Multi-Bit Sigma-Delta Feedback Loop Split for Low Delay Stability
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Solution Overview
Problem
Conventional multi-bit sigma/delta converters face issues with excess loop delay, which reduces dynamic range and stability due to the implementation of dynamic element matching in the innermost feedback loop, leading to circuit complexity and limitations to flash analog/digital converters.
Innovation Solution
Dynamic element matching is performed in the outer feedback path, allowing the inner feedback digital/analog converter to directly convert the digital output signal into the inner feedback signal, reducing excess loop delay and enhancing stability and linearity by filtering noise caused by this delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dynamic element matching is performed in the innermost feedback loop, then linearity is improved, but excess loop delay increases and stability deteriorates
Solution Approach 1:
The feedback loop is segmented into two separate loops: an inner feedback loop that processes the most significant bits without dynamic element matching to maintain stability, and an outer feedback loop that processes less significant bits with dynamic element matching to improve linearity. This segmentation allows each loop to be optimized for its specific function.
Solution Approach 2:
Different quality requirements are applied to different parts of the feedback system. The inner loop uses fixed element matching for critical stability requirements, while the outer loop employs dynamic element matching for linearity improvement. This local differentiation of matching strategies optimizes overall converter performance.
2Manufacturing precision
If dynamic element matching is performed in the innermost feedback loop, then linearity is improved, but device complexity increases
Solution Approach 1:
The feedback loop is segmented into two separate loops: an inner feedback loop that processes the most significant bits without dynamic element matching to maintain stability, and an outer feedback loop that processes less significant bits with dynamic element matching to improve linearity. This segmentation allows each loop to be optimized for its specific function.
Solution Approach 2:
Dynamic element matching is applied partially - only to the outer feedback loop processing less significant bits, rather than to the entire feedback system. This partial application achieves sufficient linearity improvement while avoiding the excessive complexity of full-system dynamic element matching.
3Stability of the object's composition
If the inner feedback digital/analog converter directly converts the digital output signal, then excess loop delay is reduced and stability is enhanced, but linearity may deteriorate
Solution Approach 1:
The feedback loop is segmented into two separate loops: an inner feedback loop that processes the most significant bits without dynamic element matching to maintain stability, and an outer feedback loop that processes less significant bits with dynamic element matching to improve linearity. This segmentation allows each loop to be optimized for its specific function.
Solution Approach 2:
Different quality requirements are applied to different parts of the feedback system. The inner loop uses fixed element matching for critical stability requirements, while the outer loop employs dynamic element matching for linearity improvement. This local differentiation of matching strategies optimizes overall converter performance.
Data Source
AI summary
A multi-bit sigma/delta converter for converting an analog input signal into a digital output signal comprises a filter device for filtering the analog input signal which is added to a feedback signal to form an intermediate signal. An integrator device for integrating the filtered intermediate signal added to an inner feedback signal forms a quantizer input signal. A quantizer device quantizes the quantizer input signal to form the digital output signal. An inner feedback digital/analog converter is provided for converting the digital output signal directly into the inner feedback signal. A DEM device for performing dynamic element matching on the digital output signal and providing a matched digital signal is provided and a feedback digital/analog converter for converting the matched digital signal into the feedback signal is implemented.