User guide

Getting Started with CapSense Document No. 001-64846 Rev. *A 3
Contents
1. Introduction .................................................................................................................................................................... 6
1.1
How to Use This Guide .......................................................................................................................................... 6
1.2
Cypress CapSense

Products ............................................................................................................................... 6
1.2.1
Cypress CapSense Differentiation ............................................................................................................ 6
1.3 Document Revision History ................................................................................................................................... 7
1.4
Document Conventions ......................................................................................................................................... 7
2. CapSense Technology .................................................................................................................................................. 8
2.1
Capacitive Sensing Methods ................................................................................................................................. 8
2.1.1 Self Capacitance ....................................................................................................................................... 8
2.1.2
Mutual Capacitance .................................................................................................................................. 9
2.2 Self-Capacitance Equivalent Model ....................................................................................................................... 9
2.3
CapSense Sensing Technology .......................................................................................................................... 10
2.3.1
Sensing Methods .................................................................................................................................... 10
2.3.2
Capacitance Conversion ......................................................................................................................... 10
2.3.3 CapSense with Sigma Delta Modulator (CSD) ....................................................................................... 11
2.3.4
CapSense Successive Approximation Electromagnetic Compatible (CSA_EMC) .................................. 12
2.4 CapSense Tuning ................................................................................................................................................ 13
2.4.1
Signal-to-Noise Ratio (SNR) ................................................................................................................... 14
2.4.2 SmartSense™ Auto-Tuning .................................................................................................................... 14
2.5
Sensor Types ...................................................................................................................................................... 15
2.5.1 Buttons (Zero-dimensional Sensors) ...................................................................................................... 15
2.5.2
Sliders (One-dimensional Sensors) ........................................................................................................ 16
2.5.3 Touchscreens and Trackpads (Two-Dimensional Sensors) ................................................................... 18
2.5.4
Proximity (Three-dimensional Sensors) .................................................................................................. 18
2.6 Sensor Construction ............................................................................................................................................ 19
2.6.1
Field Coupled via Copper Trace (PCB) .................................................................................................. 19
2.6.2 Field Coupled via Spring/Gasket/Foam .................................................................................................. 19
2.6.3 Field Coupled via Printed Ink .................................................................................................................. 20
2.6.4
Field Coupled via ITO Film on Glass ...................................................................................................... 20
2.7 CapSense Feedback ........................................................................................................................................... 20
2.7.1
Visual Feedback ..................................................................................................................................... 20
2.7.2 Haptic Feedback ..................................................................................................................................... 24
2.7.3
Audible Feedback ................................................................................................................................... 24
2.8 CapSense System Overview ............................................................................................................................... 27
2.8.1
Hardware Component ............................................................................................................................. 27
2.8.2 Firmware Component ............................................................................................................................. 27