Segmented Inductor Structure for Magnetic Field Cancellation
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Solution Overview
Problem
Inductors on silicon integrated circuits (ICs) face challenges due to magnetic field interference, which affects the operation of surrounding circuitry, particularly when inductors are closely positioned, leading to cross-coupling and noise issues, and existing designs like the figure-of-8 inductor only partially mitigate these problems.
Innovation Solution
The design of an inductor structure with an even number of segments, each with a loop and a crossover section that causes current to circulate in opposite rotational directions, resulting in increased cancellation of magnetic fields along specific axes, reducing interference and allowing for more compact chip designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If inductors are positioned closer together on the chip to minimize chip area, then chip area is reduced, but magnetic field interference and cross-coupling between inductors increases
Solution Approach 1:
The inductor is divided into multiple segments (at least three segments: first inductor segment, second inductor segment, and third inductor segment) arranged in a specific geometric pattern. Each segment generates a magnetic field, and the segmented arrangement allows for spatial distribution of magnetic field sources, enabling cancellation effects between adjacent segments while maintaining compact footprint on the chip.
Solution Approach 2:
The inductor segments are arranged in an asymmetric geometric pattern where the first and second inductor segments are oriented at a first angle to a reference axis, while the third inductor segment is oriented at a second angle (different from the first angle) to the reference axis. This asymmetric angular arrangement creates specific magnetic field cancellation patterns along particular axes, reducing interference in critical directions while maintaining overall compactness.
2Reliability
If traditional spiral inductor configuration is used, then inductor functionality is achieved, but magnetic field radiates uniformly in all directions causing interference to surrounding circuitry
Solution Approach 1:
The traditional spiral inductor is segmented into multiple discrete inductor segments arranged in a specific geometric configuration. This segmentation transforms the uniform omnidirectional magnetic field radiation of a traditional spiral inductor into a distributed pattern where magnetic fields from individual segments can cancel each other along specific axes, reducing overall interference while maintaining inductor functionality.
Solution Approach 2:
The inductor design implements directional magnetic field cancellation by orienting different segments at specific angles. The first and second segments are oriented at a first angle to a reference axis, while the third segment is oriented at a second angle, creating localized cancellation zones in specific directions. This allows the inductor to maintain its function while reducing magnetic field interference in critical surrounding areas.
3Object-generated harmful factors
If figure-of-8 inductor configuration is used, then some magnetic field cancellation is achieved along one axis, but residual magnetic field components remain in other directions
Solution Approach 1:
The inductor is divided into at least three segments arranged in a geometric pattern that generalizes the figure-of-8 concept. While a figure-of-8 has two lobes, this design uses three or more segments oriented at different angles to the reference axis, creating multiple cancellation axes and providing more comprehensive magnetic field suppression in multiple directions simultaneously.
Solution Approach 2:
The inductor segments are arranged with asymmetric angular orientations: the first and second inductor segments are oriented at a first angle to a reference axis, while the third inductor segment is oriented at a second angle (different from the first angle). This asymmetric multi-angle arrangement creates magnetic field cancellation along multiple different axes, extending the cancellation benefit beyond a single axis to cover broader angular ranges and reduce residual fields in more directions.
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 design significantly reduces magnetic field interference and cross-coupling effects, enabling more densely packed components on the chip while maintaining high inductance values, thus addressing the limitations of prior art inductor configurations.
Implementation Method 1
current flows around the structure in the directions indicated by the arrows. The current exits the inductor via a feed line 304 which exits the inductor in a plane perpendicular to the plane of the inductor. As a result of the crossover section in the middle of the figure-of-8 inductor, the current flows in a clockwise direction around the lower loop 306 of the inductor and in an anticlockwise direction around the upper loop 308 of the inductor.
Implementation Method 2
The magnetic field created by the current flowing clockwise around the lower loop is directed into the page and the magnetic field created by the current flowing anticlockwise around the upper loop is directed out of the page. The field lines join such that most of the magnetic field components in the plane of the inductor are contained within the area of the figure-of-8 structure. A degree of cancellation of the magnetic field components is thus achieved at distance from the inductor in the plane of the inductor.
Data Source
AI summary
An inductor structure includes an even number of segments, each segment adjacent to two segments, each segment including a loop, each loop having a first end and a second end; and a crossover section adjacent to each segment, the crossover section coupling each of the first ends and second ends of the loops so as to cause current to circulate around the loop of each segment in an opposite rotational direction to the direction of current circulation in the loops of the segments adjacent to that segment.