S-TouchTM Capacitive Touch Controller PCB Layout Guide 6

Other considerations

Following these basic design guidelines for PCB design and layout can make capacitive sensing applications more reliable. In PCB design, other important factors should also be considered, including:

There are no floating boards/plates on the PCB. The blank area of the PCB can be filled with grounding copper foil or left blank. diode

The PCB should be designed with a required reference capacitance value of less than 20 pF (which is determined during hardware adjustment), and the inherent capacitance of each channel should be less than 10 pF. If it is greater than this value, some basic layouts need to be modified, such as reducing the density of the grounding copper foil, increasing the distance between the sensing input trace/electrode and the grounding copper foil, reducing the width of the sensor signal trace, or even removing the grounding copper foil. If the maximum value of the sensing input capacitor exceeds 10 pF, a tuning capacitor needs to be used for matching settings.

Try to control the difference in inherent capacitance between each sensing channel within 10 pF as much as possible (this difference can be measured during hardware adjustment). If it exceeds 10 pF, it is necessary to reduce the mismatch between trace length and sensor electrode size in order to rearrange and minimize the difference.

Install series resistors in the I2C SDA and SCL circuits to filter out noise interference caused by wiring harnesses connecting the motherboard and touch module, or interference from power supply noise that may cause I2C signal distortion.  diode