Datasheet

600
Atmel | SMART SAM D20 [DATASHEET]
Atmel-42129K–SAM-D20_datasheet–06/2014
33. Packaging Information
33.1 Thermal Considerations
33.1.1 Thermal Resistance Data
Table 33-1 summarizes the thermal resistance data depending on the package.
Table 33-1. Thermal Resistance Data
33.1.2 Junction Temperature
The average chip-junction temperature, T
J
, in °C can be obtained from the following equations:
Equation 1
Equation 2
where:
z θ
JA
= package thermal resistance, Junction-to-ambient (°C/W), provided in Table 33-1
z θ
JC
= package thermal resistance, Junction-to-case thermal resistance (°C/W), provided in Table 33-1
z θ
HEATSINK
= cooling device thermal resistance (°C/W), provided in the manufacturer datasheet
z P
D
= device power consumption (W)
z T
A
= ambient temperature (°C)
From “Equation 1” , 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, “Equation 2” should be used to compute the resulting average chip-
junction temperature T
J
in °C.
Package Type θ
JA
θ
JC
32-pin TQFP 68°C/W 25.8°C/W
48-pin TQFP 78.8°C/W 12.3°C/W
64-pin TQFP 66.7°C/W 11.9°C/W
32-pin QFN 37.2°C/W 3.1°C/W
48-pin QFN 33°C/W 11.4°C/W
64-pin QFN 33.5°C/W 11.2°C/W
T
J
T
A
P
D
θ
JA
×()+=
T
J
T
A
P
D
θ
HEATSINK
θ
JC
+()×()+=