Multi-Bit DAC Element Rotation for Mismatch Noise Reduction
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Solution Overview
Problem
Multi-bit delta/sigma modulators in digital-to-analog converters face challenges due to differences in nominally identical circuit elements caused by fabrication variations, leading to nonlinear distortion and spectral noise.
Innovation Solution
A multi-bit data weighted averaging circuit with a thermometer encoder and rotational dynamic element matching circuit is implemented, using a binary to thermometer code conversion array to select and rotate DAC elements, ensuring identical long-term usage and minimizing mismatch errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional analog-to-digital and digital-to-analog conversion techniques are used with low sampling rates, then the conversion can be implemented with simpler digital processing, but very precise analog components are required which increases manufacturing complexity and cost
Solution Approach 1:
The patent changes the sampling rate parameter from Nyquist rate to oversampling rate (higher frequency), which transforms the conversion approach from requiring precise analog components to using simple high-tolerance components with complex digital signal processing for filtering aliasing frequencies
Solution Approach 2:
The patent implements dynamic element matching that dynamically selects and rotates DAC elements based on measured mismatch characteristics, adapting the conversion process to compensate for component variations rather than relying on fixed precise components
2Measurement precision
If oversampling is used with simple high-tolerance components, then high resolution can be achieved, but fast and complex digital signal processing is required to filter aliasing frequencies
Solution Approach 1:
The patent uses dynamic element matching with rotational rotation of DAC elements that adapts to mismatch characteristics, providing high resolution conversion while managing digital processing complexity through intelligent element selection rather than brute-force filtering
3Reliability
If dynamic element matching is implemented to compensate for fabrication variations, then nonlinear distortion and spectral noise are reduced, but the device complexity increases due to additional rotation and selection circuits
Solution Approach 1:
The patent implements dynamic element matching with rotational rotation of DAC elements based on measured mismatch characteristics, dynamically selecting elements to compensate for fabrication variations and reduce distortion while managing complexity through adaptive selection
Solution Approach 2:
The patent measures mismatch characteristics of DAC elements and uses this feedback information to dynamically rotate and select elements, creating a closed-loop system that compensates for fabrication variations and improves linearity performance
4Quantity of substance
If multi-bit DAC elements are used instead of single-bit elements, then the number of elements required is reduced, but mismatch errors between elements become more significant due to greater nominal value differences
Solution Approach 1:
The patent implements dynamic element matching with rotational rotation that adapts to mismatch characteristics of multi-bit DAC elements, dynamically selecting and rotating elements to compensate for greater nominal value differences while maintaining accuracy
Solution Approach 2:
The patent changes from single-bit to multi-bit DAC elements, reducing the number of elements required while using dynamic element matching to compensate for the greater mismatch errors inherent in multi-bit elements with larger nominal value differences
Data Source
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AI summary
A multi-level data weighted averaging circuit for inclusion in a multi-bit DAC circuit has a thermometer encoder that includes a binary to thermometer code conversion array configured for retaining or generating a multi-bit code representing an amplitude to be developed by each of the DAC element of the DAC circuit. The thermometer encoder is in communication with a multi-bit delta/sigma modulator to receive an oversampled binary coding representing an amplitude of a sampling of an analog signal. The oversampled binary coding is applied to an element selector to select the elements retaining or generating the element binary strings of bits of the multi-bit thermometer code. The multi-bit thermometer code is transferred to a rotational dynamic element matching circuit that rotationally selects order that the DAC elements are to receive each of the element binary strings of bits of the multi-bit thermometer code.