I post a forum about TPS65381;Supply rails;typical circuit.And I did not get any informations what I really needed.I described my question again and try my best to explain it much clearly.
I only use TPS65381 to supply 3.3V and 1.2V.And in the typical 12V input voltage, external N-MOS which connects to VDD1 pin feels much too hot. When the input power of 12V battery is 2.4W, I make the input voltage come down to the 5V.And now, the input power of battery is just 1.7W.In this way, the external N-MOS does not feel too hot. This is why I need to use low input voltage.
But in my project, I cannot supply above 5.8V to TPS65381 at initial power up.
And are there any methods that I can use to solve the problem of overheating? All of circuits and components which I used are all following the design of the datasheet.