Self-Calibrating Data Converter for Capacitor Mismatch Correction
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Solution Overview
Problem
High-resolution data converters face challenges in achieving accurate conversions due to capacitor mismatch issues, leading to non-monotonicities and reduced input ranges, which are costly to address with existing calibration methods.
Innovation Solution
A data conversion system that employs self-calibration techniques, including the use of oversized scaling capacitors and digital calibration methods to compensate for capacitor mismatches, maintaining full input range and reducing conversion errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods are used to correct capacitor mismatch, then conversion accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The data converter performs self-calibration using its own internal resources. The capacitor array is reused in a calibration mode where the DAC converts digital codes to analog voltages, and the ADC measures these voltages to determine calibration values. This eliminates the need for external calibration equipment and reduces system complexity while maintaining high conversion accuracy.
Solution Approach 2:
The calibration process is performed in advance during manufacturing or initialization, storing calibration values in lookup tables or memory. These pre-computed calibration values are then applied during normal operation to compensate for capacitor mismatch, improving conversion accuracy without adding complexity to the real-time conversion path.
2Measurement precision
If capacitor mismatch is corrected through manufacturing precision, then conversion accuracy is improved, but manufacturing cost and difficulty increase
Solution Approach 1:
Instead of investing in expensive precision manufacturing processes to achieve tight capacitor matching, the patent uses inexpensive digital calibration values stored in memory to compensate for mismatch. The calibration data acts as a low-cost correction that achieves high accuracy without requiring precision analog manufacturing.
Solution Approach 2:
The patent transforms the problem from an analog domain issue (capacitor physical dimensions) to a digital domain solution (calibration values). By measuring the actual capacitor ratios and storing digital correction factors, the system compensates for manufacturing variations without requiring tighter manufacturing tolerances.
3Measurement precision
If high-resolution conversion is achieved, then measurement precision is improved, but input range is reduced due to non-monotonicities
Solution Approach 1:
The calibration process uses feedback from the ADC to measure the actual output of the DAC for various digital codes. These measurements are used to compute calibration values that correct non-monotonicities in the transfer function, ensuring that the converter maintains both high resolution and full input range by eliminating spurious transitions.
Data Source
AI summary
A data converter for converting analog signals to digital signals, or for converting digital signals to analog signals is provided. In one embodiment, a production self-test is provided. In one embodiment, a high-speed lower-resolution method or mode for a data converter is provided. In one embodiment, a differential data converter with a more stable comparator common mode voltage is provided. In one embodiment, the input range of a digitally calibrated data converter is provided and maintained so that there is no loss in input range due to the calibration. In one embodiment, digital post-processing of an uncalibrated result using a previously stored calibration value is provided.