High-Side Current-Sense Measurement: Circuits and Principles

Abstract: This application note describes the use of current-sense amplifiers, differential amplifiers, and instrumentation amplifiers to measure battery charge and discharge currents in smartphones, tablets, computer notebooks, and USB accessories. It compares high-side current sense amplifiers with low-side differential amplifiers and recommends selection criteria for current-sense resistors. A high-voltage circuit breaker is described to provide system over-current protection due to faults and short circuits. Application circuits for a variable linear current source and a programmable 0–5A current source are included.