The FDC supports two sensor configurations. Both configurations use an LC tank to set the frequency of oscillation. A typical choice is an 18-μH shielded SMD inductor in parallel with a 33pF capacitor, which result in a 6.5MHz oscillation frequency. In the single-ended configuration in Figure 7-1, a conductive plate is connected IN0A. Together with a target object, the conductive plate forms a variable capacitor.

Figure 7-1 Single-Ended Sensor Configuration

In the differential sensor configuration in Figure 7-2, one conductive plate is connected to IN0A, and a second conductive plate is connected to IN0B. Together, they form a variable capacitor. When using an single-ended sensor configuration, set CHx_FIN_SEL to b10 (divide by 2).

Figure 7-2 Differential Sensor Configuration

The single-ended configuration allows higher sensing range than the differential configuration for a given total sensor plate area. In applications in which high sensitivity at close proximity is desired, the differential configuration performs better than the single-ended configuration.