Single-Pin Self-Capacitance Sensing With Internal Reference Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing touch sensor testing methods rely heavily on external components and complex configurations, making them inefficient and prone to false readings due to noise and interference, particularly when assessing capacitive sensors in devices like touchscreens and keyboards.
Innovation Solution
A simplified test configuration using internal capacitive sensor structures, including an Analog to Digital Converter (ADC), multiplexor (MUX) switches, and a reference capacitor, which measures capacitance changes without external sampling capacitors, reducing reliance on external circuitry and enhancing noise rejection through burst switching and differential voltage measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sampling capacitors and complex test configurations are used, then capacitance measurement capability is improved, but device complexity and susceptibility to noise increase
Solution Approach 1:
The capacitive sensor device measures its own self-capacitance using its internal resources (ADC, MUX switches, reference capacitor) without requiring external sampling capacitors or complex test equipment. The device serves itself by utilizing its existing circuitry for self-diagnosis and characterization.
Solution Approach 2:
The internal circuitry of the capacitive sensor device (ADC, MUX switches, reference capacitor) is designed to serve multiple functions: normal sensor operation and self-capacitance measurement. This multi-functionality eliminates the need for separate external testing components.
2Measurement precision
If external components are used for testing, then measurement capability is improved, but reliability decreases due to noise and interference
Solution Approach 1:
The invention extracts the measurement function from external components and relocates it entirely within the device under test. By removing external sampling capacitors and test equipment from the measurement path, the source of noise and interference is eliminated, improving reliability.
Solution Approach 2:
The internal reference capacitor serves as an intermediary element that enables self-capacitance measurement without requiring external components. This internal mediator provides a stable reference for comparison while remaining isolated from external noise sources.
3Device complexity
If simplified internal test configurations are used, then device complexity is reduced, but measurement precision may worsen
Solution Approach 1:
The invention merges the test configuration with the operational circuitry of the capacitive sensor device. By combining measurement functions with existing internal components (ADC, MUX, reference capacitor), the system achieves simplified testing without sacrificing measurement precision that would normally require complex external setups.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate and efficient capacitance measurement within touch sensor devices, reducing false readings and noise interference, thereby improving the reliability of touch detection in capacitive sensors without the need for additional external components.
Implementation Method 1
a capacitive sensor device having a driving layer and a sensing layer... touch to the surface changes electrical relationships within the touch sensors
Data Source
AI summary
A method for measuring capacitance in a sensor device using an internal reference circuit element(s), and without implementing additional circuitry and devices external to the sensor device, is described. In some embodiments a method uses an output pin of the sensor device and an internal reference capacitor of the sensor device to identify a touch applied to a touch point or electrode coupled to the touch sensor. The method applies reference voltages to charge the reference capacitor and measure a signal received from an electrode, wherein the touch sensor controls switching within the touch sensor to apply the reference voltages to the reference capacitor.