Junction Temperature

The junction temperature (TJ) of a semiconductor device is the temperature of the silicon die embedded in the device package. TJ 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 TJ operating range on which the device data sheet parameters apply. As an example, for SAMA7G54 industrial grade devices, TJ 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. 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. 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 TJ 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: