Hello,
we are using LDC1000 on a project where the PCB coil is the same of the LDC1000EVM (we used the Texas gerber file). All of the components of the circuit are the same of the EVM. The only difference is that in our sensor VDD = VIO = (short circuited) 5V.
Ctank is also the same of the LDC1000EVM, so we have a resonance frequency of approx. 3.6MHz. We need to reduce this frequency due to increase our ODR range to reach better precision, defined as:
DELTA ODR temperature
precision = ----------------------------------------
DELTA ODR calibration range
Since we can not change the L value, we can only change the Ctank value.
We tried on the LDC1000EVM incresing the Ctank up to 35nF (200kHz resonance frequency). Over this value the LDC circuit does not working.
On our application we can't go over 500pF.
Why this difference? Maybe the VDD = VIO can cause this differnce? Have you any suggestion? How to maximize ODR range without to modify the target position?
Best regards