ST’s electronic fuse integrates “value-added” safety and reliability features

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.