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FDC1004-Q1: extending capacitive input range

daivid daglass
Prodigy 70 points
Part Number: FDC1004-Q1
Other Parts Discussed in Thread: FDC1004, FDC2214

Hi,

I am going to use FDC1004 for more than 100pF  capacity measurment. Is there any circuit or solution to extend capacitive input range like AD7745 IC from Analog Device?

Best regards,

Mehrdad

  • 0
    TI__Expert 8050 points
    Hi Mehrdad,

    The resonance-based FDC2214 has a much wider input range than FDC1004.

    Alternatively, if you prefer to use FDC1004, you can connect a capacitor with a known value to the input pin, and connect the sensing capacitor in series with it. The FDC1004 would then measure the effective capacitance of the two capacitors in series.

    Regards,
    Yibo
  • 0 in reply to Yibo Yu
    Prodigy 70 points
    Hello Yibo,

    Thank you for your soltion.
    Could you please tell me about FDC2214 resoltion. I read its datasheet all but I didn't find anything abot it.

    Thanks,
    Mehrdad
  • 0 in reply to daivid daglass
    TI__Expert 8050 points
    Hello Mehrdad,

    The effective resolution for capacitive sensing is always system-dependent. You can let the FDC run in your system, and monitor the fluctuation of the output data stream.

    It is possible to achieve better solution with FDC2214 than FDC1004. To get the best resolution out of FDC2214, you should use a small capacitor in the LC resonator. However, the tradeoff is that the output data would be less stable with a smaller capacitor and additional data processing may be needed.

    Regards,
    Yibo