AN376: Effects of ESD Protection Devices on Capacitive Sensing Performance

Silicon Laboratories' capacitive sensing techniques are compatible with external ESD protection methods. Designers should be aware of parasitic parameters in these circuits which affect capacitive sensing performance when implementing these protection methods. While most of the methods affect sensing performance in some way, in almost all cases an acceptable balance between performance, protection, and cost is easily achievable. This application note describes several typical ESD protection techniques, their mode of operation, and the effects of commonly-introduced parasitic parameters on the different methods of capacitive sensing provided by Silicon Laboratories including charge rate measurement/relaxation oscillator (RO) methods and direct capacitive measurement (C2D).