AN3431 Datasheet, PDF (1/18 Pages) STMicroelectronics – How to design a PresSense pressure touch button

AN3431
Application note
How to design a PresSense pressure touch button
Introduction
Traditional capacitive touch sensing solutions offer several advantages such as reduced
cost and no mechanical moving parts. The simple mechanical design of capacitive touch
sensing systems facilitates sealing water off devices while simultaneously maintaining a
very professionnal look and feel. There are however, some limitations. Such limitations can
be addressed by capacitive sensing technology but, in a different form called press to sense
technology (PresSense).
The advantages of PresSense over traditional capacitive sensing implementations are as
follows:
■ Water does not affect the measurements of PresSense capacitive sensing devices
whereas traditional capacitive sensing devices, with sensors that may be susceptible to
water/other contaminants, must follow special design considerations.
■ PresSense capacitive sensing devices present no problems for users with gloves.
■ PresSense capacitive sensing devices can have a metallic finish whereas traditional
capacitive sensing devices cannot.
■ PresSense capacitive sensing devices have a higher radio frequence (RF) immunity.
■ False detections are significantly reduced in PresSense capacitive sensing devices as a
small force is required for an actuation.
This application note describes how to design a PresSense touch sensing solution using
electrodes and a metal layer.
Typical applications that are best suited for the PresSense series include:
■ Stoves
■ Waterproof housing
■ Microwave ovens
■ Industrial applications
■ Kitchen appliances
■ Waterproof keypads
September 2011
Doc ID 019017 Rev 1
1/18
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