2.4 Circuit Protection

The MCP1781 features current foldback protection during an output short-circuit event that occurs during normal operation. When the current foldback block detects an increase in load current, over the typical value of 450 mA, the output current and output voltage will start to decrease until the output current reaches a value of typically 10 mA (see Figure 4-16 and Figure 4-17).

If a short circuit is present during power-up, the part will enter current limit protection and a constant current of 450 mA will be maintained. The part will not enter current foldback.

The MCP1781 was tested using the AEC-Q100 test set-up in Figure 2-1. The testing conditions require the use of very high parasitic inductances on the input and output. For cases like this, it is required to prevent the output voltage going below ground with more than 1V. Note that the VOUT pin can withstand a maximum of –0.3 VDC (see Absolute Maximum Ratings). This can be achieved by placing a diode with the cathode to VOUT and the anode to ground.

Thermal shutdown functionality is present on the device and adds to the protection features of the part. Thermal shutdown is triggered at a typical value of 169°C and has a typical hysteresis of 11°C.