S-Touch devices: system considerations

This application note discusses some of the system-level factors that can influence the touch detection of capacitive touch sensors. The various size, shape and materials used in sensors pose a challenge to the design of a reliable touch device. The environmental effects (temperature, humidity, EMI) also influence the sensor's performance.

Using a finite state machine approach, the S-Touch capacitive touch sensors are totally hard-wired and thus able to provide highly optimized performance. The S-Touch devices are able to provide stable and reliable touch detection by compensating for environmental variations using an internal automatic calibration mechanism. The effect of external factors like noise and water film can be filtered out by appropriate setting of the touch variance (TVR), environmental variance (EVR), and integration time and strength threshold registers as explained in this application note.

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