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FDC2212: FDC2212 APPLICATION

Jack LEE
Prodigy 80 points
Part Number: FDC2212

Hello, Could I used the FDC2212 this way? Two channels connect to the same two plates.  Now the LC result in a 6.5M oscillation, but I want to get a frequency between 300k and 1M, which value of LC do you

recommend? And I want to use fdc2212 two channels one is 6.5M and the other is between 300k and 1M, but they both connect to the same two plates. Because currently my sensor is sensitive to different frequency

field for different parameters, so I want to use it this way. Is it feasible or not? thank you for your reply.

  • 0
    TI__Genius 17440 points

    Hi Jack,

    Although your LC tank yields a sensor frequency of ~6.5MHz, the additional filter capacitors will bring the sensor frequency down to ~4.5MHz. If you want to further reduce the sensor frequency you can increase either the L or C values.

    You definitely should not connect two different channels to the same sensor plates. When one channel is actively driven, all others are internally shorted to GND. The FDC will not be able to drive either channel if you short them together. If you need to use the same sensor plates, I suggest using a 2:1 MUX in between the LC tanks and the plates. Note that the FDC does not support sensor hot-swapping, so you'll need to put the FDC in sleep mode when the MUX switches.

    Best Regards,

  • 0 in reply to Kristin Jones93
    Prodigy 80 points

    Okay, Now I got the problem. But what if I want to get a 300k-1M frequency, Is there some recommendations?   Thank for the reply.

  • 0 in reply to Jack LEE
    TI__Genius 17440 points

    Hi Jack,

    Just experiment with changing the LC values in the equation until you find a sensor frequency that works for your application. You can always check common values that are easily obtainable. 

    Best Regards,