ADC Calibration Scheme for Comparator Offset and Loop Variations
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Solution Overview
Problem
Existing analog to digital converters (ADCs) face challenges in achieving accurate and robust signal conversion due to comparator offsets and process-voltage-temperature variations, which affect communication speed and reliability, particularly in high-speed and high-resolution applications.
Innovation Solution
A two-step calibration scheme is employed, including comparator offset calibration and loop calibration, using on-chip digital-to-analog converters and frequency estimators to adjust thresholds and resonant frequencies, eliminating the need for external devices and optimizing chip area and calibration time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional ADC design is used without calibration, then device complexity is reduced, but manufacturing precision and reliability deteriorate due to comparator offsets and process variations
Solution Approach 1:
The calibration process is divided into two distinct stages: comparator offset calibration and loop calibration. This segmentation allows each calibration task to be handled by dedicated circuitry optimized for its specific function, improving overall calibration precision without excessively increasing total device complexity.
Solution Approach 2:
The ADC includes self-calibration capabilities where the device calibrates itself during manufacturing and operation without requiring external calibration equipment. The on-chip calibration circuits automatically detect and correct comparator offsets and loop filter variations, enabling the device to service its own calibration needs.
2Manufacturing precision
If external calibration devices are used, then manufacturing precision improves, but device complexity and ease of operation worsen due to additional external hardware requirements
Solution Approach 1:
The calibration functionality is extracted from external devices and integrated directly into the ADC chip. The calibration circuits are embedded within the ADC structure, eliminating the need for external calibration equipment and simplifying the overall system operation while maintaining high calibration accuracy.
Solution Approach 2:
The on-chip calibration circuits serve multiple functions: they perform comparator offset calibration, loop filter calibration, and can be integrated with the normal ADC operation. This multi-functionality reduces the need for separate dedicated calibration equipment, simplifying operation while maintaining precision.
3Manufacturing precision
If high-resolution ADC design is implemented, then manufacturing precision improves, but device complexity and productivity worsen due to increased sensitivity to process variations
Solution Approach 1:
Calibration is performed as a preliminary action during the manufacturing process before the ADC is deployed. By completing the calibration setup in advance, the system eliminates the need for time-consuming calibration procedures during operation, thus improving productivity while maintaining high conversion resolution.
Solution Approach 2:
The calibration process adjusts critical parameters such as comparator threshold voltages and loop filter component values to compensate for process variations. By changing these parameters during calibration, the system achieves high conversion resolution without requiring excessive calibration time during manufacturing.
Data Source
AI summary
The systems and methods discussed herein related to analog to digital conversion. An apparatus can include an analog to digital converter including a loop circuit and a comparator circuit. The apparatus can also include a first circuit configured to provide comparator offset calibration for the comparator circuit and a second circuit configured to provide loop calibration for the loop circuit.