Typical application

STEF033

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DocID025099 Rev 2

5.1.2

Normal operating condition

The STEF033 E-fuse behaves like a mechanical fuse, buffering the circuitry on its output

with the same voltage shown at its input, with a small voltage fall due to the N-channel

5.1.3

Output voltage clamp

This internal protection circuit clamps the output voltage to a maximum safe value, typically

4.5 V, if the input voltage exceeds this threshold.

5.1.4

Current limiting

When an overload event occurs, the current limiting circuit reduces the conductivity of the

power MOSFET, in order to clamp the output current at the value selected externally by

5.1.5

Thermal shutdown and Auto-retry function

If the device temperature exceeds the thermal latch threshold, typically 160 °C, the thermal

shutdown circuitry turns the power MOSFET off, thus disconnecting the load. The EN/Fault

pin of the device is automatically set to an intermediate voltage, in order to signal the

overtemperature event.

The STEF033 latch version can be reset from this condition either by cycling the supply

On the STEF033A auto-retry version, the power MOSFET will remain in an OFF state until

the die temperature drops below the hysteresis value. Once this happens, the internal auto-

retry circuit attempts to reset the device, pulling up the EN/Fault pin to the operative value.

5.2

As shown in Figure 1 the device uses an internal N-channel Sense FET with a fixed ratio, to

monitor the output current and limit it at the level set by the user.

The device has two levels of current limitation, depending on the load condition.

voltage decreases sharply, as in the case of a short-circuit on the output.

current level that is recognized by the device as an overload condition. Following this, the

current limit trip point is reached the device enters into current limitation, and the current to

by the load current slew-rate. The faster the current increase, the higher the current limit trip

point.