DAC Current Source Layout for Metal Fill Matching Precision
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Solution Overview
Problem
The challenge of circuit matching performance in digital-to-analog converters (DACs) is exacerbated by the need for strict metal filling density requirements, which can disrupt the weight proportional relationships of current source units, leading to mismatch errors and reduced precision.
Innovation Solution
Incorporating a metal filling strategy above both active and virtually connected current source units in the DAC, ensuring the metal filling areas align with the weight proportional relationships of these units to maintain precision and performance, while also meeting metal density requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If metal filling is performed above current source units to meet metal density requirements, then manufacturing compliance is improved, but non-uniform stress disrupts weight proportional relationships causing mismatch errors
Solution Approach 1:
The patent applies different metal filling strategies to different current source units based on their specific characteristics. Active current source units have metal filling configured to maintain weight proportional relationships, while dummy current source units have metal filling optimized for density compliance without affecting circuit function. This localized differentiation resolves the contradiction by allowing manufacturing compliance without compromising precision.
Solution Approach 2:
The current source array is segmented into active current source units and dummy current source units, each handling different aspects of the metal filling requirement. Active units maintain precision through controlled metal filling, while dummy units absorb excess metal density requirements. This segmentation allows the system to simultaneously satisfy both manufacturing compliance and precision requirements.
2Ease of manufacture
If metal filling area is increased to meet density requirements, then manufacturing compliance is improved, but stress uniformity deteriorates causing weight relationship disruption
Solution Approach 1:
Dummy current source units serve as intermediaries that absorb the metal filling density requirements without affecting the active current source units' weight proportional relationships. By placing dummy units strategically, the patent allows increased overall metal filling area for compliance while isolating the active units from stress-induced precision degradation.
3Device complexity
If metal filling is performed uniformly across all current source units, then manufacturing process simplicity is improved, but circuit matching performance deteriorates due to stress-induced weight errors
Solution Approach 1:
The patent implements location-dependent metal filling configurations where active current source units receive metal filling optimized for maintaining weight proportional relationships, while dummy current source units receive metal filling optimized for density compliance. This local quality differentiation improves precision without significantly increasing overall process complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces mismatch errors caused by non-uniform stress from high-layer thick metals, thereby improving circuit matching performance and precision of the DAC.
Implementation Method 1
the metal may generate stress on transistors on the active current source units
Data Source
AI summary
Embodiments of this application provide example digital-to-analog converters and electronic devices, and relate to the field of electronic technologies. The digital-to-analog converter includes a current source array and a switch array, and the current source array includes a plurality of active current source units. A metal is filled above the plurality of active current source units. The switch array includes a plurality of switch units. Control ends of the plurality of switch units are configured to receive control signals, and input ends of the plurality of switch units are respectively configured to receive corresponding currents provided by the plurality of active current source units. Output ends of the plurality of switch units are coupled to an output end of the digital-to-analog converter, and are configured to output analog signals.