ADC Signal Monitoring with Real-Time Reference Calibration
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Solution Overview
Problem
Conventional analog-to-digital converters (ADCs) face output errors due to variations in bandgap reference voltage over temperature ranges, especially when low-order temperature compensation is used, and integrating high-order temperature compensation bandgap reference circuits with ADCs increases design and testing complexity and costs.
Innovation Solution
A signal monitoring system that includes a conversion circuit and a controller, where the controller performs real-time calibration of the output signal based on a trim reference, allowing the use of low-order temperature compensation for the bandgap reference voltage, thereby reducing testing and design complexities and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a bandgap reference circuit with low-order temperature compensation is used, then the structure is simple and cost is reduced, but the reference voltage varies over temperature causing output errors
Solution Approach 1:
The system performs preliminary calibration by measuring the actual reference voltage at a known temperature and storing calibration data before normal operation. This preliminary action allows the system to compensate for temperature variations without requiring complex high-order temperature compensation circuits, thus maintaining structural simplicity while improving output accuracy.
Solution Approach 2:
The system implements feedback by continuously monitoring the reference voltage and using calibration data to adjust measurements. The controller compares actual reference voltage readings with expected values and applies corrections to maintain accuracy across temperature ranges, resolving the contradiction between simple circuit structure and measurement precision.
2Measurement precision
If a bandgap reference circuit with high-order temperature compensation is used, then the reference voltage remains substantially constant over temperature, but the structure becomes complicated and testing cost increases
Solution Approach 1:
The patent extracts the temperature compensation function from the bandgap reference circuit structure itself and implements it separately through software-based calibration and correction algorithms. This separation allows the reference circuit to remain simple while achieving temperature stability through external compensation mechanisms, thus reducing device complexity while maintaining reference voltage stability.
Solution Approach 2:
The system introduces an intermediary calibration process that mediates between the simple reference circuit and the requirement for temperature stability. The calibration routine acts as an intermediary layer that measures, characterizes, and compensates for temperature effects, allowing the use of simple hardware while achieving the precision normally requiring complex circuits.
3Adaptability or versatility
If the bandgap reference circuit is integrated with the ADC into a single chip, then integration is achieved, but design and testing become sensitive to process changes increasing ATE cost and testing time
Solution Approach 1:
The system implements self-service by incorporating self-calibration capabilities that allow the integrated circuit to automatically characterize and compensate for its own process variations. The calibration routine uses built-in resources to measure and correct for manufacturing deviations, reducing sensitivity to process changes and decreasing the need for expensive external ATE and extensive manual testing.
Data Source
AI summary
A signal monitoring system includes a conversion circuit and a controller coupled to the conversion circuit. The conversion circuit converts a reference input to a reference output based on a real-time level of a trim reference and converts a monitored signal to an output signal. The controller calibrates the output signal according to the reference output and according to a predefined reference. The predefined reference is determined by the reference input and by a pre-trimmed level of the trim reference.