Touch Sensor IC Signal Processing for Noise Immunity
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Solution Overview
Problem
Capacitive-type touch systems in mobile devices face challenges in achieving true multi-touch detection, high noise immunity, and low power consumption, which existing touch controllers fail to adequately address.
Innovation Solution
A touch screen sensor integrated circuit (IC) that receives current signals generated by mutual capacitance, processes them through a current conveyor and mixer to generate subtracted current signals, and uses a sine-shape resampler to remove high-frequency noise, ultimately converting these signals into touch voltage signals for accurate touch detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional touch controllers are used, then basic touch detection is achieved, but true multi-touch detection accuracy and noise immunity are insufficient
Solution Approach 1:
The patent divides the touch detection process into multiple independent signal processing channels, each handling specific frequency components. The signal is segmented into first frequency component signals and second frequency component signals through separate mixing operations with different modulation signals, allowing independent processing and noise filtering for each segment.
Solution Approach 2:
The patent introduces intermediary processing stages including mixing circuits that combine input signals with modulation signals, and integrating circuits that accumulate signal values over time. These intermediary elements facilitate the separation and processing of different frequency components, improving both accuracy and noise immunity.
2Measurement precision
If signal processing complexity is increased to improve touch detection accuracy, then measurement precision improves, but power consumption increases
Solution Approach 1:
The patent employs periodic modulation signals to encode touch information at different frequency components. By modulating the input signal with periodic carrier signals and then demodulating through mixing operations, the system achieves accurate touch detection through frequency-domain separation without requiring continuous high-power processing across the entire signal bandwidth.
Solution Approach 2:
The patent dynamically adjusts the processing gain applied to different frequency component signals based on their respective signal-to-noise ratios. The integrating circuit selectively accumulates signal values from different mixing operations with varying weights, optimizing power consumption by focusing processing resources on the most informative frequency components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances dynamic range, reduces noise, and effectively removes high-frequency components, improving the accuracy and efficiency of touch detection while maintaining low power consumption.
Implementation Method 1
receiving a plurality of current signals, wherein each current signal is generated according to mutual capacitance
Implementation Method 2
A phase of each of the first sensed current signals may be opposite to a phase of a corresponding one of the second sensed current signals
Implementation Method 3
generating fine current signals by multiplying the subtracted current signals by a sine wave
Data Source
AI summary
A method of operating a touch screen sensor integrated circuit includes: receiving a plurality of current signals through a plurality of pins, wherein each current signal is generated according to mutual capacitance in response to a modulation signal; sensing the current signals and generating a plurality of sensed current signals corresponding to each of the current signals; and generating a plurality of subtracted current signals, wherein each subtracted current signal is generated by performing a subtraction on sensed current signals corresponding to a pair of the pins.