Sigma-Delta Converter Feedback Using Single-Bit DAC Segmentation
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Solution Overview
Problem
Multi-bit sigma delta converters face errors due to mismatched analog elements in the DAC, leading to increased signal-to-noise ratio and total harmonic distortion, which are costly and power-intensive to correct using dynamic element matching techniques.
Innovation Solution
Incorporating a single bit digital-to-analog converter in the feedback path with a feed forward path that adjusts the input voltage using a coefficient based on the multi-bit quantizer's output, eliminating the need for dynamic element matching techniques by ensuring the feedback voltage is always switching between two levels, thus reducing design complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-bit DAC is used in the feedback path, then the converter can achieve higher resolution, but mismatched analog elements cause increased signal-to-noise ratio degradation and total harmonic distortion
Solution Approach 1:
The patent segments the multi-bit feedback DAC into multiple single-bit DACs, each handling a different bit plane of the feedback signal. This segmentation eliminates the mismatch problem in the feedback path since single-bit DACs have only one analog element per bit plane, thereby maintaining high resolution while improving signal-to-noise ratio performance.
Solution Approach 2:
The patent introduces a multi-bit quantizer as an intermediary component between the sigma-delta modulator and the segmented DACs. This multi-bit quantizer processes the modulator output and generates separate bit planes that are then fed to individual single-bit DACs, enabling high-resolution conversion without the mismatch issues of traditional multi-bit feedback DACs.
2Measurement precision
If dynamic element matching techniques are used to correct DAC mismatch errors, then conversion accuracy improves, but design complexity and power consumption increase
Solution Approach 1:
The patent extracts the mismatch correction function from complex dynamic element matching algorithms and implements it through the inherent structure of segmented single-bit DACs. By separating the feedback path into multiple single-bit channels, the system naturally eliminates mismatch errors without requiring additional correction circuitry or complex control logic.
Solution Approach 2:
The patent replaces expensive and complex multi-bit DACs with simpler, more robust single-bit DACs in the feedback path. Although multiple single-bit DACs are used, each individual DAC is simpler and more reliable, and the overall system achieves better performance without requiring complex mismatch correction mechanisms.
3Measurement precision
If a multi-bit DAC is used in the feedback path, then higher conversion resolution is achieved, but the converter area and power consumption increase
Solution Approach 1:
The patent segments the feedback DAC functionality into multiple independent single-bit DACs, each operating at lower power levels. This segmentation allows for more efficient power management and reduces the overall power consumption compared to a single multi-bit DAC, while maintaining the same conversion resolution through the combined output of all segmented channels.
Data Source
AI summary
A sigma delta converter system and method includes a multi bit quantizer circuit coupled to an output of the converter. A single bit analog-to-digital converter circuit is contained in a feedback path of the converter. The converter includes a feed forward path operable to multiply an input voltage by a feed forward coefficient having a value that is a function of a gain control input signal. The gain control input signal can have a value that is a function of the output of the multi bit quantizer.