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Original question:

FDC2114EVM: About settings

FDC2114EVM: Optimization of inductor and configuration

user6328993
Prodigy 50 points
Part Number: FDC2114EVM
Other Parts Discussed in Thread: FDC2114,

Hi, TI

FDC2114EMV has 18μH inductor on the board.

When I want to measure  500pF～1500pF, what size inductor do I use?

And, when I use the optimal inductor to measure 500pF～1500pF, what are the optimal settings for the followling parameters?

- offset

-Deglitch filter

-F ref

-Settle Count

-Reference Count

-I drive

and so on.....

Best regards,

Umemura

  • 0
    TI__Mastermind 40295 points

    Umemura-san

    Please take a look at the section in the FDC2114 data sheet titled Detailed Design Procedure (10.2.3).

    It makes recommendations for calculating component values and register settings for a liquid-level sensing application, but it should help. 

    Other info that may be helpful can be found in the FDC2x1x Capacitive Sensing FAQs:
    e2e.ti.com/.../976712

    The FAQ page shows supporting app notes and technical articles which should be helpful.

    Please let me know if you have any questions.

  • 0 in reply to John Miller - Sensing
    Prodigy 50 points

    Hi, John-san

    Thank you for your reply.

    I followed your advice and changed the settings of FDC2114EVM.

    I've changed "Data Offset" to zero, and "Idrive" to 307μA.

    Then I was able to measure down to 0.022μF.

    However, I was not able to measure the capacitor above that value.

    I ask the following questions.

    What do I need to do to measure capacitance above 0,022μF?

    Do I need to change the value of the inductor?

    Best regards.

  • 0 in reply to user6328993
    TI__Mastermind 40295 points

    Umemura-san,

    Page 19 of the data sheet shows some design equations that take into account the inductor , the sensor capacitance and the resonant frequency.

    Is it possible in your system to adjust the inductor value and possibly the resonant frequency to adjust the range of measured capacitance?