Comparator Calibration Search Windows for High-Throughput ADCs
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Solution Overview
Problem
High-speed digital communication systems face challenges in calibrating multiple comparators due to process variation, supply voltage variation, and temperature variation, which affect symbol error rates and overall system performance, necessitating efficient and precise calibration methods to minimize downtime and maintain throughput.
Innovation Solution
A method for calibrating multiple comparators in integrated circuits involves determining an initial search window based on a previous comparator's setting, refining the search window based on output signals, and sequentially trying calibration settings until a transition is detected, using a nonvolatile memory to store calibration settings and adjust reference voltages to compensate for offset voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If periodic calibration of comparators is performed to compensate for voltage offset changes, then precision is improved, but receiver throughput deteriorates due to calibration downtime
Solution Approach 1:
The patent applies preliminary action by using the calibration setting from the previous comparator to pre-determine an initial search window for the current comparator. This preliminary estimation based on correlated settings reduces the calibration search space before actual calibration begins, minimizing calibration time while maintaining precision.
2Measurement precision
If exhaustive search is performed for each comparator calibration setting, then calibration precision is improved, but calibration time increases
Solution Approach 1:
The patent performs preliminary action by determining an initial search window for the current comparator based on the calibration setting of the previous comparator. This preliminary step narrows down the calibration search space significantly, allowing the system to achieve precise calibration settings without performing exhaustive searches across the entire parameter range.
Solution Approach 2:
The patent applies feedback by using the calibration setting result from the previous comparator to inform and constrain the search space for the current comparator. This feedback mechanism exploits the correlation between adjacent comparator settings, enabling the system to focus the search within a refined window that is more likely to contain the optimal calibration setting, thereby reducing calibration time while maintaining precision.
Data Source
AI summary
Flash analog to digital converters and other types of integrated circuits having multiple comparators may employ calibration methods and firmware to efficiently compensate the various offset voltages of the multiple comparators. One illustrative integrated circuit includes: multiple comparators each configured to provide a comparator output signal indicating whether an input signal exceeds a reference voltage by more than an offset voltage, the multiple comparators including a current comparator and a previous comparator; and a controller configured to perform a search to select a calibration setting for each of the comparators in turn, the controller determining an initial search window for the current comparator based on a calibration setting selected for the previous comparator.