1 Introduction

Current sense resistors are essential components in modern power systems, enabling precise monitoring of current flow. Traditionally, discrete shunt resistors are employed for this purpose, strategically placed in series with the load. However, in applications demanding high-current measurement, conventional shunt resistors exhibit limitations. As power dissipation scales proportionally with the square of the current, shunt resistors can become inefficient at higher currents, dissipating significant power otherwisest delivered to the load and necessitating larger, more robust resistor designs.

This application report details a novel approach to current sensing: utilizing a section of printed circuit board (PCB) copper trace as a shunt resistor. This technique offers potential benefits including reduced component count, lower parasitic inductance, and improved thermal management. However, challenges exist, including controlling trace thickness, accounting for the temperature coefficient of resistance, and minimizing current-induced resistance variations. Initial results demonstrated limitations related to trace thickness control and stability. Subsequent hardware revisions, notably Revision B, were designed to mitigate these issues and demonstrate the practicality of this approach. This report outlines the advantages and disadvantages of PCB trace current sensing, provides design considerations, and presents experimental findings from both initial and revised hardware implementations.