FDC1004: Effective resolution and frequency response

Hello, 

We do not have available data for the resolution at 400S/s but the effective resolution can be determined by taking a ratio of the full scale range to RMS measurement noise. This will vary per application but in general, faster sample rates will result in less resolution. 

As for the frequency response questions, the FDC1004 does measure the actual capacitance using an excitation along with a sample and hold setup. See below: 

You can find more information on this in the FDC1004: Basics of capacitive sensing and applications app note. 

As for the frequency response graphs, I will need to check with a colleague on that once they are back next week and will give you an answer then. 

Lastly, frequency has a couple different uses on the FDC1004: the clock frequency, the excitation frequency, and the sample rate which is sometimes referred to as a frequency. 

Best Regards, 

Hello,

The excitation is based on a 25 khz clock. The ADC does not measure the excitation frequency and measures the capacitance and hence called capacitance to digital converter. The excitation frequency is the frequency to the sensor and the ADC converts the measured capacitance to digital output. The frequency response graph indicates the throughput response of a capacitance measurement at different sample rates. So it should be viewed as how fast the capacitance changes with respect to change in capacitance measurement.