Touch Sensor Multiplexer Resistance Tuning for Uniform Sensing
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Solution Overview
Problem
Sensing voltages applied to touch drivers in display apparatuses are non-uniform due to varying distances between touch sensors and the touch driver, leading to inaccurate and imprecise touch performance.
Innovation Solution
A multiplexer system with transistors having varying on-resistances based on their distance from the touch driver, controlled by different control voltages, ensures precise and uniform sensing data by compensating for wiring losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If touch sensors are placed at different distances from the touch driver, then the touch sensor coverage area is increased, but the sensing voltage uniformity deteriorates
Solution Approach 1:
The patent applies local quality by assigning different on-resistance values to different transistors in the multiplexer based on their position. Transistors closer to the touch driver have higher on-resistance while those farther away have lower on-resistance, creating a localized compensation effect that equalizes sensing voltages across the entire touch sensor array regardless of distance from the driver.
2Device complexity
If transistors in the multiplexer have uniform on-resistance, then the device complexity is reduced, but the sensing signal precision deteriorates
Solution Approach 1:
The patent implements parameter changes by varying the on-resistance parameter of transistors based on their position in the multiplexer. Specifically, transistors closer to the touch driver are designed with higher on-resistance while those farther away have lower on-resistance. This parameter variation compensates for the voltage drop caused by wiring resistance, thereby maintaining sensing signal precision across the entire touch sensor array.
3Length of stationary object
If wiring length between touch sensors and touch driver is increased, then the touch sensor array coverage is expanded, but the wiring loss increases
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for the voltage drop that will occur in the wiring before the signal actually travels through it. Transistors closer to the touch driver (which will experience greater voltage drop due to longer wiring) are designed with higher on-resistance to provide greater initial voltage, effectively counteracting the anticipated wiring loss and ensuring uniform sensing voltages across all touch sensors.
Data Source
AI summary
A touch sensor apparatus may include a multiplexer including a first transistor connected to a first touch sensor and a second transistor connected to a second touch sensor, a touch driver connected to the first touch sensor through the first transistor and connected to the second touch sensor through the second transistor, the first touch sensor disposed at a first distance from the touch driver and the second touch sensor disposed at a second distance shorter than the first distance from the touch driver. A first on-resistance of the first transistor may be smaller than a second on-resistance of the second transistor.