For applications which do not require high sample rates or maximum conversion resolution, the total active conversion time of the FDC can be minimized to reduce power consumption. This can be done by either by using sleep mode or shutdown mode during times in which conversions are not required (see Device Functional Modes).

As an example, for an application which only needs 10 samples per second with a resolution of 16 bits can utilize the low-power modes. The sensor requires SETTLECOUNT = 16 and IDRIVE of 01111b (0.146mA). Given FREF = 40MHz and RCOUNT = 4096 will provide the resolution required. This corresponds to 4096 × 16 × 10 / 40MHz → 16.4ms of active conversion time per second. Start-up time and channel switch delay account for an additional 0.34ms. For the remainder of the time, the device can be in sleep mode: Therefore, the average current is 19.4ms * 3.6mA active current + 980.6ms of 35µA of sleep current, which is approximately 104.6µA of average supply current. Sleep mode retains register settings and therefore requires less I²C writes to wake up the FDC than shutdown mode.

Greater current savings can be realized by use of shutdown mode during inactive periods. In shutdown mode, device configuration is not retained, so the device must be configured for each sample. For this example, configuring each sample takes approximately 1.2ms (13 registers × 92.5 µs per register). The total active time is 20.6ms. The average current is 20ms × 3.6mA active current + 980ms × 2µA of shutdown current, which is approximately 75µA of average supply current.

For further information on power-cycled applications, refer to Power Reduction Techniques for the FDC2214/2212/2114/2112 in Capacitive Sensing Applications.