Proposed functions allow performing run-time sensors diagnostic in CSD-based designs. These functions can detect sensor lines shorts to Vcc or ground, sensor-to-sensor shorts and modulator components faults. Also sensor pads disconnection could be detected.

One of the main development goals for capacitive sensing applications is reliability enhancement for devices with capacitive sensors in harsh or sensitive environemnts. Improvements in front panel reliability are achieved through several different methods. New capacitive sensing methods such as the sigma-delta modulator (CSD) and successive approximation (CSA), both offered as user modules (UMs) in PSoC signal-to-noise ratio (SNR), EMI and ESD immunity and immunity to power supply and input transients. Considerable efforts are also made to eliminate improper operation modes in software. Such software tricks include application programming interfaces (APIs) that employ of different positive/negative noise thresholds and debounce counters.

The included application note demonstrates how to use the unique PSoC hardware reconfiguration possibilities to detect errors in capacitive sensing measurement in runtime. Such errors include: shorts to VDD or ground, sensor-to-sensor shorts, sensor disconnects and faults of sigma-delta modulator external components such as modulation capacitor Cmod and a discharge resistor Rb. Such diagnostics should be used to provide fail-safe function of capacitive sensing devices in cases when sensor faults lead to safety concerns. White goods, automotive and industrial electronic applications could be mentioned as examples of devices that require sensors fault diagnostic for safe operations.

Proposed FMEA implementation is based on International Standard IEC60335. Proposed diagnostic functionality could be added to existing CapSense projects by adding several FMEA function calls.