SNOA961A
February 2017 – February 2023
LDC2112
,
LDC2114
,
LDC3114
,
LDC3114-Q1
Inductive Touch System Design Guide for HMI Button Applications
1
Mechanical Design
1.1
Theory of Operation
1.2
Button Construction
1.3
Mechanical Deflection
1.4
Mechanical Factors that Affect Sensitivity
1.4.1
Target Material Selection
1.4.1.1
Material Stiffness
1.4.1.2
Material Conductivity
1.4.2
Button Geometry
1.4.3
Spacing Between Target and Sensor
1.5
Layer Stacks of Touch Buttons
1.5.1
Conductive Surface
1.5.2
Non-Conductive Surface
1.6
Sensor Mounting Reference
1.7
Sensor Mounting Techniques
1.7.1
Adhesive-Based
1.7.2
Spring-Based
1.7.3
Slot-Based
1.8
Mechanical Isolation
2
Sensor Design
2.1
Overview
2.1.1
Sensor Electrical Parameters
2.1.2
Sensor Frequency
2.1.3
Sensor RP and RS
2.1.4
Sensor Inductance
2.1.5
Sensor Capacitance
2.1.6
Sensor Quality Factor
2.2
Inductive Touch
2.3
LDC211x/LDC3114 Design Boundary Conditions
2.4
Sensor Physical Construction
2.4.1
Sensor Physical Size
2.4.2
Sensor Capacitor Position
2.4.3
Shielding INn traces
2.4.4
Shielding Capacitance
2.4.5
CCOM Sizing
2.4.6
Multi-Layer Design
2.4.6.1
Sensor Parasitic Capacitance
2.4.7
Sensor Spacers
2.4.8
Sensor Stiffener
2.4.9
Racetrack Inductor Shape
2.5
Example Sensor
3
Summary
4
Revision History
2.4
Sensor Physical Construction