Delta-Sigma Multiplying DAC With Integrated Noise Reconstruction Filter
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Solution Overview
Problem
Digital to analog converters face challenges in achieving high accuracy due to quantization noise leakage into the signal band caused by non-linearity in analog circuits, which degrades noise performance and reduces effective resolution.
Innovation Solution
Integrating a reconstruction filter within the delta sigma modulator based multiplying-DAC to filter out high frequency quantization noise before it reaches the amplifier stage, combined with dynamic element matching and chopping techniques to address non-linearity and flicker noise issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reconstruction filter is integrated within the delta sigma modulator based multiplying-DAC, then quantization noise is reduced and noise immunity is improved, but device complexity increases
Solution Approach 1:
The patent integrates the reconstruction filter directly within the multiplying-DAC structure, merging two separate functions (filtering and digital-to-analog conversion) into a single unified circuit. This integration reduces quantization noise leakage into the signal band while avoiding the need for separate external filter components, thereby improving effective resolution without proportionally increasing overall device complexity.
Solution Approach 2:
The reconstruction filter is divided into multiple stages distributed throughout the multiplying-DAC structure. By segmenting the filtering function across multiple operational stages rather than using a single complex filter, the patent achieves effective noise reduction while maintaining manageable circuit complexity at each individual stage.
2Reliability
If dynamic element matching and chopping techniques are applied, then non-linearity and flicker noise are reduced, but device complexity increases
Solution Approach 1:
The patent employs dynamic element matching that continuously adjusts element assignments based on measured performance characteristics, and chopping techniques that dynamically switch circuit elements at specific frequencies to modulate and reduce flicker noise. These dynamic adaptations improve noise performance and linearity while the techniques are implemented through control logic that manages the increased complexity.
Solution Approach 2:
The dynamic element matching implementation includes feedback mechanisms that monitor circuit performance and adjust element assignments in real-time to compensate for non-linearity. This feedback-based approach improves reliability by continuously optimizing circuit operation, with the complexity managed through systematic feedback control rather than static complex circuit design.
3Measurement precision
If high frequency quantization noise is filtered before the amplifier stage, then noise performance is improved, but loss of energy increases
Solution Approach 1:
The reconstruction filter performs preliminary filtering of quantization noise before the signal reaches the amplifier stage. By removing high frequency noise components in advance, the filter prevents these noise components from being amplified, thereby improving signal fidelity while avoiding the energy waste that would occur if the amplifier had to process and then discard noisy signals.
Solution Approach 2:
The patent converts the potentially harmful effect of quantization noise by using the filtering process to transform noise-laden signals into clean signals before amplification. The filter exploits the frequency separation between signal and noise components to convert what would be wasted amplifier power processing noise into beneficial signal amplification, thereby improving energy efficiency despite the added filtering stage.
Data Source
AI summary
A digital to analog converter that includes a delta sigma modulator coupled to receive a digital data. The delta sigma modulator supplies a multi-bit resistor digital to analog converter (DAC). The multi-bit resistor digital to analog converter supplies an amplifier with an analog signal corresponding to the digital data. A first low pass filter is coupled between the multi-bit digital to analog converter and the amplifier stage and filters out shaped quantization noise before it reaches the amplifier. A second low pass filter is coupled to an output of the amplifier stage and filters out residual quantization noise and chopping artifacts from the amplifier stage.