Shielded Differential Inductor With Finger Structures
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Solution Overview
Problem
Analog and mixed signal integrated circuits face interference issues due to magnetic coupling, which causes frequency spurs and noise from components on or off the semiconductor substrate, affecting the performance of other components.
Innovation Solution
A shielded differential inductor design is implemented, featuring finger structures extending beyond the inductor's width orthogonal to current flow, connected to a ground connection, which isolates the electrical field and reduces substrate current loss, thereby attenuating frequency spurs and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a traditional inductor design is used without shielding, then the device complexity is low, but frequency spurs and noise are generated due to magnetic coupling
Solution Approach 1:
The shield is segmented into multiple finger structures arranged in parallel, each connected to ground. This segmentation allows the shield to effectively block magnetic coupling while maintaining a compact layout and reducing overall complexity compared to a solid shield structure.
Solution Approach 2:
The finger structures act as intermediary elements between the inductor and the substrate, providing a ground reference that blocks magnetic coupling paths without requiring direct contact with the inductor, thus reducing complexity while maintaining shielding effectiveness.
2Loss of energy
If the finger structures extend only within the inductor width, then the shielding area is minimized, but substrate current loss increases
Solution Approach 1:
The finger structures extend beyond the inductor width in specific directions (orthogonal to current flow) where magnetic coupling and substrate current loss are most significant, providing localized shielding where needed most while minimizing overall shield area and associated energy losses.
3Reliability
If the inductor size is increased to improve performance, then the inductance value increases, but the shielding effectiveness is compromised
Solution Approach 1:
The shield structures extend in a dimension orthogonal to the primary current flow direction, creating a three-dimensional shielding arrangement that effectively blocks magnetic coupling paths regardless of the inductor's planar size, thus maintaining shielding effectiveness as inductor size increases.
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
The solution effectively minimizes frequency spurs and noise, improves the quality factor of the inductor, and allows for adjustable inductor size without compromising shielding benefits, reducing substrate current loss and eddy current loss.
Implementation Method 1
finger structures extending beyond the inductor's width orthogonal to current flow, connected to a ground connection, which isolates the electrical field
Implementation Method 2
interference may originate in components on the substrate or components in proximity to the substrate and may take the form of frequency spurs or noise. The received interference may transfer to the other components through magnetic coupling
Implementation Method 3
reducing substrate current loss and eddy current loss
Data Source
AI summary
A shielded differential inductor forms a high quality factor (high-Q) inductor that is configured to attenuate frequency spurs and/or noise from magnetic coupling generated by electrical structures on or off of a substrate as well as interference received by other components from magnetic coupling generated by the inductor. The shielded differential inductor includes a differential inductor and a shield that substantially isolates the electrical field between the inductor and the substrate to reduce substrate current loss. The shield includes sets of finger structures that extend beyond the width of the inductor and a hub and spoke configuration of ground conductors that connect the sets of finger structures to ground.