Cypress CapSense CY8CMBR2044, Design Manual

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AN66308 - CY8CMBR2044 CapSense® Design Guide, Doc. No. 001-66308 Rev. *F 3
Contents
1. Introduction .................................................................................................................................................................... 5
1.1 Abstract ................................................................................................................................................................. 5
1.2
Cypress’s CapSense Documentation Ecosystem .................................................................................................. 5
1.3 CY8CMBR2044 CapSense Express
™ Device Features ....................................................................................... 7
1.4 Document Conventions ......................................................................................................................................... 9
2. CapSense Technology ................................................................................................................................................ 10
2.1 CapSense Fundamentals .................................................................................................................................... 10
2.2 Capacitive Sensing Method ................................................................................................................................. 11
2.2.1 CapSense Sigma-Delta (CSD) ............................................................................................................... 11
2.3 SmartSense Auto-Tuning .................................................................................................................................... 13
2.3.1 Process Variation.................................................................................................................................... 13
2.3.2 Reduced Design Cycle Time .................................................................................................................. 13
3. CapSense Schematic Design ..................................................................................................................................... 15
3.1 CY8CMBR2044 Configuration Options ............................................................................................................... 15
3.1.1 CapSense Buttons (CSx) ........................................................................................................................ 15
3.1.2 General-Purpose Outputs (GPOx) .......................................................................................................... 15
3.1.3 Modulation Capacitor (C
MOD
) .................................................................................................................. 15
3.1.4 Button Auto Reset (ARST) ...................................................................................................................... 16
3.1.5 Toggle ON/OFF ...................................................................................................................................... 16
3.1.6 Flanking Sensor Suppression (FSS) ....................................................................................................... 17
3.1.7 LED ON Time ......................................................................................................................................... 18
3.1.8 System Diagnostics ................................................................................................................................ 19
3.1.9 Scan Rate/Sleep ..................................................................................................................................... 21
3.1.10 Serial Debug Data Out ............................................................................................................................ 22
3.2 Design Toolbox .................................................................................................................................................... 25
3.2.1 General Layout Guidelines ..................................................................................................................... 25
3.2.2 Layout Estimator ..................................................................................................................................... 26
3.2.3 C
P
, Power Consumption and Response Time Calculator ....................................................................... 27
3.2.4 Design Validation .................................................................................................................................... 28
4. Electrical and Mechanical Design Considerations ................................................................................................... 30
4.1 Overlay Selection ................................................................................................................................................ 30
4.1.1 Bonding Overlay to PCB ......................................................................................................................... 31