Reconfigurable Touch Front-End Circuit for Low-Noise ADC Conversion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Touch processing systems face challenges in reducing power consumption and area while accurately detecting touch events, particularly due to issues with parasitic noise and electromagnetic interference in large sensor arrays, which affect detection speed and accuracy.
Innovation Solution
A front-end circuit is designed with a reconfigurable circuit that includes switches, capacitors, and a controller to perform analog-to-digital conversion and touch processing, utilizing phases for accumulation and conversion of input signal deviations, and employing cyclic analog-to-digital conversion to minimize noise and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large sensor array is used to improve touch detection accuracy, then measurement precision is improved, but area and power consumption increase
Solution Approach 1:
The sensor array is divided into multiple blocks, with each block containing multiple sensing electrodes. This segmentation allows the large sensor array to be managed in smaller units, reducing the area occupied by individual circuit components while maintaining overall detection accuracy across the entire array.
Solution Approach 2:
The front-end circuit is designed to perform multiple functions including amplification, integration, and analog-to-digital conversion using shared components. The amplifier and integrator use the same capacitor and switch resources sequentially, reducing the total area required compared to having dedicated components for each function.
2Measurement precision
If a large sensor array is used to improve touch detection accuracy, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The front-end circuit operates in periodic phases including integration period and conversion period. During the integration period, the amplifier accumulates the input signal; during the conversion period, the accumulated signal is converted to digital form. This periodic operation allows efficient use of power by activating components only when needed rather than continuously.
Solution Approach 2:
The same capacitor serves dual purposes as both an integration capacitor during the integration period and as a sampling capacitor during the conversion period. This multi-functionality reduces the total number of capacitors needed, thereby reducing overall power consumption while maintaining detection accuracy.
3Ease of manufacture
If traditional analog-to-digital conversion is used, then conversion function is achieved, but noise and electromagnetic interference increase
Solution Approach 1:
An integrator is introduced as an intermediary stage between the amplifier and the analog-to-digital converter. The integrator accumulates the amplified signal over time, which averages out high-frequency noise and electromagnetic interference. This intermediary integration step allows the ADC to convert a cleaner, more stable signal, improving detection accuracy while reducing the impact of harmful electromagnetic factors.
4Reliability
If dedicated components are used for each function, then reliability is improved, but device complexity and area increase
Solution Approach 1:
The front-end circuit uses a reconfigurable architecture where the same capacitor and switches serve multiple functions at different times. During the integration period, the capacitor acts as an integration capacitor; during the conversion period, it becomes a sampling capacitor. This time-multiplexed approach maintains circuit reliability through proper signal accumulation while reducing device complexity and area by eliminating the need for separate dedicated components for each function.
Data Source
Figure 1A
Figure 1B
Figure 2
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.