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FDC2112: Differential vs single ended sensor

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Replies: 5

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Part Number: FDC2112

Hi! My application for the FDC2114 involves capacitance sensing of two pads that are spaced <5um apart. The datasheet says:

The single-ended configuration allows higher sensing range than the differential configuration for a given total sensor plate area. In applications in which high sensitivity at close proximity is desired, the differential configuration performs better than the single-ended configuration.

Could you elaborate on why the differential configuration performs better? Thank you!

  • Hi,

    In the differential configuration, two conductive plates are connected to IN0A and IN0B. This results in a higher change in frequency for the same change in distance in the target object compared to single-ended configuration. So, differential configuration performs better at close proximity.

    Regards

    Sharath.

  • In reply to Sharath Vallamkonda:

    It seems as though this would just require twice the electrode area, so its not actually increasing the sensitivity/area? I'll need to work out the equations to support this. Is that already done?

    Thank you. 

  • In reply to ikellymo:

    I should add that all I am trying to do is gain as much sensitivity as possible from about 3pF total variation. I currently see about 5fF resolution on the FDC2114 with the gain maxed out.

    Considering the below drawing with possible configurations (A) to (F), wouldn't (F) be the most sensitive, for a given area with sensor capacitance of 2C2? In differential configuration (C) there is 1/4 the sensitivity?

  • In reply to Sharath Vallamkonda:

    Please see additional details below

  • In reply to ikellymo:

    Hi,

    Yes, you are correct, F would be the most sensitive. We generally recommend differential sensor mode as it is a balanced sensor system where we measured lower noise with higher resolution.

    Regards

    Sharath.

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