Capacitive Sensing Noise Reduction via Low-Noise Period Synchronization
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Solution Overview
Problem
Capacitive sensing performance in input devices is hindered by noise introduced by interfering circuitry within the same power domain, affecting the accuracy of touch and proximity detection.
Innovation Solution
A processing system is configured to determine low-noise periods and synchronize susceptible processing functions, such as ADC operations, to occur during these periods, reducing noise interference and improving sensing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ADC operations are performed continuously to process sensor signals, then processing speed and productivity are improved, but noise interference from interfering circuitry increases, degrading measurement precision
Solution Approach 1:
The patent implements periodic ADC operations synchronized with display update timing. The ADC circuitry performs conversions only during low-noise periods between display updates, creating a periodic processing pattern that avoids high-noise periods. This resolves the contradiction by maintaining adequate processing speed through regular periodic operations while achieving measurement precision by executing only during favorable noise conditions.
2Speed
If display updates are performed at high frequency to improve visual performance, then display refresh rate is improved, but noise events from interfering circuitry increase, degrading sensing performance
Solution Approach 1:
The patent extracts and identifies discrete noise events generated by interfering circuitry during display updates. By detecting these noise events and their timing patterns, the system separates noise-free time periods from noisy periods. This allows ADC operations to be scheduled exclusively during extracted low-noise intervals, resolving the contradiction between high display refresh rates and sensing performance.
3Productivity
If multiple processing functions are performed simultaneously to improve productivity, then system throughput is improved, but noise susceptibility increases, degrading measurement precision
Solution Approach 1:
The patent segments processing functions into distinct time slots based on noise characteristics. ADC operations are segmented to occur only during low-noise periods, separated from high-noise display update operations. This temporal segmentation allows multiple functions to be performed throughout the cycle while protecting measurement precision by isolating sensitive ADC operations from noisy periods.
Data Source
AI summary
An input device, system, and processing system are disclosed for a display device with an integrated sensing device. The input device comprises a plurality of sensor electrodes, and a processing system coupled with the plurality of sensor electrodes. The processing system is configured to determine one or more low-noise periods associated with display update timing of the display device, and process, during the determined one or more low-noise periods, resulting signals received from the plurality of sensor electrodes.