Asymmetric Stacked Inductor Reducing Parasitic Capacitance
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Solution Overview
Problem
Symmetrical differential inductors have high parasitic capacitance, leading to low self-resonance frequency and quality factor, limiting their application range.
Innovation Solution
The inductor device features a stacked structure with overlapping coils in perpendicular directions and non-overlapping crossing structures between metal layers, reducing equivalent parasitic capacitance and enhancing self-resonance frequency and quality factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a symmetrical differential inductor is used, then the structure is simple and easy to manufacture, but the parasitic capacitance is large resulting in low self-resonance frequency and low quality factor
Solution Approach 1:
The patent applies asymmetry by designing an asymmetric inductor structure where the first and second inductors have different geometries. Specifically, the first inductor has a different number of meander sections, different trace widths, or different spacing compared to the second inductor. This asymmetric configuration reduces the coupling between the two inductors, thereby reducing parasitic capacitance and improving the quality factor while maintaining manufacturability through standard PCB layout techniques.
2Ease of manufacture
If a symmetrical differential inductor is used, then the structure is simple and easy to manufacture, but the self-resonance frequency is low
Solution Approach 1:
The asymmetric design reduces parasitic capacitance between the differential signals, which directly increases the self-resonance frequency. By making the inductors asymmetric with different geometries or spacing, the coupling capacitance is minimized, allowing the inductor to operate at higher frequencies before reaching resonance, thus improving the speed parameter while keeping the structure manufacturable.
Solution Approach 2:
The patent employs three-dimensional stacking of multiple metal layers to increase the inductance value without increasing the planar footprint. By utilizing vertical stacking in the Z-dimension, the inductor achieves higher inductance through mutual inductance between layers, which allows for smaller physical dimensions while maintaining or improving the self-resonance frequency.
3Reliability
If overlapping coils in stacked structure are used, then the parasitic capacitance is reduced and self-resonance frequency is increased, but the device complexity increases
Solution Approach 1:
The patent utilizes vertical stacking across multiple metal layers to create overlapping coil structures. This three-dimensional arrangement reduces parasitic capacitance by separating the coils in the vertical dimension while maintaining compact planar footprint. The complexity is managed by using standard multi-layer PCB fabrication processes, making the increased structural complexity acceptable for achieving higher self-resonance frequency.
Data Source
AI summary
An inductor device includes a first winding, a second winding, a first connecting structure and a second connecting structure. The first winding includes a first coil and a second coil. The second winding includes a third coil and a fourth coil, the third coil is overlapped with the first coil, and the fourth coil is overlapped with the second coil. The first connecting structure includes a first crossing structure and a second crossing structure. The first crossing structure has a first crossing point and is configured to couple the first coil and the second coil. The second crossing structure has a second crossing point and is configured to couple the third coil and the fourth coil. The first crossing point is not overlapped with the second crossing point. The second connecting structure is configured to couple the second coil and the third coil.