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LDC1612: About LDC_tools , LDC161x-LDC131x_Config Tab Questions

user5203911
Intellectual 560 points
Part Number: LDC1612

Hello

 

Why is the calculated frequency in the LDC161x-LDC131x_Config tab so different from the calculated frequency in the Spiral Inductor Designer tab?

As an example, the frequency(Inductance) result at d=1.5 mm is as follows.

　LDC161x-LDC131x_Config tab 　3.9563MHz (L=4.9309µH)

　Spiral Inductor Designer tab　 3.363MHz (L=6.325µH)

As a result, The graph of Approximate Inductance vs. Distance Response seems to have different results.

Which tab has the correct result?

 

Conditions:

　LDC_tools: LDC_Tools-ext49.xlsx

　Coil specification: LDC1612EVM standard coil (φ=13.9 mm, 19T,)

　C=330pF

In the LDC161x-LDC131x_Config tab, Use setting from Spiral Inductor Designer is checked.

(Free-space Sensor Frequency =3.221MHz)

 

Best regards

LDC_Tools-ext49_test.xlsx

  • 0
    TI__Genius 17440 points

    Hello,

    The LDC161x tab of the calculator tool uses a slightly different target thickness than the Spiral Inductor Designer. At your sensor frequency, the target in the LDC161x tab is not quite 3 skin depths thick. This slightly weakens the inductive response compared to the target in the Spiral Inductor designer, which is at least 5 skin depths thick (we recommend a minimum of 3).

    Besides these differences, the Spiral Inductor Designer has been updated more recently, and there may be slight differences in the calculations. I recommend using the Spiral Inductor Designer's calculations. You can also use the Excel FEMM tool to verify these calculations. Keep in mind that these are all estimates, so there may be some small variations between these calculations and the real-world sensor.

    Best Regards,

  • 0 in reply to Kristin Jones93
    Intellectual 560 points

    Hello Kristin

    Thank you for your quick reply

    It was written that the Skin Depth used in the LDC161x tab is not 3, but is it less than 3?
    From the difference in the sensor frequency results between the LDC161x tab and the Spiral Inductor Designer tab, the skin depth on the LDC161x tab is likely to be only about 2.
    LDC161x-LDC131x_Config tab 　3.9563MHz (L=4.9309µH)
    Spiral Inductor Designer tab 　　3.363MHz (L=6.325µH)

    Originally, I would be grateful if these values were synchronized between tabs.

    Best regards

  • 0 in reply to user5203911
    Intellectual 560 points

    Hello Kristin

    I revise the content of the previous question.
    In the following, it was the mistake of the Spiral Inductor Designer tab, not the LDC161x tab.

    -----------------------------------

    It was written that the Skin Depth used in the LDC161x tab is not 3, but is it less than 3?
    From the difference in the sensor frequency results between the LDC161x tab and the Spiral Inductor Designer tab, the skin depth on the LDC161x tab is likely to be only about 2.

    ----------------------------------

    The large change in frequency means that the target thickness is sufficiently large for 3 Skin Depth.

    Does it mean that the aluminum target thickness in the Spiral Inductor Designer tab is thin compared to 3 Skin Depth?

    Best regards

  • 0 in reply to user5203911
    TI__Genius 17440 points

    Hello,

    My apologies for the delayed reply. The skin depth in the LDC161x tab is less than 3 at your sensor frequency. The skin depth of the target used in the Spiral Inductor Designer is at least 5 skin depths for any sensor frequency that the LDC161x can drive. The target in the Spiral Inductor Designer is thicker than the target in the LDC161x tab.

    I think that part of the difference between your results is that the calculations in the Spiral Inductor Designer have been updated more recently. I recommend using the Spiral Inductor Designer for your frequency estimations, and we will work on updating the LDC161x tool to match the Spiral Inductor Designer.

    Also please note that I have actually moved to a new group, so if you have any follow-up questions please post a new thread so that the current LDC engineers can support them.

    Best Regards,

  • 0 in reply to Kristin Jones93
    Intellectual 560 points

    Hello, Kristin

     

    Thank you for your reply.

    I understood.

    It means that LDC_Tools-ext49.xlsx as below will be updated soon.

    Inductive Sensing Design Calculator Tool (Rev. E)

    E->F ？

     

    I am hopeful for playing an active role at the new work group.

    Thank you for everything.

     

    Best regards