Leadframe Shunt Resistor Package With Temperature-Stable Current Sensing
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Solution Overview
Problem
Conventional current sense devices are large, complex, expensive, and inaccurate, with the Allego ACS711 current sensor being relatively expensive and exhibiting low accuracy.
Innovation Solution
An IC current sense package with an integrated shunt resistor, an IC die including current sense circuitry, and a mold encapsulation, formed as a flat, no leads package, featuring a temperature compensation resistor with a similar temperature coefficient of resistance as the shunt resistor, and a partial leadframe with externally contactable shunt resistor contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sense devices are used, then current sensing function is provided, but the devices are large, complex, expensive, and inaccurate
Solution Approach 1:
The patent combines the shunt resistor and current sense circuitry into a single integrated IC package. The shunt resistor is formed as part of the leadframe structure, and the current sense circuitry is integrated on an IC die that is mounted on the leadframe. This merging eliminates the need for separate discrete components, reducing overall device complexity while maintaining accurate current sensing functionality.
Solution Approach 2:
The leadframe structure serves multiple functions: it provides mechanical support, acts as the shunt resistor for current measurement, and serves as the package substrate for mounting the IC die. This multi-functionality reduces the number of separate components needed, simplifying the overall device structure while achieving accurate current sensing.
2Measurement precision
If conventional current sense devices are used, then current sensing function is provided, but the devices are large and expensive
Solution Approach 1:
The integration of the shunt resistor and current sense circuitry into a single compact IC package dramatically reduces the overall size. The shunt resistor is formed as a thin trace on the leadframe, and the IC die is mounted directly on the leadframe, eliminating the need for large discrete components and reducing the total package footprint.
Solution Approach 2:
The IC die is mounted on top of the leadframe structure, with the shunt resistor trace integrated into the leadframe itself. The mold encapsulation then encloses both the leadframe and IC die, creating a nested configuration where smaller components are integrated within the structure of larger components, maximizing space efficiency.
3Measurement precision
If temperature compensation is implemented, then accuracy over temperature range is improved, but device complexity increases
Solution Approach 1:
The patent implements temperature compensation by selecting a temperature compensation resistor with a specific temperature coefficient that matches the shunt resistor's temperature coefficient. This localized matching of temperature characteristics compensates for temperature-induced resistance changes in the shunt resistor, maintaining measurement accuracy across temperature ranges without requiring complex compensation circuits.
Solution Approach 2:
The temperature compensation mechanism works by utilizing the temperature coefficient of resistance of the compensation resistor to counteract the temperature-induced resistance changes in the shunt resistor. By carefully selecting the temperature coefficient parameter of the compensation resistor, the system maintains stable current sensing accuracy across varying temperatures without adding complex control logic.
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 solution provides a compact, accurate, and cost-effective current sense package with high accuracy, suitable for a wide range of operating temperatures, achieving at least 95% accuracy over -50°C to +125°C.
Implementation Method 1
an integrated shunt resistor... current sense circuitry to sense a current through the shunt resistor
Implementation Method 2
a temperature compensation resistor having a same or similar temperature coefficient of resistance (TCR) as the integrated shunt resistor
Data Source
AI summary
An integrated circuit (IC) package includes a partial leadframe including (a) a shunt resistor leadframe element including a pair of shunt resistor contacts and a shunt resistor conductively connected between the pair of shunt resistor contacts and (b) at least one external contact leadframe element separate from the shunt resistor leadframe element, the at least one external contact leadframe element allowing external contact to the IC package. The IC package also a mold encapsulation formed over the shunt resistor leadframe element, wherein the pair of shunt resistor contacts are externally contactable through the mold encapsulation.