Hybrid Touch Sensing Architecture for Small Form Factors
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Solution Overview
Problem
Small form factor devices face challenges in integrating touch sensing due to limited space for touch sensor panels and the number of I/O channels required, leading to difficulties in detecting touches, especially with poorly grounded objects, which result in negative pixel effects and reduced signal levels.
Innovation Solution
A touch sensing architecture that includes a touch controller with a smaller footprint and fewer I/O channels, utilizing discrete column electrodes and continuous row electrodes to minimize the impact of negative pixels and increase signal amplitude, while supporting multi-touch capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixelated self-capacitance architecture is used to provide high-resolution touch detection, then touch detection precision is improved, but the number of I/O channels required increases significantly
Solution Approach 1:
The touch sensor panel is divided into multiple zones with different sensing architectures. First zones use mutual capacitance sensing with discrete electrodes for accurate single-touch detection, while second zones use projected capacitance sensing with continuous electrodes for multi-touch detection. This segmentation allows each zone to use the most appropriate architecture for its intended function, reducing overall I/O channel requirements while maintaining high detection precision where needed.
Solution Approach 2:
The patent transitions from a uniform 2D matrix of discrete electrodes to a hybrid architecture that incorporates continuous electrodes extending across the panel. This dimensional change allows continuous sensing lines to replace multiple discrete electrode connections, significantly reducing the number of I/O channels required while maintaining touch detection capability across the entire panel surface.
2Adaptability or versatility
If mutual capacitance sensing is used to detect touches, then multi-touch capability is improved, but negative pixel effects increase when objects are poorly grounded
Solution Approach 1:
Different sensing architectures are assigned to different zones based on local requirements. First zones with discrete electrodes use mutual capacitance sensing optimized for single-touch detection where high precision is needed, while second zones with continuous electrodes use projected capacitance sensing optimized for multi-touch detection. This local optimization ensures each zone has the quality characteristics needed for its specific function, reducing negative pixel effects in single-touch scenarios while maintaining multi-touch capability.
3Volume of moving object
If the number of I/O channels is reduced to fit small form factor devices, then device size is improved, but touch sensing capability is degraded
Solution Approach 1:
The touch panel is segmented into zones with different electrode configurations and sensing architectures. Continuous electrodes in second zones replace multiple discrete electrode connections, significantly reducing I/O channel requirements. This allows small form factor devices to implement touch sensing with fewer I/O channels while maintaining adequate touch sensing capability through the hybrid architecture.
Solution Approach 2:
The continuous electrodes serve multiple functions: they act as sensing elements for projected capacitance measurement, provide structural support for the touch panel, and reduce the need for additional discrete connection elements. This multi-functionality allows the system to maintain touch sensing capability while reducing overall component count and I/O channel requirements.
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
The solution enables effective touch detection in small form factor devices with reduced I/O channels, minimizing negative pixel effects and enhancing signal amplitude, even with poorly grounded touches, thus improving the reliability of touch sensing.
Implementation Method 1
Capacitive touch sensor panels can detect a touch, or a near-touch, of a proximate object by detecting the effect of capacitive coupling between the object and the touch electrodes
Implementation Method 2
Self-capacitance touch sensing is based on detecting a change in the self-capacitance between an electrode and ground
Implementation Method 3
Mutual capacitance touch sensing is based on detecting a change in the mutual capacitance between a drive electrode and a sense electrode
Implementation Method 4
When a proximate object is well-grounded, charge can be coupled to ground through the object. In the case of mutual capacitance touch sensing, this coupling of charge to ground reduces the mutual capacitance between the drive electrode and the sense electrode
Data Source
AI summary
A touch sensor panel operable within small form factor devices utilizes a plurality of discrete column electrodes arranged in a plurality of columns, and a plurality of continuous row electrodes arranged in a plurality of rows. Each column is divided into a plurality of regions, with each region formed from a plurality of electrically connected discrete column electrodes within that column. A scan plan includes a series of mutual capacitance scans wherein discrete column electrode(s) in all regions in all columns are sequentially stimulated, and AC signals indicative of mutual capacitance at certain the continuous row electrode(s) is measured. The scan plan includes a series of projection self-capacitance scans, wherein AC signals indicative of self-capacitance at a plurality of continuous row electrodes is measured for all rows, and AC signals indicative of self-capacitance at the discrete column electrodes in each region of all columns is measured.