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FDC2214EVM: Under what conditions would FDC2214 EVM saturate?

Bhindhiya Raja
Prodigy 50 points
Part Number: FDC2214EVM
Other Parts Discussed in Thread: FDC2214

Hi all, 

I am trying to use the FDC2214 EVM board and would like to know -

1. The different conditions due to which the FDC might read a saturated capacitance value

2. How I could possibly check which one of these conditions is the cause for the saturation

Looking forward to your response as it would help me better understand and utilize the chip.

Thank you!

  • 0
    TI__Mastermind 40295 points

    Bhindhiya,

    Some of the potential causes of saturated readings:

    1. The LC oscillator reaches the edge of its supported range based on the values of the L, C and the overall circuit's Q, which can all be affected by parastics.
    2. The sensor frequency goes beyond the recommended range given in the data sheet.
    3. The amplitude of the sensor waveform falls beyond the prescribed limits and is either too low or too high. This condition may contribute to saturation indirectly via the resulting distortion & noise from too large or too small a signal.
    4. If the sensor frequency is too high for the reference clock frequency, then the output DATAx could hit its max value (per equation (2)). 
      An example of this condition would be a nominal sensor frequency of 5MHz, and a 2MHz ref clock. 
      The low ref clock could result from a low-frequency master clock or a high value of CHx_FREF_DIVIDER.

    Conditions 1, 2 & 3 should be flagged by the ERR_ALW and/or the ERR_AHW bits in the STATUS register.
    Note, these will in turn be dependent on the ERROR_CONFIG register.

    Condition 4 can be avoided with careful design and identified and by checking for the DATAx value of 2^28. 

    Regards,
    John