Segmented DAC Shuffling for ADC Linearity and Fast Conversion
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Solution Overview
Problem
Analog to digital converters (ADCs) and digital to analog converters (DACs) face challenges in achieving high linearity due to random variations during fabrication, leading to integral non-linearity errors, which affect the transfer characteristic and overall performance in applications requiring high resolution and throughput.
Innovation Solution
The implementation of a residue forming digital to analog converter with multiple cooperating DACs arranged in parallel, utilizing a data word generator that applies shuffling operations to improve linearity by equalizing the contribution of elements and reducing gain errors between main and sub-DAC parts, thereby enhancing the effective resolution and reducing integral non-linearity errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple cooperating DACs are arranged in parallel with shuffling operations, then linearity and effective resolution are improved, but device complexity increases
Solution Approach 1:
The DAC is divided into multiple cooperating digital to analog converters arranged in parallel, each handling portions of the data word. This segmentation allows independent optimization of each DAC unit while collectively achieving higher linearity through the combination of multiple units with shuffled element assignments.
Solution Approach 2:
The patent implements dynamic element matching through shuffling operations where the assignment of conversion elements to data bits changes based on measured element characteristics. This dynamic reassignment optimizes the transfer characteristic by compensating for fabrication variations, thereby improving linearity without requiring perfectly matched static elements.
2Manufacturing precision
If dynamic element matching with shuffling is implemented, then integral non-linearity errors are reduced, but data processing complexity increases
Solution Approach 1:
The system performs preliminary characterization of conversion elements during fabrication or initial operation, storing their individual weights or characteristics in lookup tables. This preliminary action enables subsequent shuffling operations to compensate for element variations without requiring complex real-time calculations during the actual conversion process.
Solution Approach 2:
The patent uses digital copies or representations of element characteristics (such as weight values stored in memory) to model the physical conversion elements. These digital models are shuffled and reassigned to create optimized transfer characteristics, avoiding the need to physically reconfigure the analog elements while still achieving dynamic element matching benefits.
3Manufacturing precision
If elements are sub-divided into multiple groups with weighted connections, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent assigns different weights to connections between element groups and the output node, creating local quality variations that compensate for fabrication tolerances. By optimizing the weight distribution in specific local regions of the DAC architecture, the system achieves improved overall linearity without requiring perfect uniformity across all elements.
Data Source
AI summary
A stage, suitable for use in and analog to digital converter or a digital to analog converter, comprises a plurality of slices. The slices can be operated together to form a composite output having reduced thermal noise, while each slice on its own has sufficiently small capacitance to respond quickly to changes in digital codes applied to the slice. This allows a fast conversion to be achieved without loss of noise performance. The slices can be sub-divided to reduce scaling mismatch between the most significant bit and the least significant bit. A shuffling scheme is implemented that allows shuffling to occur between the sub-sections of the slices without needing to implement a massively complex shuffler.