ADC Voltage Reference Drift Monitoring and Compensation
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Solution Overview
Problem
Analog-to-digital converters (ADCs) experience significant drift over time due to aging, which affects the accuracy of digital output codes generated, especially in systems requiring long lifetimes and high accuracy, such as battery monitoring in electric vehicles, making it challenging to maintain precise voltage references.
Innovation Solution
A system with a first and second voltage generator, a sensor, and a controller that alternately receives a calibration voltage to monitor and compensate for variations in the voltage reference used by the ADC, allowing for periodic testing and adjustment to maintain accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage reference is used for ADC conversion, then conversion accuracy is improved, but drift over time due to aging deteriorates accuracy
Solution Approach 1:
The system performs preliminary calibration by storing ideal digital output codes corresponding to known calibration voltages before normal operation. These pre-stored codes serve as reference values for later comparison to detect drift, allowing the system to compensate for aging effects without requiring external calibration equipment during operation.
Solution Approach 2:
The system continuously monitors the ADC output when applying calibration voltages and compares actual readings against the stored ideal codes. This feedback mechanism detects drift in the voltage reference over time and triggers compensation actions by adjusting the conversion results based on the detected drift, thereby maintaining accuracy throughout the system lifetime.
2Reliability
If drift compensation is implemented, then accuracy over lifetime is improved, but system complexity increases
Solution Approach 1:
The system uses itself to detect and compensate for drift. The ADC converts calibration voltages generated within the same system, and the microcontroller processes these conversions to detect drift and apply compensation. This self-service approach avoids the need for external calibration equipment or complex additional hardware, reducing overall system complexity while maintaining accuracy over lifetime.
Solution Approach 2:
Instead of continuous complex monitoring, the system performs drift detection periodically by applying calibration voltages at scheduled intervals. This periodic action reduces the computational and hardware complexity compared to continuous monitoring, while still effectively tracking and compensating for drift over the system lifetime.
3Measurement precision
If calibration is performed frequently, then drift compensation accuracy is improved, but loss of time for calibration increases
Solution Approach 1:
The system applies calibration voltages only to specific ADC channels that require drift compensation, rather than calibrating all channels continuously. This partial action approach reduces the total calibration time while maintaining adequate compensation accuracy for the channels that need it, balancing the trade-off between precision and time loss.
Data Source
AI summary
A method and system include a converter such as an analog-to-digital converter (“ADC”) and a controller. The converter is configured to receive a sensor signal, indicative of a physical measured quantity, and generate an output signal based on the sensor signal and the voltage reference. The converter is further configured to alternately receive a calibration voltage in lieu of the sensor signal and generate the output signal based on the calibration voltage and the voltage reference. The controller is configured to compare the output signal based on the calibration voltage and the voltage reference with an expected value of the output signal based on the calibration voltage and an assumed value of the voltage reference to detect variation of the voltage reference, and to compensate the output signal based on the sensor signal and the voltage reference as a function of the detected variation of the voltage reference.