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FDC2214: Recommendations to mitigate crosstalk between multiple FDC chips

Dylan J.
Prodigy 140 points
Part Number: FDC2214
Other Parts Discussed in Thread: FDC1004

Hello,

I'm working on an application that involves >4 channels, so it would require the use of at least two FDC2214 chips.

While the 4 channels of each chip are offset in time, there's no way to synchronize between two of them to make sure they aren't exciting their sensor lines at the same time.

While shielding could help with crosstalk, the sensors do have to come in fairly close proximity to each other.

If the LC tanks on each were to be configured to have different base frequencies, such that the resonant frequencies would not overlap over the sensor variable range, would that be an effective way to mitigate crosstalk? Is there a better way?

E.g. FDC0 has 18uH/33pF tanks and FDC1 has 18uH/20pF tanks. If they both have the same sensors with ranges that don't overlap in terms of total tank capacitance, they should never occupy the same frequency range.

Thanks!

  • 0
    TI__Expert 7599 points

    Hi Dylan,

    Certainly having each FDC with different frequency can help minimize cross talk and also please make sure that you are able to control the multiple FDCs and that no 2 FDCs chips are on at the same time. 

    Shielding will help. Advanced EM simulation modeling of parasitics across the sensors will reveal if there are potential noise introduction due to radiation from the inductors. Capacitive sensing in general is challenging as air can be considered as a dielectric and changes in environment could result a change in capacitance. 

    We dont have any EVMs or product demos that can help provide specifics on multi FDC operation. 

     

  • 0 in reply to Arjun_Prakash
    Prodigy 140 points

    Hi Arjun,

    Thanks for the response. The purpose of this question is to enable two FDCs to run simultaneously with minimal crosstalk. Since they have a configurable I2C address bit, two can be on the same I2C bus by design. Can you please explain why no 2 FDC chips should be on at the same time?

    Thanks,

    Dylan

  • 0 in reply to Dylan J.
    TI__Expert 7599 points

    Hi Dylan,

    The FDC devices works on the principle of resonant architecture... When 2 FDCs are on simultaneously there can be a potential to cross talk and mutual coupling and that can introduce errors into the system. Your question in regards to shielding is valid and needs to be considered and avoiding enabling multiple FDC would minimize the crosstalk. 

  • 0 in reply to Arjun_Prakash
    TI__Expert 7599 points

    Also, if you are concerned about the cross talk due to FDC2214 architecture of resonance I would consider the FDC1004 instead as its architecture is based on a cap-to-digital output converter.