ADC Background Calibration Using Random Capacitor Sampling
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Solution Overview
Problem
Analog-to-digital converters (ADCs) face issues due to capacitance variations during manufacturing, leading to abnormal digital signals, which existing calibration methods fail to address effectively, affecting accuracy and reliability.
Innovation Solution
A digital background calibration circuit incorporating a digital random number generator and switches to control sampling capacitors, allowing for self-calibration by generating a digital sequence during the calibration period, reducing reliance on external signals and enhancing accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional calibration methods are used, then external calibration signals are required, but this increases device complexity and reduces ease of operation
Solution Approach 1:
The ADC system performs self-calibration by using its own internal resources (sampling capacitors, switches, and digital logic) to generate calibration signals and adjust its own capacitance weights, eliminating the need for external calibration equipment or signals
Solution Approach 2:
The sampling capacitors and switches serve dual purposes: they function as normal ADC components during conversion and as calibration components during the calibration phase, allowing the same hardware to perform multiple functions without adding extra dedicated calibration hardware
2Measurement precision
If capacitance variations are not corrected, then manufacturing simplicity is maintained, but measurement precision deteriorates
Solution Approach 1:
The system uses feedback by comparing the actual output of the ADC with expected values during calibration, then adjusting the capacitance weights of sampling capacitors based on this feedback to minimize errors and improve measurement precision
Solution Approach 2:
The calibration process changes the electrical parameters (capacitance weights) of the sampling capacitors to compensate for manufacturing variations, thereby improving measurement precision without requiring physical redesign or selection of components
3Productivity
If manual calibration is performed, then calibration accuracy can be controlled, but productivity decreases due to time-consuming calibration processes
Solution Approach 1:
The calibration is performed periodically or on-demand rather than continuously, allowing the ADC to operate at full speed for normal conversions while dedicating specific time intervals for calibration, thus maintaining both productivity and precision
Solution Approach 2:
The calibration process is performed in advance during manufacturing or initialization, so that by the time the ADC is deployed for normal operation, the capacitance weights are already optimized, eliminating the need for time-consuming calibration during actual use
Data Source
AI summary
A digital background calibration circuit including a digital random number generator, an analog-to-digital converter (ADC) and a plurality of switches is provided. The digital random number generator is configured to generate a first digital sequence having a plurality of bits. The ADC includes a plurality of sampling capacitors. The switches receive the first digital sequence and are coupled to the sampling capacitors. During a calibration period, the digital random number generator controls the sampling capacitors via the switches to sample the first digital sequence.