User guide

Getting Started with CapSense Document No. 001-64846 Rev. *A 49
3.7.4 Button Design
The best shape for buttons is round. Rectangular shapes with rounded corners are also acceptable. Sharp points
concentrate fields, so avoid sharp corners (less than 90º) when designing your sensor pad.
Figure 3-27. Recommended Button Shapes
Button diameter can range from 5 mm to 15 mm, with 10 mm being suitable for the majority of applications. A larger
diameter helps with thicker overlays.
Annular gap size should be equal to the overlay thickness, but no smaller than 0.5 mm, and no larger than 2 mm. For
example, a PCB layout for a system with a 1-mm overlay should have a 1-mm annular gap, while a 3-mm overlay
design should have a 2-mm annular gap. The spacing between the two adjacent buttons should be large enough that
if one button is pressed, a finger should not reach the annular gap of the other button.
3.7.5 Slider Design
A typical slider pattern is shown in Figure 3-28. The recommended dimensions for slider design are given in
Table 3-4.
Figure 3-28. Typical Slider Pattern
Table 3-4. Slider Dimensions
Parameter Min Max Recommended
Width of the Segment (A) 2 mm 7 mm Equal to overlay thickness, but within the min/max limits.
Clearance between Segments ( B ) 0.5 mm 2 mm Equal to sensor to ground clearance
Height of the segment ( C ) 7 mm 15 mm 12 mm