AN0040: Hardware Design for Capacitive Touch with EFM32 Microcontrollers
Application note detailing hardware design for capacitive touch sensing using EFM32 microcontrollers, covering sensor layout, SNR optimization, and low-energy implementation.
Overview
This application note (AN0040) provides comprehensive hardware design guidelines for implementing capacitive touch sensing with Silicon Labs EFM32 microcontrollers. It explains the principles of self-capacitance sensing using an internal analog comparator to create an RC relaxation oscillator. The document details design specifications for touch buttons and sliders, including optimal pad dimensions (10mm to 20mm), shapes, and spacing requirements to maintain a signal-to-noise ratio (SNR) above 5. It specifically highlights the use of the Low Energy Sensor Interface (LESENSE) for achieving ultra-low power consumption and 'wake on touch' functionality. Additionally, the note addresses environmental disturbances and PCB layout techniques to minimize interference and improve sensor reliability.
Use Cases
- Low-power human-machine interface (HMI) design
- Battery-powered 'wake on touch' device implementation
- PCB layout optimization for capacitive sensor performance
- Consumer electronics button and slider design
Topics
Referenced Parts
EFM32
Silicon Laboratories
hardware design for capacitive touch sensing with the EFM32 microcontrollers