LED Sensor Crosstalk Cancellation With On-Chip ADC-DAC Control
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Solution Overview
Problem
LED-based biometric optical sensors face challenges with cross talk, latency, and power consumption, which affect their dynamic range and accuracy in measuring vital signs.
Innovation Solution
The proposed solution involves initializing a DAC value and determining if the ADC operates within a predetermined range. When the ADC is within range, a conversion is initiated at a first ADC resolution, and the DAC value is incrementally changed when the ADC is not within range to maintain optimal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If existing control mechanisms use off-chip microcontroller with feedback algorithm to cancel cross talk, then cross talk cancellation is achieved, but latency increases to a fraction of a second
Solution Approach 1:
The patent extracts the cross talk cancellation function from the off-chip microcontroller and implements it directly in the on-chip AFE logic. This removes the need for external feedback algorithms and microcontroller intervention, achieving latency reduction to less than one AFE sample period while maintaining effective cross talk cancellation through direct digital control of the DAC
Solution Approach 2:
The patent merges the cross talk cancellation control logic with the AFE circuitry itself, combining previously separate functions (DAC control, ADC monitoring, and cross talk compensation) into a unified on-chip system. This integration eliminates external communication overhead and achieves real-time latency reduction
2Use of energy by moving object
If AFE sample rate is reduced to minimize power consumption, then power consumption decreases, but latency of feedback loop increases
Solution Approach 1:
The AFE system performs self-adjustment of the DAC value through on-chip logic that automatically monitors ADC output and modifies DAC settings without external intervention. This self-service capability eliminates waiting for external microcontroller responses, reducing feedback latency while maintaining low power operation through optimized sampling strategies
3Device complexity
If cross talk is not cancelled, then device complexity is reduced, but dynamic range of receiver AFE decreases and ADC may saturate
Solution Approach 1:
The patent dynamically changes the DAC control parameter based on real-time ADC output monitoring. By adjusting the DAC value in response to measured conditions, the system maintains optimal dynamic range and prevents ADC saturation without requiring complex fixed-structure control mechanisms
Data Source
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AI summary
Aspects of the present disclosure provide methods and apparatuses for operating an analog-to-digital converter. A method in accordance with an aspect of the present disclosure may comprise initializing a digital-to-analog converter (DAC) value of a DAC, determining whether an analog-to-digital converter (ADC) operates within a predetermined range based on an input to the DAC, initiating a conversion at a first ADC resolution when the ADC is operating within the predetermined range, and incrementally changing the DAC value when the ADC is not operating within the predetermined range.