STEF01 Universal Electronic Fuse STMicroelectronics STEF01 Universal Electronic Fuse is optimized for monitoring output current and the input voltage on DC power lines. The STEF01 is able to detect and react to overcurrent and overvoltage conditions when connected in series to the main power rail. When an overload condition occurs, the device limits the output current to a user-defined safe value. If the anomalous overload condition persists, the device goes into an open state, disconnecting the load from the power supply.