Cypress CapSense CY8C20x36 Guia do Utilizador descarregar pdf (Página 56)

56 Document No. 001-64846 Rev. *I Getting Started with CapSense

 Slow the edges of the shield waveform

 Reduce the slew rate of shield electrode by adding a filter capacitor between the shield electrode port pin

and ground.

Guard Sensor:

The guard sensor is a copper trace that surrounds all of the buttons, as shown in Figure 3-39.

Figure 3-39. PCB Layout with Shield Electrode and Guard Sensor

PCB

Shield Electrode

Guard Sensor

Sensor Pads

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

than 1 cm from these features.

 The recommended shape for a guard sensor is rectangular with curved edges.

 Recommended thickness of copper trace is 2 mm and distance of Copper trace to shield hash is 1 mm. This is a

general recommendation and will vary based on the design.

You can also refer to the individual device design guides webpage for sample layouts of all the CapSense devices:

 CY8C21x34 design guide

 CY8C20x34 design guide

 CY8C20xx6A design guide

3.7.13 CapSense System Design with Single Layer PCB

Electronic product manufacturers face constant pressure to lower system costs. Several markets, including consumer

and home appliances, are switching to single layer PCBs to support their required product margins. Cypress‘s

CapSense controllers provide robust touch sensing on single layer PCBs, and their driven shield capability enables

longer trace length, proximity sensing, and water tolerance. CapSense delivers IEC (IEC 61000-6-1, IEC 61000-6-2)

noise compliant performance for accurate touch responses even in noisy environments using sophisticated firmware

algorithms. For more details on implementing CapSense touch sensing on single layer boards, contact

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Cypress CapSense CY8C20x36 Guia do Utilizador Página 56