AN4069 Datasheet, PDF (1/16 Pages) STMicroelectronics – This demonstration board is based on the STEF05 and STEF12 electronic fuses

AN4069
Application note
5 V and 12 V power line protection based on STEF05 and STEF12
electronic fuses
Introduction
This demonstration board is based on the STEF05 and STEF12 electronic fuses (E-fuses).
It is designed to help developers to evaluate the benefit of the complete protection offered by
the E-fuse family and to customize their own application. The E-fuse family of hot-swap
converters is designed to replace the mechanical fuses on low voltage power lines.
The STEF05 and STEF12 are integrated electronic fuses optimized for monitoring the
output current and input voltage. Connected in series to the 5 V/12 V rails, they are capable
of protecting the electronic circuitry on their output from overcurrent and overvoltage.
The turn-on time is programmable by means of an external capacitor, allowing the control of
the inrush current at startup and during hot-swaps.
When an overload condition occurs, the E-fuse limits the output current to a predefined safe
value. If the anomalous overload condition persists, it goes into an open state, disconnecting
the load from the power supply. If a continuous short-circuit is present on the board, when
power is re-applied the E-fuse initially limits the output current to a safe value, and then
again goes into an open state. Both devices are equipped with a thermal protection circuit.
The intervention of thermal protection is signaled to the board monitoring circuits through a
signal on the ENABLE/FAULT pin that can be connected to other parts belonging to the
same family to cause a simultaneous shutdown during failure events.
Unlike mechanical fuses, which must be physically replaced after a single event, E-fuses do
not degrade in their performance after short-circuit/thermal protection interventions and can
be reset either by re-cycling the supply voltage or by using the ENABLE pin.
Figure 1. Board image
March 2012
Doc ID 022926 Rev 1
1/16
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