Cypress CapSense CY8C20x36 Guía de usuario descargar pdf (Pagina 34)

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

3.1.2 Overlay Thickness

Sensitivity is inversely proportional to overlay thickness, as illustrated in Figure 3-1.

Figure 3-1. Sensitivity vs. Overlay Thickness

Both signal and noise are affected by the overlay properties. Table 3-2 lists the recommended maximum overlay

thicknesses for PSoC CapSense applications with an acrylic overlay material.

Table 3-2. Maximum Overlay Thickness with an Acrylic Overlay Material

Design Element

Max. Overlay Thickness (mm)

Button

Slider

Touchpad

0.5

3.1.3 Overlay Adhesives

Overlay materials must have good mechanical contact with the sensing PCB. This is achieved using a nonconductive

adhesive film. This film increases the sensitivity of the system by eliminating any air gaps between overlay and the

sensor pads. 3M™ makes a high performance acrylic adhesive called 200MP that is widely used in CapSense

applications in the form of adhesive transfer tape (product numbers 467MP and 468MP).

3.2 ESD Protection

Robust ESD tolerance is a natural byproduct of thoughtful system design. By considering how contact discharge will

occur in your end product, particularly in your user interface, it is possible to withstand an 18 kV discharge event

without incurring any damage to the CapSense controller.

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Cypress CapSense CY8C20x36 Guía de usuario Pagina 34