Reconfigurable Touch ADC Front-End Circuit for Noise-Resistant Sensing
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Solution Overview
Problem
Touch systems face challenges in accurately detecting touch events with reduced power consumption and area, particularly due to issues like parasitic noise and electromagnetic interference, especially as the size of sensor arrays increases.
Innovation Solution
A front-end circuit with a reconfigurable circuit configuration, including capacitors and switches, that accumulates signal deviations during an integration period and converts them into digital signals during a conversion period, using a controller to manage the switches and capacitors to minimize noise and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensor array size is increased to improve touch detection coverage, then measurement precision is improved, but parasitic noise and electromagnetic interference increase
Solution Approach 1:
The patent employs periodic sampling of the input signal at different phases (first phase and second phase) to accumulate deviations over time. By periodically switching between phases and accumulating the differences, the circuit enhances the detection of touch signals while averaging out random parasitic noise, thus improving signal-to-noise ratio without requiring larger sensor arrays
Solution Approach 2:
The patent uses feedback capacitors (second capacitor and third capacitor) to store and feed back the accumulated deviations from previous phases. This feedback mechanism allows the circuit to integrate signal deviations over multiple phases, enhancing the detection of genuine touch signals while rejecting uncorrelated parasitic noise, thereby improving measurement precision without increasing sensor array size
2Measurement precision
If front-end circuit components are increased to improve signal processing capability, then measurement precision is improved, but device area increases
Solution Approach 1:
The patent designs the front-end circuit with components that serve multiple functions: the amplifier provides both signal amplification and virtual ground generation; the capacitors function as both sample-and-hold elements and feedback elements at different phases; the switches enable both signal routing and phase switching. This multi-functionality allows high-precision signal processing without requiring additional dedicated components, thus minimizing circuit area
Solution Approach 2:
The patent employs dynamic reconfiguration of the circuit topology through switches that change the connection states of capacitors and amplifiers between different phases. During the integration period, the circuit dynamically switches between sampling the input signal, providing virtual ground, and applying feedback. This dynamic operation allows a single set of components to perform multiple processing functions, reducing the overall circuit area while maintaining high measurement precision
3Measurement precision
If integration period is extended to improve signal accumulation, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent uses periodic phase switching within a fixed integration period, where the circuit alternates between first phase and second phase sampling. By accumulating deviations through these periodic phase transitions rather than simply extending the integration time, the circuit achieves improved signal accumulation accuracy while maintaining a limited integration period, thus controlling power consumption
Solution Approach 2:
The patent maintains continuous useful action by having the amplifier operate continuously during the integration period, with capacitors continuously accumulating deviations through periodic phase switching. This continuous operation of the core amplification function, combined with periodic sampling, allows effective signal accumulation without requiring extended integration periods, thereby limiting power consumption while improving measurement precision
Data Source
AI summary
A touch processing circuit includes: a front-end circuit including an amplifier, a first capacitor, a second capacitor, a third capacitor, and a plurality of switches each having two ends that are selectively connected each other, the front-end circuit being configured to process an input signal varying according to a touch; and a controller controlling the plurality of switches so that the front-end circuit is configured as a first circuit that accumulates deviation of the input signal between a first phase and a second phase during an integration period and a second circuit that converts the accumulated deviation into a digital signal during a conversion period.