STEF12

Typical application

Doc ID 019056 Rev 3

9/20

5.1.2

Normal operating condition

The STEF12 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 MOSFET

5.1.3

Output voltage clamp

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

15 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

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

5.2

R limit calculation

As shown in Figure 3, 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.

following theoretical formula, together with the graph in Figure 13: Current limit vs. RLimit.

Equation 1

5.3

output voltage ramp-up time.

Given the desired time interval

Δt during which the output voltage goes from zero to its

following theoretical formula:

Equation 2

95

--------------

=

C

dvdt

24

10

9

–

×Δt30x10

12

–

–

=