SAM-D21G_14 Datasheet, PDF (14/23 Pages) ATMEL Corporation – SMART ARM-Based Microcontroller

7. Packaging Information
7.1 Thermal Considerations
7.1.1 Thermal Resistance Data
Table 7-1 summarizes the thermal resistance data depending on the package.
Table 7-1. Thermal Resistance Data
Package Type
32-pin TQFP
48-pin TQFP
64-pin TQFP
32-pin QFN
48-pin QFN
64-pin QFN
θ_JA
68 °C/W
78.8 °C/W
66.7 °C/W
37.2 °C/W
33 °C/W
33.5 °C/W
θ_JC
25.8 °C/W
12.3 °C/W
11.9 °C/W
3.1 °C/W
11.4 °C/W
11.2 °C/W
7.1.2 Junction Temperature
The average chip-junction temperature, T_J, in °C can be obtained from the following:
where:
z θ_JA = package thermal resistance, Junction-to-ambient (°C/W), provided in Table 7-1.
z θ_JC = package thermal resistance, Junction-to-case thermal resistance (°C/W), provided in Table 7-1.
z θ_HEATSINK = cooling device thermal resistance (°C/W), provided in the device datasheet.
z P_D = device power consumption (W).
z T_A = ambient temperature (°C).
From the first equation, the user can derive the estimated lifetime of the chip and decide if a cooling device is necessary
or not. If a cooling device is to be fitted on the chip, the second equation should be used to compute the resulting average
chip-junction temperature T_J in °C.
Atmel | SMART SAM D21 [DATASHEET SUMMARY] 14
Atmel-42181DS–SAM-D21_Summary–09/2014