STEF05: When over-current occurs, what is the minimum time for the device to "open".

[Peter BENSCH]

The STEF05 is not a conventional fuse, but an electronic one, so it reacts immidiately, i.e. really fast. Definitely faster than the output capacitor can discharge.

But you should also keep in mind that it also not "opens" like a conventional fuse, but rather limits the output current (see datasheet, 5.1.4).

Does it answer your question?

/Peter

[RBerw.1]

According to the data sheet: If the anomalous overload persists, the STEF05 goes into an "open state", disconnecting the load from the power supply. I'm assuming this is different then thermal shutdown (it's not clear to me what would occur first).

How quickly does the open state occur?

How does the device recover from the open state?

[Peter BENSCH]

At overload the STEF05 limits the output current at the value determined by the external resistor.

When the anomalous overload condition persists, it creates some power dissipation depending on the limited current, which might increase the chip temperature. If that temperature exceeds the threshold the thermal shutdown disables the internal power MOSFET, which then disconnects the load. Please have a look at the datasheet, section 5.1.5 (pg. 9) describing that feature and the recover process using Power On Reset or pulling EN pin low.

So 1st the current gets limited, 2nd a thermal shutdown might occur. The time till shutdown heavily depends on load conditions, the ambient temperature and the power dissipation within the chip, i.e. mainly on the current limit set with the external resistor.

Best regards,

/Peter

[RBerw.1]

Hello Peter,

I need your help once more: "How does the device recover from the open state?

Regards.

[Peter BENSCH]

The answer is also mentioned in the same section 5.1.5 mentioned above:

"If the device temperature exceeds the thermal latch threshold, typically 165 °C, the thermal shutdown circuitry turns the power MOSFET off, thus disconnecting the load. The EN/Fault pin of the device is automatically set at an intermediate voltage, in order to signal the overtemperature event. In this condition the E-fuse can be reset either by cycling the supply voltage or by pulling down the EN pin below the Vil threshold and then releasing it."

/Peter