Sensitivity; Table 5. Sensitivity Documentation; Table 6. Dielectric Constants Of Common Materials Used In A Panel Construction - ST STM32F0 Series Application Note

5.4

Sensitivity

Sensitivity is a key point in touch sensing applications. The sensitivity can be improved by:
• Reduce air gap
• Reduce panel thickness
• Choose dielectric with higher ε
• GND plane must not too close from shield and sensors
• Avoid metallic paint near shield and sensors

Table 5. Sensitivity documentation

Id
AN1913
AN4312
AN4316
Dielectric example
Polyethylene terephthalate (PET)
PMMA (Poly methyl methacrylate)
AN5105 - Rev 1
R
gives a list of documents containing information about the sensitivity.
Table 5.
Title
Developing applications on STM32Cube with
STMTouch® touch sensing library
Guidelines for designing touch sensing applications
with surface sensors
Tuning a STMTouch-based application
Table 6. Dielectric constants of common materials used in a panel construction
Material
Air
Glass
Sapphire glass
Mica
Nylon
Plexiglass
Polyethylene
Polystyrene
FR4 (fiberglass + epoxy
Typical PSA
Sensitivity documentation
GPIO mode (table)
Air Gap:
• Reduce air gap
Changing the Panel material:
• Reduce Panel thickness
• Choose dielectric with higher ε
Metal chassis:
• GND not too closed from Shield and Sensors
• Avoid Metallic paint near Shield and Sensors
Mechanical construction and PCB to panel bonding.
Surface sensor design
All chapter
2.0 - 3.0 (approximately)
AN5105
Sensitivity
Chapter
R
ε
R
1.00059
4 to 10
9 to 11
4 to 8
3
3.4
2.2
2.56
3.7
4.2
2.6 to 4
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