FDC2214: Target distance vs resolution of device (FDC22xx, FDC21xx)

Hello,

Your understanding is correct. If the sensor, components, and all other system level factors are the same then changing the sample rate / RCOUNT will change how much noise is filtered by the device which can be correlated to a distance precision.

The question about the graphs requires an understanding of signal-to-noise ratio.

Figures 59-61 have a y-axis that shows capacitance change which is information about the signal change for a given sensor, so it will be the same for the FDC211x and FDC221x.

Figure 62 has a y-axis that is distance precision which requires the following information to plot:

• Capacitance change at each distance to create a curve fit between capacitance and distance (device independent): Provided by figures 59-61
• Peak-to-peak noise level at each distance (device dependent): Not shown

Once this information is gathered you can show precision by converting peak-to-peak noise at each distance to how many millimeters peak-to-peak it represents which is effectively the precision of the sensor at that distance. Since the noise level of the FDC211x is truncated to 12 bits (+4 bits of gain if used) this plot will look different for both devices. In this case figure 62 is showing the FDC221x, sorry that this information is not mentioned.

Regards,

Luke