Notched Leadframe Current Sensor IC for Stable High-Frequency Sensing
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Solution Overview
Problem
Conventional magnetic field current sensors face challenges in high-speed current sensing due to skin effects, which affect signal magnitude and flatness over a wide range of input frequencies, and require complex conductor shapes to concentrate magnetic fields effectively.
Innovation Solution
A current sensor with a leadframe featuring notches in the throat region to concentrate magnetic fields on sensing elements, utilizing differential sensing with multiple magnetic field sensing elements positioned strategically to enhance signal quality and reduce charge movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current sensor designs are used, then the structure is simple, but skin effects cause signal magnitude and flatness degradation at high frequencies
Solution Approach 1:
The leadframe is segmented by introducing notches that divide the continuous conductor path into distinct sections. This segmentation concentrates the magnetic field in specific regions between the notches, improving signal consistency without requiring complex overall conductor shapes. The notches create localized high-field zones that enhance sensing while maintaining simple leadframe geometry.
Solution Approach 2:
The notches create local variations in the leadframe structure that concentrate magnetic flux density in specific sensing regions. By modifying only localized areas (the notch positions and shapes) rather than the entire conductor path, the design achieves improved signal consistency at high frequencies while keeping the overall device structure simple and manufacturable.
2Measurement precision
If notches are added to concentrate magnetic field, then signal consistency improves, but manufacturing complexity increases
Solution Approach 1:
The notch dimensions (width, depth, spacing) are optimized as key parameters to achieve effective magnetic field concentration. By carefully controlling these geometric parameters within practical manufacturing tolerances, the design achieves improved measurement precision while remaining compatible with standard leadframe fabrication processes. The parameters are chosen to balance performance gains with manufacturing ease.
3Speed
If feature size is reduced by notches, then skin effect frequency increases, but charge movement decreases
Solution Approach 1:
The notches introduce dimensional changes in the leadframe cross-section, creating narrower regions that increase the skin effect frequency. By modifying the geometric dimensions (reducing effective width at notch locations) rather than changing material properties or operating conditions, the design achieves improved frequency response while the reduced charge movement is acceptable given the enhanced sensing capability.
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 notched leadframe design increases signal consistency and reduces skin effect-induced fluctuations, providing a more stable and accurate magnetic field sensing performance across varying frequencies.
Implementation Method 1
conventional magnetic field current sensors sense current in a current-carrying conductor via a magnetic field generated by the current through the conductor
Implementation Method 2
the first magnetic field sensing element comprises a Hall effect element
Implementation Method 3
the first magnetic field sensing element comprises an MR element
Implementation Method 4
the first magnetic field sensing element comprises a TMR element
Data Source
AI summary
Methods and apparatus for a current sensor integrated circuit package that includes a die having a first magnetic field sensing element and a leadframe to support the die. The leadframe has a U-shaped current conductor loop with a throat region and a first notch in the throat region of the current conductor loop. A first magnetic field sensing element is positioned in relation to the first notch. In some embodiments, the first magnetic field sensing element is aligned with an edge of the first notch.