I have some questions about "LM1117".
1. What does "junction temperature" mean in section 6.5 of the datasheet?
2. In particular, the maximum junction temperature seems to be the maximum allowed temperature, so what does the minimum junction temperature value mean?
3. Can I operate the LM1117 (not the LM1117i) at an ambient temperature of -32 degrees Celsius?
Hi Wanjin,
The junction temperature is internal temperature of the linear regulator. Due to the fact that linear regulators are power dissipative devices, the junction temperature will be higher than the ambient temperature.
The operating junction temperature range is the temperatures for which the LM1117 is designed, characterized, and tested to operate within. For reliable operation and to meet the performance depicted within the datasheet, the internal temperature (junction temperature) of the regulator must be within the operating junction temperature range.
No, the LM1117 has a minimum operating junction temperature range of 0 C. Only the LM1117I is designed, characterized, and tested to operate with a junction temperature below 0 C.
You can learn more about thermals with regards to linear regulators in chapter 3 of the LDO Basics e-book:
Very Respectfully,
Ryan
