Single-Node Channel Driver Circuit for Faster Touch Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Projected capacitive touch sensors face challenges in accurately determining touch locations due to large parasitic capacitances, which require multiple integration cycles, increasing the time to make a determination and affecting user experience, especially in larger displays.
Innovation Solution
A channel driver circuit is implemented that employs a differential module, sigma-delta module, and driver module to generate a low impedance virtual signal and receive load-modified signals, while simultaneously detecting changes, using noise shaping to reduce noise and improve signal accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple integration cycles are used to determine touch locations, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent changes the integration method from multiple sequential integration cycles to a single integration cycle with modified weighting parameters. The weighting scheme assigns different importance to different samples within the single cycle, effectively capturing the necessary measurement precision through parameter optimization rather than repeated cycles.
Solution Approach 2:
The patent performs preliminary signal conditioning and noise filtering before the single integration cycle, preparing the signal in advance so that one integration cycle suffices for accurate measurement. This preliminary processing reduces the need for multiple integration cycles while maintaining measurement precision.
2Measurement precision
If noise shaping is applied, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces noise shaping as an intermediary processing stage between signal acquisition and measurement. This intermediary component modifies the noise spectrum to push quantization noise away from the measurement band, improving signal accuracy without requiring fundamental changes to the core measurement circuitry.
Data Source
AI summary
A channel driver circuit includes a differential module and a driver module. In some examples, the channel driver circuit also includes a sigma-delta module. The differential module receives, via a single node of a load, a channel driving signal that is provided to the load at the single node (e.g., that is based on an electrical characteristic of the load) and generates an analog error signal that is based on the channel driving signal and a reference signal. The driver module is coupled to the differential module and generates the channel driving signal based on the analog error signal or a digital error signal corresponding to the analog error signal and transmits the channel driving signal via the single node to the load. The channel driver circuit simultaneously transmits the channel driving signal to the load at the single node and senses the channel driving signal at the single node.