Hardware design guide
KE15Z Touch Sensing Interface, User's Guide, Rev. 0, 12/2016
NXP Semiconductors
21
Annual gap size
4.4. Electrodes placement
The following are recommendations for placing the touch sensing electrodes on a PCB or FlexPCB.
•
All touch electrodes should be placed as close to the MCU as possible. As the long trace loops in
layout causes extra intrinsic capacitance and easily coupled noise, placing touch electrodes closer
to the chip is always better.
•
Components underneath electrodes — It is not recommended to place any component underneath
the touch sensing electrode's area, especially in two layer boards.
•
Keep electrodes far away power module, RF antenna, etc.
4.5. Hardware checklist
The following is a checklist based on the recommendations in this application note. Before having a
board, film, ITO, and the touch sensing board made, make sure the design follows all or most of these
rules:
•
GND return path is provided per specifications (GND hatch below or at least around the
electrode keypad).
•
No pull-ups present in TSI-enabled (touch sensing input module) pins.
