Touch Sensor Noise Measurement Circuit and Multiplexer
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Solution Overview
Problem
Existing touch screen technologies face challenges in accurately measuring noise across the entire screen, as current methods can only measure noise at predetermined positions, limiting the improvement of signal-to-noise ratio (SNR) and sensitivity.
Innovation Solution
A method and circuit for driving touch sensors that involve connecting sensor lines to a sensing unit at multiple noise measurement frequencies, using a multiplexer to simultaneously connect multiple channels during noise measurement, and adjusting amplification and integration parameters to enhance noise measurement accuracy and range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If noise measurement is performed at a particular position only, then measurement process is simple, but measurement precision is insufficient because noise cannot be measured at other positions
Solution Approach 1:
The touch screen is divided into multiple measurement regions, with sensor lines grouped into different channels that can be independently measured. The sensing unit sequentially connects to different groups of sensor lines through the multiplexer, enabling noise measurement at multiple positions across the entire touch screen rather than at a single location.
Solution Approach 2:
The sensing unit is designed to handle multiple measurement functions by sequentially connecting to different channels of sensor lines. The same sensing unit measures noise across all channels by switching connections through the multiplexer, eliminating the need for separate measurement devices for each position.
2Productivity
If multiple sensor lines are connected sequentially to sensing unit, then device complexity is reduced, but measurement time increases and productivity decreases
Solution Approach 1:
The multiplexer dynamically switches connections between sensor line groups and the sensing unit based on the measurement phase. During noise measurement, it configures multiple channels to connect simultaneously to the sensing unit, enabling parallel measurement. During touch input sensing, it switches to sequential connection mode, optimizing for different operational requirements.
Solution Approach 2:
The system alternates between different measurement phases: noise measurement portions where multiple channels are connected in parallel, and touch input sensing portions where channels are connected sequentially. This periodic switching optimizes measurement speed during noise measurement while maintaining manageable device complexity during normal operation.
3Measurement precision
If single frequency is used for noise measurement, then measurement process is simple, but measurement precision is insufficient to capture frequency-dependent noise characteristics
Solution Approach 1:
Multiple noise measurement frequencies are pre-configured and stored in the system before actual measurement begins. During the noise measurement portion, the system sequentially applies these pre-selected frequencies to different channels, enabling comprehensive frequency-dependent noise characterization without real-time frequency generation complexity.
Solution Approach 2:
The noise measurement process continuously operates across multiple frequencies by dividing channels into groups and measuring different frequency ranges in parallel. While one group measures at certain frequencies, another group simultaneously measures at different frequencies, maintaining continuous and efficient noise characterization across the entire frequency spectrum.
Data Source
AI summary
A method and a circuit for driving a touch sensor measuring noise and a display device using the same are disclosed. The method of driving the touch sensor includes connecting sensor lines of a plurality of touch sensors to a sensing unit during a noise measurement portion, and driving the sensing unit at previously selected noise measurement frequencies in a state where the sensor lines are connected to the sensing unit or applying a signal of the noise measurement frequencies to the sensor lines to measure a noise of the touch sensors at each of the noise measurement frequencies.