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FDC2214EVM: Input deglitch filter

Part Number: FDC2214EVM
Other Parts Discussed in Thread: FDC2214


I have a couple of questions regarding the "Input deglitch filter" setting in the EVM GUI. When setting the deglitch frequency to a value below the LC-tank frequency the frequency of the sensor is reduced from ~5Mhz to ~1.8Mhz.

Also the Idrive current needs to be increased to get to 1.2Vpk after this happens and the half-sine signal driving the sensor looks more like a full sine with pauses in between:

~ = full sine

~__~__~__~ and so on.

Something like the user in this post:

Is this by design? Are there any drawbacks? Is it possible to use the FDC2214 this way, or will it break (I have no idea of the internals)?  I ask this because it would be convenient for our application if I could use it with these settings.

  • Hi Tom,

    It is recommended to configure the FDC device as stated in section 9.3.5 of the datasheet:
    If the deglitch is set to a frequency below the LC tank resonant, the device will not operate properly.

  • Hey Rachel,

    I understand that operating the device in this way is not according to spec. That is why I ask the question, my measurements look good, but will it break the device?


  • Hi Tom,

    No, the device will not physically break but it definitely will not operate properly. The measurements will not be guaranteed to be accurate or stable. Is there a reason that improper device operation is desired?

  • Hey Rachel,

    Sorry for responding so late, I missed the notification email.

    Well the reason for my curiosity is that I happened to notice that the sensitivity is extremely high when tuning the sensor to a high frequency and setting the deglitch filter to a low frequency. The EVM GUI then reports a sensor frequency of about 2Mhz and resolution is increased. Measurements seem consistent and stable so far. Tuning the sensor to 2Mhz and correctly setting the deglitch filter does not yield the same result, sensitivity is about the same when doing this.



  • Hi Tom,

    How much difference is there between the deglitch frequency and your sensor frequency? I wasn't expecting this behavior - I tested it with one of our EVMs and the device was essentially spitting out garbage when the deglitch filter was set lower than the sensor frequency. Do you have any scope shots of the sensor waveform or other register settings that might further explain what else may be happening?

  • Hey Rachel,

    The sensor is tuned/designed for 6.1Mhz, this is also what is shown in the EVM GUI when the deglitch filter is set correctly. The output at INA0/B0 is a nice half sine wave.

    If I set the deglitch filter to 1Mhz the described behavior is observed and the output waveform changes to:

    It also seems that the "base" frequency of the sensor is important, when tuning for 8 or 10Mhz the "problem" does not occur.

    Contents of the registers.json file:





    Forgot to mention, the sensor is connected in differential configuration.