CY8C20xx7/S CapSense
®
Design Guide
Doc. No. 001-78329 Rev. *E
58
6. Liquid-Tolerant Design Considerations
Some CapSense capacitive touch-sensing applications require reliable operation in the presence of water or other
liquids such as ketchup and blood. White goods, automotive applications, and industrial applications are examples of
systems that must perform in environments that include water, ice, humidity changes, or any other liquids. For such
applications, shield electrodes and guard sensors can provide robust touch sensing.
6.1 Shield Electrode and Guard Sensor
Figure 6-1. PCB Layout with Shield Electrode and Guard Sensor
6.1.1 Shield
Shield electrodes protect CapSense button sensors from detecting false touches caused by water drops or liquid
spills. When water drops or any other liquid spills are present on the overlay surface, the coupling between the shield
electrode and sensor pad is increased by C
LD
, as shown in
PCB
Shield Electrode
Guard Sensor
Sensor Pads
