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LMR10510X: Is Webbench right to recommend Inductor for Decoupling Circuits?

Clemens Koller

Hello!

Switching Regulator: LMR10510X
Vin=5V
Vout=3.3V
Iout=1A max

Design targets: low cost, small size.

Webbench suggests here the following inductor: TDK NLC32T-4R7M-PFR
But his inductor is optimized for Decoupling Circuits and might have higher loss as
bulk inductors.

Is this inductor really good to use for SMPS purposes?

Thanks,

Clemens Koller
Embeon SDE

  • 0
    TI__Intellectual 1825 points

    Hello Mr. Koller,

    This TDK inductor suggested by WEBENCH is not suitable for SMPS purposes.  Thanks for bringing this to our attention.

    I tried to create a design in WEBENCH using the design requirements you specified, and was unable to bring up this inductor.  Did you just enter in 5V as the minimum and maximum Vin or is there a range you entered for the design?  Also, which optimizer option did you turn the knob to? Was the knob turned to '1' for Smallest Footprint or '2' for Lowest BOM cost?  

    If you could provide more details on the design inputs you used to bring up this inductor, we would greatly appreciate it since it would help us tweak our calculations to prevent these types of inductors from being picked up for WEBENCH designs.  

    Regards,

    Jonathan Arzadon
    Applications Engineer
    WEBENCH Design Center 

  • 0 in reply to Jonathan Arzadon

    Here are the parameters entered into the ti.com Webbench:

    Vinmin=4.9V
    Vinmax=5.1V
    Vout=3.3V
    Iout=0.5A
    ta=30degC
    Optimization=3 (default)

    All other parameters left to defaults.

    I have chosen the uppermost 1.6MHz LMR10510X design.

    Footprint=108mm^2
    BOM Cost: $0.56 (obviously a lie)
    Efficiency=90%

    The recommended Inductor is a TDK NLCV32T-4R7M-PFR

    The link on top of that page is:
    http://webench.ti.com/webench5/power/webench5.cgi?base_pn=LMR10510X&Flavor=none&AppType=None&topology=Buck&optFactor=3&VinMin=4.8&VinMax=5.2&O1I=1&O1V=3.3&op_TA=30&application=SWITCHER
    (which doesn't fit to my entered values as I have changed it in Webench after the first run)

    Screenshot attached (despite bad layout).

    I would bet that the circuit even works, as this inductor is a medium quality Q=15(typ.) type.

    Anyway, the NLCV32T series is really cheap, but it melts away quickly if the reflow is done just a tiny bit too hot...

    Regards,

    Clemens Koller
    Embeon SDE

    Screenshot:

  • 0 in reply to Clemens Koller
    TI__Intellectual 1825 points

    Mr. Koller,

    Looking at all the alternate inductors suggested by WEBENCH, the NLCV32T-4R7M-PFR was selected for the design because it was cheaper and smaller than some of the other options.   

    If you would like to select a different inductor for your design, you can use the "Select Alternate Part" option in the Bill of Materials window and select a different inductor there.

    Also, the pricing that we list in WEBENCH is fairly accurate, since the component pricing comes from a live feed provided by many of the distributors.

    Let me know if you have any other questions or concerns. 

    Regards,

    Jonathan Arzadon
    Applications Engineer
    WEBENCH Design Center