AN4312 Datasheet, PDF (1/36 Pages) STMicroelectronics – Guidelines for designing touch sensing applications with surface sensors

AN4312
Application note
Guidelines for designing touch sensing applications
with surface sensors
Introduction
This application note describes the layout and mechanical design guidelines used for touch
sensing applications with surface sensors.
Capacitive sensing interfaces provide many advantages compared to mechanical user
interfaces. They:
• offer a modern look and feel
• are easy to clean
• are waterproof
• are robust
Capacitive sensing interfaces are more and more used in a wide range of applications. The
interface is based on surface sensors that are made of small copper foils. The sensor acts
as a capacitor that is alternatively charged and discharged. The capacitor value depends on
the presence of the user finger as well as the sensor design. This application note
introduces various sensor designs and recommendations to achieve optimum
performances, keeping in mind that none of the sensor elements should interfere with each
other.
This document provides simple guidelines covering three main aspects:
1. Printed circuit board (PCB)
2. Overlay and panel materials
3. All other items in the capacitive sensor environment
Table 1 lists the microcontrollers concerned by this application note.
Type
Microcontrollers
Table 1. Applicable products
Applicable products
STM32F0 series, STM32F3 series, STM32L1 series, STM8L series.
September 2013
DocID024815 Rev 1
1/36
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