3 Layout Guidelines

This section provides a general layout guidelines for touch applications. For application-specific information, please refer to the relevant topics or contact the Microchip Technical Support team.

Below are the recommended guidelines for touch sensor PCB layout.

Sensor Placement and Routing
  • Maintain a minimum clearance of 3 mm between sensors.
  • Place the series resistor for the sensor pin as close as possible to the MCU pin.
  • Minimize the sensor line track width in accordance with PCB DFM guidelines.
  • For applications with reduced front panel thickness, the sensor track may be routed on the opposite side of the touch sensor.
  • Minimize the use of vias on the sensor track.
Reference Layer Recommendations
  • In 2-layer or multilayer designs, avoid referencing the sensor track to GND.
  • Maintain a minimum PCB stack-up clearance of 1 mm between the sensor track and GND or Two-Level Driven Shield layers
  • For Three-Level Driven Shield layers, the PCB stack-up clearance may be less than 1 mm.
  • GND or Two-Level Driven Shield layers can be implemented as a hatched pattern with a fill percentage between 25% and 50%.
Spacing Clearance for sensor traces

Below is the recommended practice: If additional routing space is available, increase the clearance wherever possible.

  • Maintain a minimum track clearance between sensor line tracks equal to 1x the track width. If additional routing space is available, increase the clearance wherever possible
  • Maintain a minimum track clearance between the sensor and other tracks of at least 2x the trace width.
  • Maintain a minimum track clearance of 1 mm between the sensor and GND/Two-Level Driven Shield.
  • Maintain a minimum track clearance of 0.2 mm between the sensor and Three-Level Driven Shield.
Flex PCBs

The above guidelines also apply to flex PCB.

Reference layer shielding using GND or Two-Level Driven Shield is not recommended. It is recommended to use a coplanar shield, and for reference layer shielding, use a Three- Level Driven Shield.

The provided guidelines serve as a starting point for optimizing touch sensor performance and reliability in your PCB design.