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LDC1614: adding a fixed series inductor, how to select inductor value

Amy Luo
Expert 6895 points
Part Number: LDC1614

Hi team,

The customer has the following questions:

Read an article published by Ben kasemsadeh, which is linked as follows. It is said that the inductance should be connected in series when the coil size is small.

https://e2e.ti.com/blogs_/b/analogwire/posts/inductive-sensing-how-to-use-a-tiny-2mm-pcb-inductor-as-a-sensor

Due to the limited space, the designed coil has an outer diameter of 2mm, two-layer plate, line width, line diameter of 3mil and plate thickness of 1mm. The capacitance of 10nF was used, and no response was tested with LDC1614EVM. Can this phenomenon also be solved by connecting an inductor in series? How to select inductors in series?

Best Regards,

Amy Luo

  • +1
    TI__Mastermind 40295 points

    Amy,

    Some of the sensor parameters aren't mentioned, like the sensor inductance and the desired oscillation frequency.

    The first step would be to find out those values, and calculate the required Rp and C.
    If the Rp is not between the absolute minimum (250Ω) or the max (100kΩ) values, then  series inductor as the note suggests may be a potential solution.

    A starting point for the series inductor could be to choose an initial part based on readily available shielded inductors.
    With that first part, use Lsensor+Lseries to calculate the C for the required sensor frequency and the resulting Rp.
    If values agree with datasheet limits, then you will have a starting point for EVM experiments. 

    If Rp doesn't meet data sheet limits, then try other values for series inductors and step thru the calculations until you find a set of candiadate values.

    Please let me know if you have any questions.

    Regards,
    John