Datasheet

CY8C21x34/B CapSense
®
Design Guide Document No. 001-66271 Rev. *B 43
6. Water Tolerance
Some CapSense capacitive touch-sensing applications require reliable operation in the presence of water. White
goods, automotive applications, and industrial applications are examples of systems that must perform in
environments that include water, ice, and humidity changes. 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. When water
drops are present on the overlay surface, the coupling between the shield electrode and sensor pad is increased by
C
WD
, as shown in Figure 6-2.
PCB
Shield Electrode
Guard Sensor
Sensor Pads