Touch Screen Chiplet Reference Voltage Sampling
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Solution Overview
Problem
Capacitive touch sensor panels face errors and noise due to parasitic capacitances and interference in reference voltages, which affect the accuracy of touch and proximity sensing in electronic devices.
Innovation Solution
Integrated micro circuitry in touch screens samples low-noise reference voltages and employs frequency response demodulation and signal filtering to minimize interference, using chiplets with voltage sampling circuitry and analog demodulation to adjust frequency response and filter digital data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reference voltages are supplied to micro circuitry in high-resistive supply networks, then the micro circuitry can operate, but noise and interference are picked up by the reference voltages, amplifying noise and introducing errors into touch outputs
Solution Approach 1:
The patent divides the reference voltage supply into multiple separate reference voltages (first reference voltage and second reference voltage) supplied through different high-resistive supply networks. This segmentation isolates noise sources so that interference picked up by one reference voltage does not affect the other, thereby reducing overall noise impact on touch sensing accuracy
Solution Approach 2:
The patent introduces a differential amplifier as an intermediary component that processes the difference between two reference voltages. This differential approach acts as a mediator that rejects common-mode noise and interference while amplifying the useful signal, thereby improving touch sensing accuracy by filtering out noise and interference
2Ease of manufacture
If parasitic or stray capacitances exist between touch node electrodes and other components referenced to chassis ground, then the touch sensor panel can be constructed, but errors and offsets are introduced into touch outputs
Solution Approach 1:
The patent references touch node electrodes to a guard ground that is maintained at the same potential as the touch electrode itself, rather than to chassis ground. This equipotential referencing eliminates voltage differences that would cause parasitic current flow through stray capacitances, thereby preventing errors and offsets in touch outputs while maintaining ease of construction
Solution Approach 2:
The patent introduces a guard ground as an intermediary reference potential between the touch electrodes and chassis ground. This guard ground acts as a mediator that blocks parasitic current paths through stray capacitances while maintaining the electrical integrity of the touch sensing system, thereby improving measurement precision without complicating manufacturing
3Adaptability or versatility
If micro circuitry is integrated into display pixel stack up, then touch sensing can be integrated with display, but interference from supply ripple and bounce is picked up by reference voltages, amplifying noise
Solution Approach 1:
The patent separates the reference voltage supply for touch sensing from the main display power supply by providing dedicated high-resistive supply networks with separate reference voltages. This segmentation isolates the touch sensing reference voltages from supply ripple and bounce generated by display operations, enabling integrated functionality while reducing noise interference
Solution Approach 2:
The patent uses differential amplification as an intermediary mechanism that processes the difference between two reference voltages. This differential approach acts as a mediator that rejects common-mode interference from supply ripple and bounce while preserving the touch sensing signal, thereby enabling integrated touch and display functionality with reduced noise
Data Source
AI summary
An electronic device including a touch screen (e.g., an integrated touch screen using chiplets) can be configured for low-noise reference voltage sampling and subsequent touch sensing using the sampled reference voltage. An integrated touch screen can include multiple regions, and each of the multiple regions can include multiple touch node electrodes. Chiplets can be configured to sample one or more reference voltage pins during an analog quiet time to obtain one or more sampled low-noise reference signals localized to each chiplet. The chiplets can then be configured to sense capacitance at some of or at each of the regions (e.g., using chiplets coupled to some of the touch node electrodes of each of the regions and configured to operate in a touch sensing configuration) using the one or more sampled low-noise reference signals.