AN2869 Datasheet, PDF (1/43 Pages) STMicroelectronics – Guidelines for designing touch sensing applications

AN2869
Application note
Guidelines for designing touch sensing applications
Introduction
This application note describes the layout and mechanical design guidelines used for touch
sensing applications.
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 main difficulty designing such interfaces is to ensure that none of the items 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
Depending on which application you are designing, you may not need to refer to all of the
contents of this document. You can go to the appropriate section after reading the common
part which contains the main capacitive sensing guidelines. For example, if you are
developing an application with only projected electrode, you should first read the main
capacitive sensing guidelines and then go through the sections giving specific
recommendations for projected electrode designs.
Table 1 lists the microcontrollers concerned by this application note.
Table 1. Applicable products
Type
Applicable products
Product family
Proximity and touchkey microcontrollers
STM8A automotive microcontrollers
STM8L ultra-low-power microcontrollers
STM8S mainstream microcontrollers
STM8T touch-sensing microcontrollers
STM32 F0 entry-level Cortex™-M0 microcontrollers
STM32 L1 ultra-low-power ARM Cortex™-M3 based microcontrollers
May 2012
Doc ID 15298 Rev 6
1/43
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