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FDC1004 Shield Driver: Daisy Chaining Shield Signal

Clinton Burns
Prodigy 135 points
Other Parts Discussed in Thread: FDC1004

Hello,

I am planning on using the FDC1004 to measure the change in capacitance in a custom sensor I have made which can be seen in the attachment. My plan was to run a wire from the shielding on the cable that is attached to the SHLD1 pin on the FDC1004 to the shield layer seen in the attachment so that each layer is isolated from the layer next to it. My question is am I allowed to power the shield separating the layers from the shielded cable I am using?SensorLayoutIdea.PDF

  • 0
    TI__Expert 8050 points
    Hello Clinton,

    Those shield layers may not work well because they are right next to the ground layers. In fact, ground layers themselves can serve to shield the signal layers from each other.

    Regards,
    Yibo
  • 0 in reply to Yibo Yu
    Prodigy 135 points
    My fear was that the capacitance from the signal layer would be effected by the ground of the layer above it. So you are saying that this would not be an issue?
  • 0 in reply to Clinton Burns
    TI__Expert 8050 points
    Hi Clinton,

    Depending on the material and dimension of the support material and dielectric material, you can analyze the relative strength of the capacitive coupling of the signal layer to the layer above and below it. You can also try experimenting with the shield layer, but you'll need some dielectric between the shield and ground layers.

    Regards,
    Yibo
  • 0 in reply to Yibo Yu
    Prodigy 135 points
    Thank you for the help. Why exactly would I need a dielectric material between the shield and ground layers? My thinking is that would create a capacitance between the two layers which is not what we want.
  • 0 in reply to Clinton Burns
    TI__Expert 8050 points
    Hello Clinton,

    If you don't have separation between them, your shield would be shorted to ground.

    Regards,
    Yibo