Cypress CapSense CY8C20x36 Guía de usuario descargar pdf (Pagina 55)

Getting Started with CapSense

Document No. 001-64846 Rev. *I 55

Figure 3-37. Recommended Button and Slider Layout Bottom Layer

3.7.12 Shield Electrode and Guard Sensor

Shield:

 Shield-electrode copper-hatch recommendations

 Top layer – 7-mil trace and 45-mil grid (15 percent fill)

 Bottom layer – 7-mil trace and 70-mil grid (10 percent fill)

 Only areas surrounding sensor pads and the CapSense controller should be grounded

 Reduce the size of the shield patterns

 The shield electrode pattern should surround the sensor pad and exposed traces, and spread no further

than 1 cm from these features. Spreading the shield electrode beyond 1 cm has negligible effect on system

performance. If board space is limited, the shield can spread less than 1 cm. In Figure 3-38, Sensor-1 shows

an example of a shield pattern surrounding a sensor pad and trace routed on the top layer. Sensor-2 shows

an example of a shield pattern with a sensor pad without a trace on the top layer.

Figure 3-38. Shield Electrode Pattern

1 cm

Sensor-1

Sensor-2

PCB – Top Layer

Shield Electrode

Plane

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Cypress CapSense CY8C20x36 Guía de usuario Pagina 55