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FDC2214EVM: Four channels with different oscillation frequencies share one sensor

Will
Prodigy 250 points
Part Number: FDC2214EVM
Other Parts Discussed in Thread: FDC2214

Dear TI experts,

I am trying to use the FDC2214EVM to evaluate the change in dielectric properties of materials under different frequency strains.

According to the datasheet of the FDC2214, each channel is activated in sequence.

So, does the design of the FDC allow four channels to share the same sensor like the figure below?

Or is an external multiplexer required here to avoid connections between channels?

Or do I need multiple FDC chips to get multi-frequency test results in one sweep?

Best regards,

Will

  • +1
    TI__Genius 17690 points

    Hello Will, 

    Connecting multiple channels together like this will cause the LC tank on other channels to become part of the measurement. Even using multiple FDC chips, you would still see this happen since other channels LC tanks will be connected. You could mux the channels similarly to how the TIDA-01102 reference design does. However, using the same sensor with multiple channels, cycling through the mux inputs would not be as clean of a solution since you should pause the device operation each time you change the mux which will slow down your sample rate. If this is the approach you take, I would suggest using single channel activation mode and switching the active channel each time you change the mux selection. 

    Lastly, I will mention that the FDC2214 is best when used to measure a change in frequency of the sensor rather than absolute measurements. 

    Best Regards, 
    Justin Beigel

  • 0 in reply to Justin Beigel
    Prodigy 250 points

    Thanks Justin, this is very helpful.

    Will