Thermometer DAC Cell Shifting for Harmonic Distortion Reduction
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Solution Overview
Problem
Thermometer encoded Digital-to-Analog Converter (DAC) architectures suffer from systematic errors leading to harmonic distortions due to non-identical DAC cells, which are not effectively addressed by existing technologies.
Innovation Solution
A DAC design that incorporates a shift code generation circuit to pseudorandomly shift the digital control code, reducing correlation between the input code and activated cells, thereby minimizing harmonic distortion and noise through a combination of code difference determination, pseudorandom binary sequences, and accumulator circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed cell selection is used for each digital code, then the DAC structure is simple, but systematic errors and harmonic distortions occur due to non-identical cells
Solution Approach 1:
The patent applies dynamics by making the cell selection variable rather than fixed. A random number generator continuously generates random values that are combined with the digital input code to dynamically select different subsets of DAC cells for each conversion cycle. This dynamic selection process ensures that no single non-identical cell is consistently activated, thereby randomizing and reducing systematic errors and harmonic distortions while maintaining structural simplicity
Solution Approach 2:
The patent changes the selection parameter of DAC cells from a fixed deterministic pattern to a randomized pattern. By introducing randomization into the cell selection process through combining random numbers with the digital code, the system alters which cells are activated without changing the physical DAC structure. This parameter change effectively reduces systematic errors caused by cell non-identical characteristics
2Manufacturing precision
If randomization techniques are applied to reduce harmonic distortion, then output accuracy improves, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary component - a random number generator and combination logic - that sits between the digital input code and the DAC cell selection process. This intermediary generates random values and combines them with the input code to produce the final cell selection pattern. By placing this intermediary layer, the system achieves randomization for error reduction without directly modifying the DAC cell structure, thus limiting the increase in device complexity to just the intermediary components
Data Source
AI summary
A digital-to-analog converter is provided. The digital-to-analog converter comprises an input configured to receiving a first digital control code for controlling a plurality of digital-to-analog converter cells. Further, the digital-to-analog converter comprises a code converter circuit configured to converter the first digital control code to a second digital control code. Further, the digital-to-analog converter comprises a shift code generation circuit configured to generate a shift code based on a code difference between the first digital control code and a third digital control code. The digital-to-analog converter additionally comprises a bit-shifter circuit configured to bit-shift the second digital control code based on the shift code in order to obtain a modified second digital control code. The digital-to-analog converter comprises a cell activation circuit configured to selectively activate one or more of the plurality of digital-to-analog converter cells based on the modified second digital control code. Each activated digital-to-analog converter cell is configured to output a respective cell output signal. Further, the digital-to-analog converter comprises an output configured to output an analog output signal based on the cell output signals.