DWA Circuit Rotation Scheme for DAC Tone Suppression
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Solution Overview
Problem
Existing DWA circuits for digital-analog conversion in audio applications suffer from tone generation due to mismatch in digital-analog conversion elements, leading to degradation in dynamic range and signal-to-noise ratio.
Innovation Solution
The proposed solution involves a DWA circuit configuration that includes a delay circuit, thermometer conversion unit, shift unit, arrangement conversion unit, and update unit, which processes the input digital signal to generate an output control code for an analog output circuit, effectively reducing tone generation by averaging the mismatch effects across multiple elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DWA circuit uses multiple digital-analog conversion elements, then signal-to-noise ratio is improved, but tone generation occurs due to element mismatch
Solution Approach 1:
The patent implements dynamic element matching by continuously rotating the assignment of digital-analog conversion elements to code positions. The rotation amount is dynamically adjusted based on the input signal level, making the system adaptive rather than static. This dynamic approach ensures that mismatch effects are averaged over time while maintaining optimal performance across different signal conditions.
Solution Approach 2:
The patent employs periodic rotation of element assignments through a rotation amount register that cycles through predetermined rotation values. This periodic action systematically varies which elements are assigned to which code positions, ensuring that mismatch effects are distributed and averaged over multiple rotation cycles, thereby reducing tone generation while maintaining noise shaping benefits.
2Reliability
If DWA circuit implements element averaging, then dynamic range is improved, but device complexity increases
Solution Approach 1:
The patent divides the DWA circuit into distinct functional modules: a rotation amount register storing predetermined rotation values, a rotation amount output unit, and an element assignment unit. This segmentation allows each module to perform a specific function independently, simplifying the overall design and making the complex averaging process more manageable and implementable.
Solution Approach 2:
The patent changes the parameter of rotation amount from a fixed value to a set of predetermined values stored in a register. By varying the rotation amount parameter systematically according to stored values, the circuit achieves complex averaging behavior through simple parameter variation rather than complex circuit logic, thereby reducing overall device complexity.
Data Source
AI summary
A DWA circuit includes: a thermometer conversion unit configured to convert an input digital signal into a thermometer code; a shift amount storage unit configured to store a shift amount; a shift unit configured to cyclically shift the thermometer code; an arrangement conversion unit configured to supply, to an analog output circuit, an output control code obtained by converting a bit arrangement of a shifted code; and an update unit configured to update the shift amount, in which the shifted code includes a plurality of unconverted bit fields, the output control code includes a plurality of converted bit fields, and the arrangement conversion unit is configured to perform arrangement conversions on a plurality of bits having a same position in a bit field in the plurality of unconverted bit fields, to arrange the plurality of bits in a same converted bit field among the plurality of converted bit fields.