ADC Output Drift Correction Using Reference Voltage Calibration
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Solution Overview
Problem
In optical communication, maintaining a constant operating temperature of photodiodes is crucial for optimal performance, but existing technologies lack effective mechanisms to accurately measure and correct temperature drifts in analog-to-digital converters (ADCs), leading to instability in ADC outputs over time and temperature.
Innovation Solution
The proposed solution involves determining first and second digital codes representing reference voltages to calculate and correct gain and offset drifts in the signal chain of ADCs, using techniques such as differential measurement of base-emitter voltage across a diode to determine temperature and employing digital post-processing to adjust ADC outputs, thereby achieving temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature compensation techniques are implemented, then ADC output stability is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before normal operation to extract offset and gain values. The system pre-determines compensation parameters (offset and gain) during a calibration phase, which are then stored and applied during actual ADC operation. This allows the system to compensate for temperature drift without adding complex real-time correction circuitry, as the compensation values are prepared in advance.
Solution Approach 2:
The patent uses an intermediary approach by introducing a separate calibration circuit and digital processing block that acts as a mediator between the ADC and the output. This intermediary calibration system measures reference voltages, calculates offset and gain drift, and applies corrections digitally. This separates the compensation function from the main ADC circuitry, improving stability without significantly complicating the core conversion process.
2Measurement precision
If calibration measurements are performed, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The calibration measurements are performed as a preliminary action during manufacturing or initial setup, before the ADC enters normal operation. By completing the offset and gain extraction in advance, the system achieves high measurement precision without incurring time penalties during actual use. The calibrated parameters are stored and reused, making the precision improvement permanent without recurring time costs.
Solution Approach 2:
The patent implements periodic action by allowing recalibration at scheduled intervals or when temperature thresholds are exceeded. Instead of continuous calibration that would waste time, the system performs measurements periodically or event-driven (e.g., when temperature changes significantly). This balances measurement precision needs with time efficiency, recalibrating only when necessary to maintain accuracy.
3Reliability
If temperature monitoring is implemented, then reliability is improved, but use of energy increases
Solution Approach 1:
The patent applies self-service by using the ADC's existing circuitry to monitor temperature effects. The calibration circuit uses the same reference voltages and signal paths as the normal ADC operation, allowing the system to self-diagnose temperature drift without separate monitoring hardware. The digital processing block analyzes the same data streams already being processed, enabling temperature compensation without additional energy-consuming sensors or circuits.
Solution Approach 2:
The patent implements universality by making the calibration circuit multi-functional. The same circuitry that measures reference voltages for offset and gain extraction also serves as the temperature monitoring mechanism. By analyzing drift in the reference voltage measurements, the system infers temperature effects and applies corrections. This eliminates the need for separate temperature sensors, reducing overall energy consumption while maintaining reliability.
Data Source
AI summary
Techniques are described that can be used to extract an offset and a gain of a signal chain, which can be used for digital correction of an analog-to-digital converter (ADC) output to help achieve a life time and temperature stable ADC output. For example, using various techniques, a value for a voltage reference VREF and a value for ground (GND) (or other reference voltage) can be converted, which can then be used to determine gain and offset, respectively, of the signal chain.