The max Junction temperature is the maximum temperature that the device tolerates to guarantee reliable operation. The system designer needs to ensure that TJ < TJmax to guarantee reliability. The TJmax for the device is 125 C.
The max power dissipation for the device can be calculated by Pd (max) = VDD (max) * IDD (max)
Pd = 3.6 * 12 = 43.2 mW
I will need to confirm the Theta Jb value and i will post it later here.