Hardware design guide
KE15Z Touch Sensing Interface, User's Guide, Rev. 0, 12/2016
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NXP Semiconductors
4.3. Ground plane
A ground plane prevents coupling of external electromagnetic interference to the touch sensing
electrodes, and acts as a shield for undesired electric fields. However, abusing the ground planes or
simply filling open areas with ground planes might affect the sensor's sensitivity.
Following are a few recommendations and best practices for ground planes usage.
Use X-hatch pattern on the top layer, 25% ground fill, 7mil line, 45mil spacing.
Use X-hatch pattern on the bottom layer (e.g. underneath the electrodes area), 17% ground fill,
7mil line, 70mil spacing.
Ground plane
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.
