Electronic fuse provides resettable electrical protection for 12 V power systems

The STEF12S electronic fuse from STMicroelectronics provides comprehensive protection against over-currents, over-voltages and under-voltages, as well as offering optional reverse-current blocking.

The STEF12S from STMicroelectronics is an electronic fuse which provides over-current protection to high-power equipment operating from a 12 V dc power line. 

Connected in series to the main power rail, the STEF12S detects and reacts to over-current or over-voltage conditions. When an overload condition occurs, the electronic fuse limits the output current to a safe value defined by the designer. If the overload condition persists, the fuse goes into an open state, disconnecting the load from the power supply.

In case of an over-voltage on the input, the STEF12S regulates the output to a preset safe value. Under-voltage lockout protection prevents the load from malfunctioning, keeping the device off if the rail voltage is too low.

The STEF12S’s DFN10 package features a dedicated pin for controlling the gate voltage of an optional external N-channel MOSFET, which may be used to perform reverse-current blocking if the input voltage is lost. 

The turn-on time of the fuse is programmable, which helps the power-system designer to control inrush current during start-up or hot-swap operations. 

The electronic fuse is available in a latching version, the STEF12S, or with an auto-retry function, the STEF12SA. The STEF05S is a companion chip for use with 5 V power rails.

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