Sense Transistor Source Electrode Segmentation for Current Accuracy
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Solution Overview
Problem
Current sensing circuits using sense transistors face challenges in maintaining strict proportionality between load and sense currents due to undesired side effects and interactions, particularly when the transistors do not operate at the same operating point, leading to inhomogeneous drain current flow and distortion in the proportional relationship.
Innovation Solution
A semiconductor device design with a separate source electrode for the sense transistor, electrically isolated from the power transistor, and a shared source electrode that covers both transistors, ensuring equal operating points and minimizing disturbances in current flow through the use of a control circuit and optimized metallization layers to maintain proportional current sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate source electrode is used for the sense transistor to improve current sensing accuracy, then measurement precision is improved, but device complexity increases due to additional electrode structures and isolation requirements
Solution Approach 1:
The source electrode structure is segmented into a first source electrode for the sense transistor and a second source electrode for the power transistor. This segmentation allows independent electrical connection and isolation, enabling accurate current sensing in the sense transistor without interference from the power transistor, while maintaining manageable structural complexity through clear functional division
Solution Approach 2:
The sense transistor's source electrode is extracted and separated from the power transistor's source electrode structure. This extraction allows the sense transistor to have its own dedicated source connection, enabling precise current measurement while the power transistor connects to the second source electrode, thus improving measurement precision without requiring complete integration of both transistors into a single electrode structure
2Device complexity
If both transistors share a common source electrode to simplify device structure, then device complexity is reduced, but measurement precision deteriorates due to inhomogeneous drain current flow and internal transverse currents
Solution Approach 1:
The common source electrode is segmented into separate first and second source electrodes, with the first source electrode dedicated to the sense transistor and the second to the power transistor. This segmentation eliminates the inhomogeneous current flow and internal transverse currents that would occur with a shared electrode, thereby improving measurement precision while maintaining relatively simple device structure through the use of only two distinct electrode regions
Solution Approach 2:
Different source electrode configurations are applied to different transistors: the sense transistor receives a dedicated first source electrode optimized for precise current measurement, while the power transistor connects to a second source electrode optimized for power handling. This local quality differentiation ensures each transistor operates in its optimal condition, improving overall measurement precision without requiring complex unified electrode structures
Data Source
AI summary
A semiconductor device a field of transistor cells integrated in a semiconductor body. A number of the transistor cells forming a power transistor and at least one of the transistor cells forming a sense transistor. A first source electrode is arranged on the semiconductor body electrically connected to the transistor cell(s) of the sense transistor but electrically isolated from the transistor cells of the power transistor. A second source electrode is arranged on the semiconductor body and covers the transistor cells of both the power transistor and the sense transistor, and at least partially covering the first source electrode in such a manner that the second source electrode is electrically connected only to the transistor cells of the power transistor but electrically isolated from the transistor cells of the sense transistor.