Comb-like Metal Electrode for Integrated Current Sensing

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Solution Overview

Problem

Existing power devices with integrated sensing resistors face challenges such as significant silicon area occupation and precision requirements for trimming, leading to potential errors in current sensing and feedback control due to modified bias conditions.

Innovation Solution

The integration of a comb-like metal strip structure for the source or emitter electrode, where the sensing resistor is a portion of the metal strip, reducing silicon area usage and maintaining unbiased bias conditions, with a pre-established resistance value between connection pads, allowing precise voltage drop measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an integrated sensing resistor is connected in series with the sensing transistor, then current sensing capability is improved, but silicon area consumption increases significantly

Engineering Contradiction:

Improvecurrent sensing capabilityVSAvoidsilicon area consumption

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The sensing resistor is merged with the source or emitter electrode structure by forming a portion of the metal strip as the sensing resistor. This integration eliminates the need for separate sensing resistor components and their associated trimming circuits, significantly reducing silicon area while maintaining current sensing capability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The metal strip serving as the source or emitter electrode is given dual functionality: it acts as both the current conduction path and the sensing resistor. This multi-functional design allows the same structure to perform both power delivery and current measurement functions, reducing overall device complexity and area.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If trimming techniques are used to determine sensing resistance value, then measurement precision is improved, but device complexity and manufacturing steps increase

Engineering Contradiction:

Improvesensing resistance precisionVSAvoidtrimming circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The sensing resistor value is determined inherently by the physical dimensions and material properties of the metal strip during standard fabrication processes. The structure serves itself by using the electrode's own geometry (length, width, thickness) to define the resistance value, eliminating the need for external trimming circuits, fuses, or additional manufacturing steps.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The sensing resistance value is controlled by changing the geometric parameters of the metal strip (such as length, width, or thickness) during fabrication. This allows precise resistance values to be achieved through standard photolithography and deposition processes without requiring complex post-fabrication trimming operations.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If a sensing resistor is integrated into the power device structure, then current measurement accuracy is improved, but bias conditions of the transistor are altered

Engineering Contradiction:

Improvecurrent measurement accuracyVSAvoidbias condition stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

By merging the sensing resistor with the source or emitter electrode, the resistor becomes an intrinsic part of the transistor's current path rather than an external component. This integration ensures that the sensing resistor and transistor operate as a unified structure with consistent electrical characteristics across all operating conditions, maintaining stable bias conditions.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The sensing resistor is formed from the same metal material and fabrication process as the source or emitter electrode, ensuring homogeneous material properties and thermal expansion characteristics. This homogeneity ensures that the sensing resistor and transistor respond uniformly to temperature changes and electrical stress, maintaining stable bias conditions across varying operating environments.

Inventive Principle:

Principle #33Homogeneity

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 approach reduces silicon area consumption, maintains accurate bias conditions, and enables precise current sensing without altering the transistor's bias, improving feedback control and reducing errors in current measurement.

Implementation Method 1

a generated voltage drop, detectable by a control circuit, is proportional to the current that the power device delivers to a load

Methodology Applied

Scientific EffectOhm's Law: Ohm's Law

Data Source

PatentUS8299579B2Method for generating a signal representative of the current delivered to a load by a power device and relative power device

Publication Date: 2012.10.30 STMICROELECTRONICS SRL

AI summary

An integrated power transistor includes emitter or source regions, and a comb-like patterned metal electrode structure interconnecting the emitter or source regions and defining at least one connection pad. The comb-like patterned metal electrode structure includes a plurality of fingers. A current sensing resistor produces a voltage drop representative of a current delivered to a load by the integrated power transistor. The current sensing resistor includes a portion of a current carrying metal track having a known resistance value and extending between one of the fingers and a connectable point along the current carrying metal track.