PROFET (PROtected Field Effect Transistors) is our High-Side smart power switch brand. It consists of a MOSFET, a gate driver with charge pump, and multiple protection and diagnosis features.

In addition, several protection features are integrated. For example, short circuit protection can protect the MOSFET if a short to ground/battery occurs.

The overvoltage protection ensures the MOSFET will not be damaged during load dump transients or other high voltage events (assuming the transient pulse energy is within specified limits). The reverse battery protection keeps the smart switch safe if the battery polarity is reversed (current may flow, but the device will not be

damaged). The current limit feature limits the maximum current that the MOSFET switch can source. This again helps to protect the switch from short to ground/battery conditions. The overtemperature protection is

enabled if the temperature of the MOSFET junction reaches unsafe levels: the switch is turned off stopping the current flow completely.

Finally, diagnostics are included so the smart switch can provide feedback to a microcontroller if a fault condition is detected.

Overtemperature and overcurrent protection

Typically, the overtemperature protection is enabled if the temperature of the junction reaches unsafe levels, e.g. where the load current might not be high enough to be detected by the diagnostics. However, maintained for some time, the load current will actually heat the device and trigger the overtemperature protection. For that, all PROFET have an integrated temperature sensor.

To understand the over temperature and overcurrent protection, let’s take a look at this graph.

Once the PROFET is on (IN=1) and the diagnosis is enable (DEN=1), it will track the accuracy of the current sense (I IS ). As you can see on the graph, in the case where the load current I L is below the current limit, no fault will be detected. When maintained for a long time, I L brings the junction temperature T J to its absolute limit. The fault is detected and the over temperature protection kicks in.

In for some PROFET (like PROFET+2 (link)), there is also a dynamic overtemperature protection, that watches the dynamic variation of the junction temperature to detect a fault.

Unlike the overtemperature protection, the overcurrent protection is triggered instantaneously, as soon as the load current reaches the tripping current.

Once the protection has been triggered

Depending on the device, the protection, whether it is temperature, voltage or current, can be done:

- by limitation (the maximum current which the MOSFET high side switch can source is limited)

- by tripping (the channel is shut down).

There are two ways of register a fault conditions:

After the intervention of the protection, there are two ways to reactive the device:

- by latch (the device stays off and can only be reactivated by the microcontroller)

- by restart (once the temperature is below a certain threshold, without the need of the microcontroller).

More recent product families like PROFET+2 EPA (link) integrated an intelligent Auto-Restart function, where the channel is allowed to switch on a few times before switching off definitely, in case the conditions for switching on were not met.

Other protections

For most of the PROFET Smart Switches, other protections are also included:

Loss of ground protection

Reverse of polarity protection

Undervoltage protection.

For more information, please refer to the datasheets.