Fingerprint Sensing Circuit With Alternating Integrators for Dynamic Range
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Solution Overview
Problem
Fingerprint sensors using semiconductor capacitive technology face issues with dynamic range reduction due to parasitic capacitance and offset voltage errors, leading to saturation of integrators and increased processing load.
Innovation Solution
A fingerprint detection device employing a multiple integrator system with alternating integration processes and a compensator to adjust output values, reducing parasitic capacitance and offset voltage errors, and increasing the number of integrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single integrator is used to amplify the electrical signal from the touch panel, then the circuit complexity is reduced, but the output dynamic range is reduced due to parasitic capacitance and offset voltage errors causing integrator saturation
Solution Approach 1:
The single integrator is divided into multiple integrators (first integrator and second integrator) that operate in alternating sequences. This segmentation allows each integrator to process signals for only part of the total integration time, preventing any single integrator from saturating due to parasitic capacitance accumulation, thereby extending the overall output dynamic range while maintaining manageable circuit complexity
Solution Approach 2:
The multiple integrators operate in periodic alternating sequences where the first integrator processes signals during one time period and the second integrator processes signals during another time period. This periodic operation allows the system to accumulate integration results over extended periods without any single integrator reaching saturation, effectively increasing the output dynamic range
2Measurement precision
If multiple integrators operate repeatedly many times to increase integration count, then the integration precision is improved, but the processing load of the amplifier increases
Solution Approach 1:
The total integration process is segmented across multiple integrators operating in parallel sequences. Each integrator performs fewer individual integration cycles compared to a single integrator performing all cycles sequentially, distributing the computational burden and reducing the processing load on any single amplifier while maintaining high integration precision through the combined results
Solution Approach 2:
The results from multiple integrators operating in alternating sequences are merged to produce the final integrated output. This combining approach allows the system to achieve high integration precision equivalent to many repeated integrations while the distributed processing across multiple integrators reduces the instantaneous processing load on any single amplifier
3Measurement precision
If the integration time period is extended to increase the number of integrations, then the detection accuracy is improved, but the integration process takes more time
Solution Approach 1:
Multiple integrators operate in periodic alternating sequences, with each integrator active during specific time periods and inactive during others. This periodic operation allows the system to achieve the equivalent of extended integration time through the cumulative effect of multiple integrators working in parallel sequences, thereby improving detection accuracy without proportionally increasing the total integration time
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
Enhances the output dynamic range and reduces processing load by effectively managing parasitic capacitance and offset voltage errors, improving fingerprint detection accuracy.
Implementation Method 1
a first integrator configured to amplify an electrical signal received from the touch panel to a first signal of a first polarity and a second integrator configured to amplify the electrical signal to a second signal of a second polarity
Data Source
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AI summary
Disclosed are a fingerprint detection device and a method therefor. A fingerprint detection device includes: a touch panel; at least one amplifier including a first integrator amplifying an electrical signal received from the touch panel to a signal of a first polarity and a second integrator amplifying the electrical signal to a signal of a second polarity; and a processor configured to control the amplifier to perform a first integration process and a second integration process with respect to a plurality of electrical signals received from a plurality of nodes of the touch panel.