activated in WEBENCH, where customer can change critical components and re-design compensation. 

    Sorry for any inconvenience caused. Please let me know if I can be of further assistance.

    Regards,

    Pavani Jella

    WEBENCH Applications