ADC Sampler and Amplifier Calibration via Dither Counting
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Solution Overview
Problem
Analog-to-digital converters (ADCs) face challenges in efficiently detecting and correcting non-linearities and non-idealities in their circuits, leading to performance degradation and increased power consumption, particularly in pipelined ADCs with MDAC amplifiers, where existing calibration techniques suffer from long convergence times, sensitivity to non-idealities, and compromised dynamic range.
Innovation Solution
An improved calibration technique uses a dither signal injected into the analog circuit to expose non-linear or non-ideal behavior in the digital domain, employing a counting approach that isolates non-linearities through differential analysis of output values with and without dither, allowing for efficient correction of second and third-order distortions without requiring analog changes to the ADC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing calibration techniques are used in pipelined ADCs, then non-linearities can be corrected, but convergence time is long and dynamic range is compromised
Solution Approach 1:
The patent applies preliminary action by injecting a dither signal before the actual calibration measurement to pre-condition the system and expose non-linearities. The dither signal is added to the input signal before conversion, allowing the system to detect and correct non-linearities in samplers and amplifiers before they affect the main signal path, thereby reducing convergence time while maintaining correction accuracy.
2Measurement precision
If existing calibration techniques are used, then non-linearities can be detected, but power consumption increases
Solution Approach 1:
The patent implements self-service by using the ADC's own dither signal (already present in the system for other purposes) to perform calibration measurements. Instead of requiring separate external test equipment or additional calibration circuits, the system uses its internally generated dither signal to detect and correct non-linearities, thereby reducing power consumption while maintaining detection accuracy.
3Measurement precision
If existing calibration techniques are used, then non-linearities can be corrected, but the system becomes sensitive to non-idealities
Solution Approach 1:
The patent uses the dither signal as an intermediary to indirectly measure non-linearities. Instead of directly measuring the non-idealities in samplers and amplifiers, the dither signal modulates these non-linearities into the output spectrum, where they can be detected and corrected without being directly affected by other non-idealities in the system, thereby reducing sensitivity to non-idealities while maintaining correction capability.
Data Source
AI summary
Analog circuits are often non-linear, and the non-linearities can hurt performance. Designers would trade off power consumption to achieve better linearity. An efficient and effective calibration technique can address the non-linearities and reduce the overall power consumption. A dither signal injected to the analog circuit can be used to expose the non-linear behavior in the digital domain. To detect the non-linearities, a counting approach is applied to isolate non-linearities independent of the input distribution. The approach is superior to and different from other approaches in many ways.