Geneva, Switzerland—If you are doing hot-swap design, fusing to prevent overcurrent damage is critical. The STEF05 and STEF12 electronic fuses from STMicroelectronics (5 and 12V ratings, respectively) can replace larger conventional fuses or other protection devices. Unlike fuses, however they do not cut the power suddenly, nor require replacement after actuating.
The 3×3mm devices restrict the supply current, thus protecting the connected circuitry, and ultimately turn the protected equipment off, if the fault persists. They can be reset by a signal from the system or by restarting the power supply. The devices provide a signal when they are intervening, allowing the system to generate a warning. If the fault persists after the reset, the fuse immediately limits the current and turns off again to protect the circuitry.
The devices also integrate circuitry which limits voltage fluctuations applied to the protected load, as well as programmable start-up time (via an external capacitor)—a function needed in hot-swap systems. The current limit is set via an external resistor.
Pricing, packaging, and availability: The STEF05 and STEF12 are in production now, in a 3×3mm DFN 10-lead package, and priced from $0.75 (1000 pieces).
For more information: contact STMicroelectronics at http://www.st.com.