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LDC2114EVM: 4 layer PCB, LC watchdog error

Part Number: LDC2114EVM
Other Parts Discussed in Thread: LDCCOILEVM, LDC2114, LDCTOUCHCOMCOILEVM

I'm using the LDC2114EVM and trying to use a 4 layer coil as the sensor ( coil "L" from the LDCCOILEVM PCB) 

When viewing the output in the Data Streaming tab of the Sensing Solutions EVM GUI the status data toggles between a value of 64 and 68 due to the LC watchdog error bit being set and cleared. Whilst the value of data0 remains at 0.

are there any suggestions for the tank capacitor value or for which register bits need to be set for this to function?

Many Thanks. 

  • Hello,

    You will likely need to adjust the SENSOR0_CONFIG, LC_DIVIDER, and CNTSC registers to be appropriate for your sensor.

    According to the LDCCOILEVM user guide, coil L has an inductance value of around 55µH. By default the LDC2114EVM has a sensor capacitor of 47pF and pin input capacitance of 17pF. The expected oscillation will be around 2.7MHz as a result. You can use the LDC2114_Config_Tool tab of our LDC tools spreadsheet ( www.ti.com/.../slyc137 ) to give you a good starting point:

    Note that we also offer the LDCTOUCHCOMCOILEVM ( www.ti.com/.../LDCTOUCHCOMCOILEVM ) which is specifically designed for the LDC2114 and includes the appropriate sensor capacitor selection and register settings in the user guide.

    Regards,

    Luke

  • Great, that's working now.
    Thanks.