On-Die Spiral Air-Core Inductor Layout for Low-Resistance PMICs
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Solution Overview
Problem
Existing Power Management Integrated Circuits (PMICs) with integrated inductors face inefficiencies due to additional routing metal required for connecting solenoid and stripline designs, leading to increased resistance and reduced quality factor, which affects efficiency and electromagnetic interference.
Innovation Solution
A PMIC with a spiral air-core inductor design featuring a gap at its center, eliminating the need for additional metal routing and placing supply connection pads within the gap to minimize parasitic resistance and electromagnetic interference, while using a magnetic core wrapping the windings for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solenoid or stripline inductor designs are used, then inductance is achieved, but additional routing metal is required which increases resistance and lowers quality factor
Solution Approach 1:
The patent transitions from planar routing (2D metal paths on surface) to a 3D vertical integration where the spiral inductor is formed directly over the PMIC die. The connection pads are positioned at the center of the spiral, allowing direct vertical connections through vias without requiring additional lateral routing metal, thus reducing resistance while maintaining inductance.
Solution Approach 2:
The patent merges the inductor structure with the PMIC by integrating the spiral inductor directly on top of the PMIC die. The connection pads of the inductor are combined with the PMIC's supply connection pads at the center, eliminating the need for separate routing paths and reducing overall resistance.
2Ease of operation
If additional routing metal is added to connect solenoid/stripline pads, then connectivity is achieved, but device complexity and EMI increase
Solution Approach 1:
The patent extracts the connection pads from the periphery and places them at the center of the spiral inductor. This central positioning allows the pads to be directly integrated with the PMIC's existing connection pads, eliminating the need for additional routing metal and reducing device complexity.
3Ease of manufacture
If connection pads are placed at opposite ends of device, then inductor structure is simplified, but additional routing metal is required
Solution Approach 1:
The patent uses a symmetric spiral structure with asymmetric pad placement - while the spiral itself is symmetric, the connection pads are positioned at the center rather than at opposite ends. This asymmetric placement optimizes the connection by allowing direct vertical routing to the PMIC, eliminating lateral routing resistance.
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 reduces inductor resistance by 30-50% and improves the quality factor, leading to lower electromagnetic interference and increased efficiency by minimizing parasitic interconnects and optimizing inductance.
Implementation Method 1
In various embodiments the on-die inductor may have a magnetic core wrapping the windings
Data Source
AI summary
A single/Multi-phase PMIC built on silicon substrate with coil layers processed on top of the PMIC layers' is provided. The integrated coil is in a spiral form, with a gap at the center of the coil, making additional metal routing not required. The integrated coil has connection pads located in the center gap of the spiral form, limiting the overall inductor resistance to the device only. The on-die inductor may have a magnetic core wrapping the windings. The spiral form may be implemented in a circular design, or a racetrack (elongated spiral) design. The coil layers may be implemented as multiple coil layers or as a single coil layer, connected in parallel (with the same I/O pads), reducing the resistance and maintaining the inductance.