Junction Temperature

The junction temperature (T_J) of a semiconductor device is the temperature of the silicon die embedded in the device package. T_J depends on both the external environment (PCB design, ambient temperature, air flow speed, presence or absence of heatsink, etc.) and the internal power consumption. Silicon vendors always specify the T_J operating range on which the device data sheet parameters apply. As an example, for SAMA7G54 industrial grade devices, T_J ranges from -40°C to +105°C.

Even though SAMA7G5 devices can be operated up to their upper temperature limit, it is good practice to operate them at the lowest possible temperature for the following reasons:

1.As described in the ”SAMA7G5 Series Product Lifetime Estimation” application note, a lower junction temperature entails slower ageing mechanisms and hence a longer lifetime.
2.Such precaution reduces the overall power consumption of the device, which is appreciated in any power-constrained applications, and which avoids entering a vicious circle where more power means a higher junction temperature and therefore a higher leakage power.

SAMA7G5 devices feature an integrated temperature sensor to measure their junction temperature, with an accuracy of ±5°C. Microchip recommends to periodically measure T_J in any application. The frequency of these measurements is application-dependent, and should therefore be tuned to each specific case. For further details on the temperature sensor, refer to:

Application note “SAMA7G5 Series Temperature Sensor Calibration” (see Reference Documents)
Appendix A for Linux-specific information (temperature reading, etc.)