Sigma-Delta ADC Metastability Compensation Outside the Feedback Loop
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Solution Overview
Problem
Sigma-Delta modulators face stability issues at high sampling frequencies due to parasitic poles and delays, and metastability errors in the quantizer can degrade performance, especially for small input signals, leading to reduced signal-to-noise ratio and dynamic range.
Innovation Solution
A data processor with a metastability compensation module that includes a correction module outside the feedback loop, which determines and corrects metastability errors in the quantized output signal, improving the signal-to-noise ratio without affecting the stability of the data processing module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sampling frequency is increased to improve productivity, then the processing speed increases, but metastability errors increase and signal-to-noise ratio degrades
Solution Approach 1:
The patent divides the quantizer output processing into two separate paths: a main feedback path that maintains stability and a correction path that handles metastability errors. The correction module segments the metastability error detection and correction functions from the main quantizer, allowing high-speed operation while maintaining signal quality through dedicated error compensation circuitry.
2Measurement precision
If the quantizer regeneration time is increased to reduce metastability errors, then measurement precision improves, but the feedback loop stability deteriorates due to increased delay
Solution Approach 1:
The patent extracts the metastability error correction function from the main feedback loop by placing the correction module outside the loop. This allows the quantizer to operate with sufficient regeneration time for accuracy while the correction module handles metastability errors without introducing additional delays into the critical feedback path, thus maintaining loop stability.
Solution Approach 2:
The correction module acts as an intermediary between the quantizer output and the downstream signal processing. It detects metastability errors in the quantizer output and provides corrected signals without affecting the feedback loop operation, thereby mediating between the need for accurate quantization and the need for stable feedback loop operation.
3Reliability
If a correction module is added to reduce metastability errors, then signal-to-noise ratio improves, but device complexity increases
Solution Approach 1:
The correction module is configured to receive the quantizer output and autonomously detect and correct its own metastability errors without requiring external intervention or complex control logic. This self-service approach simplifies the overall system architecture by making the correction function independent and self-contained, reducing the complexity burden despite adding error correction capability.
Data Source
AI summary
A data processor is disclosed. The data processor includes a data processing module. The data processing modules includes an input for receiving an input signal, an output for providing a quantized output signal, a combining unit configured to combine a feedback signal from the output with the input signal and a quantizer configured to provide the quantized output signal based on the combined signal. The data processor further includes a correction module configured to receive the quantized output signal, generate a full-scale digital signal based on the quantized output signal, determine a metastability error in the full-scale digital signal and provide a compensated output signal based on the quantized output signal and the determined metastability error.