Calculating Accuracy in High-Side Current-Sense Amplifiers (.PDF Download)

Recently, an engineer asked for a solution to provide high-side monitoring of a 20-A load with an accurate overcurrent detection threshold of better than 5%. No easily accessible off-the-shelf solutions offer the ability to use a low-value sense resistor with less than 5% accuracy, so why 5%? Would 10% be ok? For a 20-A load, a 10% current limit would cause the trip threshold to be 18 A (min) or 22 A (max), a much wider margin than would be acceptable. What are the factors involved that make 5% so difficult?...

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