I recently created a small sensor board with a few small racetrack stacked coils (8 turns, 3.5mil traces, 3.5mil spacing, 1 oz copper, 6mm x 3.3mm). Each coil had its own LDC0851 on an accompanying control board.
Two of the coils were within 10mil of each other, and the other was about 160mil away. During testing i found the 2 coils that were next to each other were interfering with each other. Rather then turning on and off, they would function more like an analog out then a switch. (My LED would dim and brighten as the target approached/retreated).
I disabled one of the two coils, and the other two sensors would work perfectly.
We wanted the redundancy of two sensors for this application though, so we got the idea to try and drive two LDC0851 chips with just the one coil. Now my signal on the coil is in parallel with the signal input on two LDC0851's, and the same for the reference and common.
It worked, but every 10-20 times I toggled the sensor on/off it seemed to just overload and go into a non-functioning state. Powering down and powering up the devices brings it back. I was designing a new set of sensor boards and one of the ones we were trying was going to be a much bigger coil that would drive both of those LDC0851 chips, but I was hoping to understand what was overloading the chips so I can avoid it in the future attempt.
Thanks for any input.
