Proximity sensing is a key feature in many smart applications. This feature is used for system wake-up, collision avoidance, and gesture recognition. Capacitive sensing solutions are typically implemented to achieve simple yet robust proximity detection. This application note reviews important system considerations when designing with Texas Instruments' resonator-based capacitive sensing chips, the FDC2x1y family. Guidelines for sensor system design and grounding techniques are provided through mathematical modeling and qualitative assessment of external parasitic capacitance.