This document introduces 5V and 12V power line protection based on STEF05 and STEF12 electronic fuses. These electronic fuses are designed to monitor the output current and input voltage and protect the electronic circuitry from overcurrent and overvoltage. They have programmable turn-on time to control the inrush current during startup and hot-swaps. When an overload condition occurs, the electronic fuse limits the output current to a predefined safe value. If the abnormal overload condition persists, it goes into an open state, disconnecting the load from the power supply. Both devices are equipped with a thermal protection circuit.