The STEF01 device from STMicroelectronics is a universal integrated programmable electronic fuse optimized for monitoring output current and the input voltage on DC power lines. Sustaining up to 4A continuous current over a wide operating input-voltage range of 8V to 48V, with low insertion loss thanks to its integrated low-RDS(ON) MOSFET, the STEF01 programmable electronic fuse (E-fuse ) from STMicroelectronics extends the benefits of fast-acting overload protection to applications at higher power ratings.
When connected in series to the main power rail, the STEF01 device 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.
The device is fully programmable, parameters including UVLO, overvoltage clamp and start-up time can be set by means of external components. The adjustable turn-on time feature of the STEF01 device is useful for keeping the in-rush current under control during start-up and hot-swap operations. The device can provide either thermal latch or auto-retry protection modes, which are selectable by means of a dedicated pin.
The STEF01 also provides a gate driver pin for an external power MOSFET to implement a reverse-current blocking circuit. The intervention of the thermal protection is signalled to the board monitoring circuits through a signal on the fault pin.
Key Benefits of Electronic Fuses
Unlike conventional fuses, which are based on the principle that a conductor will overheat and melt during an overload condition, the STMicroelectronics eFuse only clamps the output voltage and/or limits the throughput current, thus allowing the device to be supplied correctly, before eventually disconnecting the load in case of persistent failure. This quick and intelligent response to faults prevents load and supply damage from occurring and avoids false triggering caused by transient conditions. Moreover, in applications powered by DC buses, eFuses reduce the bus droop due to faulty loads, avoiding the propagation of nuisance or undervoltage to other loads connected to the same bus.
Since eFuses are resettable devices, they can immediately be reset with a signal from the system by either cycling the supply power or by simply waiting, if auto-retry is used. The equipment’s uptime is maximized and the cost and complexity of maintenance are reduced. In some applications, inrush current conditions can occur during start-up or hot-plugging leading to nuisance blowing of traditional fuses. STMicroelectronics eFuses are able to prevent this by ramping the output voltage up in a controlled manner to prevent large inrush currents from overloading the power supply. This feature is crucial when multiple loads are supplied by a single power supply. Every eFuse can be programmed and tailored to the specific needs of the application with most eFuses allowing users to set the current limit and start-up time for flexible application design. The undervoltage lockout and output clamp levels as well as the device’s operating mode (latch-off or auto-retry mode) can also be configured on certain part numbers.
The evaluation board has the STEF01 E-fuse with integrated control circuit and a low on-resistance MOSFET switch and provides a full set of protections, including overcurrent, overvoltage and inrush current. Designers can adjust UVLO threshold, clamping voltage and overload current limits through mechanical trimmers on the evaluation board.. The STEVAL-EFUSE01 evaluation board lets designers easily adjust the output voltage ramp rate at the desired start-up time, by changing the Cdv/dt capacitor. As most applications require a flag to signal that the output voltage is in the correct range, the STEVAL-EFUSE01 also features a PG test point for information about the voltage drop on the pass element. The STEVAL-EFUSE01 also features thermal latch and auto-retry thermal protection modes, selectable through a dedicated jumper configuration.
The STEF01 E-fuse can be used to replace traditional circuit protection fuses in a wide range of applications including Industrial Control Equipment, Lighting, HVAC, Building Automation, Communications and Power Supplies.
Key Features & Specifications
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Click here to download the STEF01 datasheet.
Click here to download the STEVAL-EFUSE01 Evaluation Board databrief.
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