Why does the PMOS burn out in a buck boost converter when I increase the power supply voltage?
Based on the schematic, you are driving the gate with 3.3V and GND. Since it is a PMOS, it must be driven with VIN to turn it off, and GND to turn it on. At least Vgs should be larger than 3.3V to turn it on properly, perhaps even 6V based on the gate charge curves.