Electronic fuse protects systems from power gone rogue

By Warren Miller, contributing writer

STMicroelectronics recently announced the addition of the STEF01 electronic fuse to its product line. The STEF01 is a universally integrated, fully programmable solution for monitoring input voltage and output current on DC power lines. With this new device, ST extends fast-acting overload protection to applications at higher power ratings.

The STEF01 can sustain up to 4-A continuous current over an operating input voltage range of 8 V to 48 V with low insertion loss due to its integrated low-RDS(ON) VIPower MOSFET. The maximum input voltage is 55 V. The device’s output clamp voltage is adjustable from anywhere between 10 V to 52 V, and it operates at a junction temperature between –40°C and 125°C.

The STEF01 works by detecting and reacting to overcurrent/overvoltage conditions by limiting the output current to a predetermined value programmed by the user. The device will then disconnect from the power supply and go into an open state if the overload condition isn’t otherwise dealt with. A dedicated pin allows the user to enable auto-retry protection and thermal latch modes, making the device well suited to controlling the in-rush current while startup and hot-swap operations are underway.

The STEF01 also implements a built-in gate driver pin to enable a reverse-current blocking circuit, which signals to the board monitoring circuits that thermal protection has been enabled via a signal on the fault pin.

Most systems must react differently to rogue power deviations, so the programmable capabilities of the STEF01 make it possible to adjust the behavior of the device based on the requirements of the system. The UVLO (undervoltage lockout) input, for example (shown at the bottom of the STEF01 block diagram), can be used to adjust the threshold used for undervoltage detection. Simply add a couple of external resistors and the default 14.5-V threshold can be adjusted from between 8 V and 45 V.

Similarly, the dv/dt input can be used to adjust the slew rate of the output voltage turn-on. The internal capacitor allows a ramp-up time of about 3 ms. An external capacitor can be added to this pin to increase the ramp-up time. Other pins allow changes to thermal protection behavior, overvoltage clamp level, and overload current limit level. Outputs help signal the behavior of the device and can flag thermal faults or power good operation.

Block diagram of the STEF01. Image source: ST Microelectronics.

The STEF01 is designed to provide easy-to-use protection for a variety of potential applications, including circuit breakers, industrial hot-swap boards, and power buses and/or modules for everything from telecom equipment to security systems.

Available now, the STEF01, housed in a 14-pin package, is priced from $1.00 in quantities of 1,000. Click here to download the datasheet, order samples, or purchase.