In our design, the T1042(with heat sink on the top of T1042) doesn't boot up at -20C when we turn on the cooling fans, if we turn off the fans, the T1042(with heat sink on the top of T1042) doesn't boot up at -35C, if we take off the heat sink and turn off the fans, the T1042 doesn't have boot up issue, it can boot up at -40C
We already checked the input system clock(DIFF_SYSCLK/DIFF_SYSCLK_B) at -40C, it looks like the same at room temperature. When T1042 doesn't boot up, PORESET_B and RESET_REQ_B both are HIGH, but HRESET_B is LOW, all the voltages level are look good. We tested the 1042 can boot up or cannot boot up by itself as temperature up and down without turn off the power. We even tested the hard-coded RCW setting, the T1042 doesn't boot up at cold temperature.
So I am just wondering if the T1042 has certain temperature protection when temperature reach to certain degree during power up?