Cross-Coupled Bondwire Traces for Inductance Reduction
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Solution Overview
Problem
Conventional methods for reducing parasitic inductance in integrated circuits, such as parallel bonding of traces, often fail to effectively lower inductance due to increased magnetic coupling, making wideband applications challenging, especially at high frequencies.
Innovation Solution
The approach involves cross-coupling differential bondwire traces with opposite polarities to reduce inductance, utilizing the magnetic coupling factor K to cancel out adjacent magnetic fields and minimize effective inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If multiple bondwires or traces are connected in parallel to reduce inductance, then the effective inductance decreases, but the magnetic coupling factor K increases causing the inductance reduction to be insufficient
Solution Approach 1:
The patent inverts the conventional parallel connection approach by using cross-coupling connections between differential pairs. Instead of directly paralleling traces to reduce inductance, the invention connects traces in a cross pattern where trace L1 connects to both P1 and P3, trace L2 connects to both P2 and P4, and so on. This inversion of the connection topology allows the magnetic coupling to work in favor of reducing inductance rather than opposing it, achieving better inductance reduction effectiveness.
Solution Approach 2:
The patent changes the connection configuration parameter from conventional parallel to cross-coupled parallel. By modifying how the traces are interconnected - specifically making each trace connect to both differential inputs and outputs in a crossed pattern - the magnetic coupling factor K is transformed from a harmful element to a beneficial one that further reduces the effective inductance of the differential signal path.
2Ease of manufacture
If conventional parallel bondwire connection is used, then manufacturing is simpler, but magnetic fields strengthen each other increasing effective inductance
Solution Approach 1:
The patent applies the inversion principle by reversing the conventional parallel connection approach. Instead of connecting bondwires in simple parallel where magnetic fields reinforce each other, the invention uses cross-coupling connections where the magnetic fields of adjacent traces oppose each other, thereby reducing the effective inductance while maintaining differential signal integrity.
Solution Approach 2:
The patent converts the harmful magnetic coupling effect into a beneficial one. By using cross-coupled connections, the magnetic fields that would normally strengthen each other and increase inductance are instead configured to cancel each other out, reducing the effective inductance. This transforms the previously harmful magnetic interaction into a useful mechanism for inductance reduction.
3Device complexity
If parallel traces are used to reduce inductance, then the structure is simpler, but magnetic coupling reduces the effectiveness of inductance reduction
Solution Approach 1:
The patent inverts the conventional parallel trace configuration by implementing cross-coupling connections. Instead of simple parallel traces where each trace connects to corresponding points, the invention crosses the connections so that traces interconnect between differential inputs and outputs in a pattern that utilizes magnetic coupling to reduce inductance effectively.
Solution Approach 2:
The patent changes the topological parameter of the trace configuration from conventional parallel to cross-coupled parallel. This parameter change in the connection topology transforms the magnetic coupling effect from detrimental to beneficial, achieving superior inductance reduction while maintaining reasonable structural 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 method significantly reduces parasitic inductance, as demonstrated by simulation results, improving wideband matching and reducing sensitivity to component variations, particularly in power amplifier output matching applications.
Implementation Method 1
the bondwire/trace magnetic coupling factor K can be used to reduce the line inductance
Implementation Method 2
the bondwire traces with opposite polarities to reduce inductance, utilizing the magnetic coupling factor K to cancel out adjacent magnetic fields
Data Source
AI summary
A method and system for reducing the inductance on an integrated circuit. The method and system comprises providing a first differential line, including a first input and a first output, the first differential line including at least two bondwire traces which are coupled in parallel. The method and system also comprises providing a second differential line including a second input and a second output, the second differential line including at least two bondwire traces which are coupled in parallel, the first differential line being of opposite polarity to the second differential line. The method and system further comprises cross-coupling of the first input with the second input and the first output with the second output to reduce the inductance caused by bondwire traces. A technique in accordance with the invention uses the coupling factor K to help to further reduce the inductance. By changing the input ordering of differential bondwires/traces, the bondwire/trace magnetic coupling factor K can be used to reduce the line inductance.