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FDC2114: Clarifying how the sensor works

Evan Archibald Meikleham
Prodigy 80 points
Part Number: FDC2114
Other Parts Discussed in Thread: LDC2114

I asked a question a few days ago and got partial clarification. I want to make sure that I understand the mechanism that the LDC2114 is using. As I understand, a current source drives the LC circuit, and it uses the zero-crossings and the known value of L to back out the value of C. (I've drawn out what I believe the mechanism is... though if this is right, the frequency is sqrt(LC) instead of the usual value of omega = 1/sqrt(LC))

  • 0
    TI__Mastermind 23810 points
    Evan,

    What you are missing is that the current source is an AC source. It pushes back and forth across the circuit.

    There are two pieces to it:
    - drive the circuit at its resonant frequency (this is done how I described before)
    - measure the resonant frequency by comparing it to a reference frequency