ADC Background Calibration for Aperture Timing Bubble Errors
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Solution Overview
Problem
High-speed analog to digital converters (ADCs) face challenges in maintaining even threshold spacing due to aperture timing errors, leading to reduced effective resolution and the occurrence of 'bubbles' or 'sparkle codes' in data conversion, which disrupt accurate signal representation.
Innovation Solution
A method for background calibration of aperture center errors in ADCs, where a signal derivative is calculated at detected low sampler outputs between high outputs, and the timing of selected samplers is adjusted to compensate for timing errors, effectively removing aperture center errors without disrupting normal signal flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed ADC operation is implemented, then conversion speed is improved, but aperture timing errors increase causing threshold spacing non-linearity
Solution Approach 1:
The patent applies preliminary action by performing background calibration that continuously monitors and corrects aperture timing errors during normal ADC operation. The calibration process proactively adjusts sampler timing offsets before they accumulate significant errors, maintaining threshold spacing linearity without disrupting high-speed conversion operations.
Solution Approach 2:
The patent changes the timing parameter of samplers dynamically through background calibration. By continuously adjusting the sampling instant of individual comparators based on measured aperture errors, the system maintains accurate threshold spacing despite high-speed operation-induced timing drifts.
2Measurement precision
If foreground calibration is performed to correct aperture errors, then measurement precision is improved, but system productivity decreases due to signal flow disruption
Solution Approach 1:
The patent implements continuity of useful action through background calibration that operates continuously during normal ADC signal conversion. The calibration process runs in parallel with data conversion, allowing both calibration and productivity to coexist without interrupting the useful signal flow through the ADC.
Solution Approach 2:
The patent uses an intermediary approach by introducing a calibration signal path that operates alongside the normal data signal path. The background calibration uses intermediate measurements and adjustments that do not block or disrupt the primary data conversion function, allowing both calibration and data processing to proceed simultaneously.
3Device complexity
If aperture timing errors are left uncorrected, then device complexity is reduced, but data conversion accuracy deteriorates due to bubble codes
Solution Approach 1:
The patent applies self-service by implementing an automatic background calibration system that continuously monitors and corrects its own aperture timing errors without external intervention. The ADC system serves itself by detecting timing offsets and automatically adjusting sampler timing, maintaining high reliability without adding complex manual calibration procedures.
Data Source
AI summary
A method of background calibration of aperture center errors in a data communication system is provided. In an implementation, in response to detection of a low sampler output (“0”) in between two high sampler outputs (“1”), the method includes: determining a direction of an ADC output signal at the time of the detected low output; and adjusting timing at a selected sampler based on the determined signal direction. In an example implementation, the method includes watching for bubbles in the thermometer code output, and estimating the first derivative of the signal at the time of the bubble, then estimating the sign of the errors. In an example implementation, the errors are used in a control loop to reduce the aperture center error.