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Original question:

Webench coil designer

WEBENCH® Tools/LDC1612: LDC1612

Dinesh Kumar2
Prodigy 120 points
Part Number: LDC1612

Tool/software: WEBENCH® Design Tools

Good day!

I have designed a Circular Coil PCB with the help of Webench designer tool. The input parameters are in the image for your reference. 

  1. Does the output inductance, Q-Factor, DC coil resistance differs according to the input temperature? (Pls refer the attached images for the changes in the output against the change in temperature)

  2. What does the temperature field in the input side refers? Temperature at which stage to be entered here?

  3. As I don't have any instruments to measure and verify the output are as per my design (say inductance, Q-factor..) I only rely on the DC coil resistance of the manufactured sensor PCB. If the Coil's DC resistance is close to the output DC resistance I derived using webench design tool, then I consider it as ok. Please guide me and correct if I am wrong.

  4. I need to set the exact drive current to nullify the Inductance conversion noise. Please suggest a simple method to achieve this. The PCB has been manufactured as per the regulations and standards, but still my coil inductance and relative frequency drifts.

Please give detail clarification on all the above points. It will be very helpful.

Thanks & Regards,

Dinesh

  • 0
    TI__Genius 17440 points

    Hello,

    1. Yes, the inductance, Q factor, and series losses (both AC and DC) of the coil will change with temperature.

    2. This is the temperature of the coil when it is being measured.

    3. I would not recommend using this approach. Coils can have significantly different inductances with the same DC resistance. It would be better to measure the resonant frequency of the sensor when the LDC1612 drives it. If you use capacitors with tight tolerances, you should be able to estimate your coil's inductance. I'd recommend using the output codes of the LDC and not an oscilloscope.

    4. The simplest method to do this is using an oscilloscope. Set the drive current so that the sensor oscillation amplitude is between 1.2-1.8V for the entire range of target motion. You can read more about this method in this application note.

    Best Regards,