High-Power Electronic Fuse with Value-Added Features for Safety and Reliability

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STMicroelectronics has introduced STEF01 a universal integrated electronic fuse optimized for monitoring output current and the input voltage on DC power lines. When connected in series to the main power rail, it is able to detect and react to overcurrent and overvoltage conditions. When an overload condition occurs, the device limits the output current to a safe value defined by the user. If the anomalous overload condition persists, the device goes into an open state, disconnecting the load from the power supply.

Lower Voltage Ramp-up Time

The STEF01 leverages ST’s BCD8 high-voltage process to integrate value-added features, including dV/dt control to prevent excessive inrush current during startup or hot-swap insertion. This slows the output-voltage ramp-up time to at least three ms, which can be increased if desired by connecting an external capacitor. Programmable Under-Voltage Lockout (UVLO), also set using external components, allows the user to fine-tune the desired voltage-rail minimum value to suit the load requirements.

Thermal shutdown with latching

Further features include thermal shutdown with latching or auto-retry, and maximum dissipated-power protection, which each prevent exceptionally high power from damaging the STEF01 when starting up into heavy capacitive loads, or during large load transients or short-circuits at high voltage. There is also a power-good indicator, and an enable/fault pin that can be used as either a status monitor or to control the device. A dedicated gate-driver output for controlling an external N-channel MOSFET simplifies implementation of reverse-current protection.

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The device is fully programmable. UVLO, over voltage clamp and start-up time can be set by means of external components. The adjustable turn-on time is useful to keep the in-rush current under control during startup and hot-swap operations. The device provides either thermal latch and auto-retry protection modes, which are selectable by means of a dedicated pin.

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The STEF01 provides a gate driver pin for an external power MOSFET to implement a reverse-current blocking circuit. The intervention of the thermal protection is signaled to the board monitoring circuits through a signal on the fault pin.

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