Mutual-Capacitance Touch Sensing with Reconfigurable CSD Circuitry
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Solution Overview
Problem
Capacitance-sensing systems face challenges in accurately detecting touch locations and multi-finger touch support with high accuracy, particularly in cost-effective and efficient mutual-capacitance sensing solutions for touch panels.
Innovation Solution
The implementation of a self-capacitance device (CSD) component configured for mutual capacitance sensing, utilizing a processing device with an input node, transmit signal generation circuit, logic circuitry, and analog-to-digital converter to measure mutual capacitance between electrodes, allowing for concurrent use of any capacitance sensing pin for transmit or receive signals, and employing off-chip or on-chip capacitors for mutual and self-capacitance sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mutual capacitance sensing is implemented using conventional circuits, then multi-finger touch support is achieved, but device complexity and cost increase
Solution Approach 1:
The self-capacitance sensing device is configured to perform both self-capacitance sensing and mutual capacitance sensing functions using the same hardware circuitry. The device can operate in different sensing modes (self-capacitance mode and mutual capacitance mode) by reconfiguring the existing capacitive sensing circuit, eliminating the need for separate dedicated circuits for each sensing type and reducing overall device complexity while maintaining multi-finger touch support capability
2Ease of manufacture
If self-capacitance sensing device is used for mutual capacitance sensing, then cost is reduced, but measurement precision may be affected
Solution Approach 1:
The system dynamically switches between self-capacitance sensing mode and mutual capacitance sensing mode based on the touch detection requirements. During the sensing process, the device alternates between measuring self-capacitance values and mutual capacitance values using the same hardware circuit, allowing cost-effective implementation while maintaining measurement precision through adaptive mode switching and signal processing techniques
3Measurement precision
If conventional mutual capacitance sensing circuits are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The self-capacitance sensing device is designed with universal circuitry that can perform both self-capacitance measurements and mutual capacitance measurements. By reconfiguring the existing capacitive sensing circuit to operate in different modes, the device achieves touch location accuracy comparable to dedicated mutual capacitance circuits while avoiding the need for complex separate circuitry, thus reducing device complexity without sacrificing measurement precision
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
Enables precise detection and tracking of touch objects and styluses on capacitive sense arrays, supporting multi-finger touch and higher accuracy in finger movement detection, while providing a cost-effective solution for mutual-capacitance sensing applications.
Implementation Method 1
measure a mutual capacitance between a first electrode and a second electrode... mutual capacitance where the capacitance-sensing circuit has access to both electrodes of the capacitor
Data Source
AI summary
Apparatuses and methods of mutual-capacitance sensing with a capacitance-sensing circuit, such as a self-capacitance sensing device (CSD). One apparatus includes an input node coupled to a capacitance sense pin to couple to a first electrode of a sense array, a transmit (TX) signal generation circuit to generate a TX signal to drive a second electrode of the sense array, logic circuitry coupled to the TX signal generation circuit and the input node. The logic circuitry is configured to selectively couple a first capacitor to the input node and a second capacitor to the input node timed with the TX signal. The apparatus further includes an analog-to-digital converter (ADC) coupled to receive a receive (RX) signal from the input node and to convert the RX signal into a digital value, the digital value representing a mutual capacitance between the first electrode and the second electrode.