DAC Background Calibration with Redundant Cells and Error-Tone Feedback
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Solution Overview
Problem
Digital-to-analog converters (DACs) face imperfections leading to noise and spurs in their output, which degrade performance and can affect other signal chain components, and existing calibration techniques are either impractical or inefficient, especially for dynamic errors.
Innovation Solution
The proposed solution involves background calibration methods using redundant DAC cells to generate reference and calibration tones with opposite polarities, allowing for efficient detection and minimization of static and dynamic errors within a single frequency bin, thereby reducing processing overhead and maintaining minimal impact on normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration techniques are used to improve DAC accuracy, then measurement precision is improved, but device complexity and processing overhead increase significantly
Solution Approach 1:
The patent extracts the calibration function into separate dedicated calibration DAC cells that are distinct from the normal operational DAC cells. This allows calibration operations to be performed independently without interfering with normal DAC operation, reducing the complexity burden on the main DAC structure while maintaining calibration accuracy.
Solution Approach 2:
The patent introduces an intermediary feedback path that carries error signals from the DAC output back to the calibration circuitry. This feedback mechanism serves as a mediator that enables precise error detection and correction without requiring complex direct measurement systems, thereby improving measurement precision while managing device complexity.
2Measurement precision
If foreground calibration is performed to achieve high calibration accuracy, then measurement precision is improved, but productivity and operational continuity deteriorate due to processing overhead
Solution Approach 1:
The patent implements preliminary calibration actions by pre-configuring redundant DAC cells and calibration weight sets before actual calibration is needed. The calibration infrastructure is prepared in advance, allowing calibration to be performed quickly when required without significant operational disruption, thus maintaining both high accuracy and productivity.
Solution Approach 2:
The patent enables periodic calibration operations where the DAC can be calibrated at scheduled intervals rather than requiring continuous or frequent calibration. This periodic approach maintains measurement precision through regular calibration while minimizing the impact on productivity by limiting calibration disruptions to specific time windows.
3Measurement precision
If multiple frequency bins are used for calibration to reduce noise, then measurement precision is improved, but loss of time and processing overhead increase
Solution Approach 1:
The patent applies partial action by using a single frequency bin for calibration instead of multiple frequency bins. This is made possible by the high precision of the feedback path and the use of redundant calibration cells, which compensate for the reduced measurement diversity. This approach maintains sufficient measurement precision while significantly reducing the time and processing overhead associated with analyzing multiple frequency bins.
4Measurement precision
If calibration is performed at full signal amplitude to maximize accuracy, then measurement precision is improved, but use of energy and power consumption increase
Solution Approach 1:
The patent implements dynamic calibration where the calibration stimulus amplitude and frequency can be adjusted during the calibration process. This allows the system to optimize the balance between measurement precision and power consumption by adapting calibration parameters to current operating conditions, rather than always using maximum amplitude signals.
Solution Approach 2:
The patent changes calibration parameters such as stimulus amplitude, frequency, and duration based on operational requirements. By dynamically adjusting these parameters, the system can achieve sufficient calibration accuracy with lower power consumption signals, resolving the contradiction between measurement precision and energy usage.
Data Source
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AI summary
Techniques that enable calibration of digital-to-analog Converters (DACs) with minimal processing overhead. A single frequency bin can be used to calibrate errors between bits. A low frequency feedback path can be included into a low frequency low power ADC to determine the error signal that exists in the calibration bin. The bits are calibrated when this error signal is minimized. The calibration techniques described provide an extremely efficient and optimal calibration at the DAC output of both static and dynamic errors.