DAC Dynamic Element Selection for Mismatch and THD Control
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Solution Overview
Problem
Digital-to-analog converters (DACs) face performance issues due to mismatches in circuit elements, which affect their dynamic specifications such as total harmonic distortion (THD) and signal-to-noise ratio (SNR), particularly in binary-weighted and equal-sized element configurations.
Innovation Solution
The implementation of a dynamic element matching (DEM) technique that dynamically selects circuit elements using a thermometer decoder and a signal mapping circuit, generating control signals based on fractional data weights to mitigate element mismatches and improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If binary-weighted circuit elements are used in a DAC, then the number of circuit elements is reduced, but the manufacturing precision and matching accuracy deteriorate due to the large size ratio between largest and smallest elements
Solution Approach 1:
The DAC is divided into multiple sub-DACs, each with a subset of circuit elements. This segmentation allows each sub-DAC to use fewer elements with better matching accuracy, while the overall DAC maintains the functionality of handling N-bit input data through coordinated operation of multiple sub-DACs.
Solution Approach 2:
The invention dynamically selects and switches between different subsets of circuit elements in different sub-DACs based on the input data. This dynamic element selection and switching mechanism allows the system to mitigate the effects of element mismatches while maintaining the benefits of reduced element count.
2Manufacturing precision
If equal-sized circuit elements are used in a DAC, then the manufacturing precision and matching accuracy improve, but the device complexity increases due to the larger number of elements required
Solution Approach 1:
The large set of equal-sized circuit elements is divided into multiple subsets assigned to different sub-DACs. This segmentation reduces the number of elements each sub-DAC must handle, simplifying the control logic and switching mechanisms while maintaining the overall accuracy benefits of using equal-sized elements.
Solution Approach 2:
The system dynamically selects which subset of equal-sized elements to activate based on the input data distribution. This dynamic selection optimizes the trade-off between matching accuracy and device complexity by activating only the necessary number of elements for each conversion operation.
3Reliability
If dynamic element matching techniques are implemented, then the dynamic performance and THD improve, but the device complexity increases due to additional control circuits and switching mechanisms
Solution Approach 1:
The control and switching functions are segmented and distributed across multiple sub-DACs rather than centralized. This distribution reduces the complexity burden on any single control circuit while achieving the overall dynamic performance improvements through coordinated operation of the segmented subsystems.
Data Source
AI summary
According to at least one embodiment of the invention, an apparatus may include first, second and third circuits. The first circuit receives input data and provides a plurality of first signals asserted based on the input data. The second circuit receives the plurality of first signals and provides a plurality of second signals used to select a plurality of circuit elements. The third circuit generates a control for the second circuit using a fractional data weight of the input data, the second circuit mapping the plurality of first signals to the plurality of second signals based on the control from the third circuit.