SAM-R21E_14 datasheet(17/22 Pages) ATMEL

17 / 22 page

Atmel | SMART SAM R21 [PRELIMINARY DATASHEET SUMMARY]

Atmel-42223AS–SAM-R21_Summary–07/2014

Packaging Information

8.1

Thermal Considerations

8.1.1

Thermal Resistance Data

Table 8-1 summarizes the thermal resistance data depending on the package.

Table 8-1.

Thermal Resistance Data

8.1.2

Junction Temperature

The average chip-junction temperature, TJ, in °C can be obtained from the following:

where:

θJA = package thermal resistance, Junction-to-ambient (°C/W), provided in Table 8-1.

θJC = package thermal resistance, Junction-to-case thermal resistance (°C/W), provided in Table 8-1.

θHEATSINK = cooling device thermal resistance (°C/W), provided in the device datasheet.

PD = device power consumption (W).

TA = 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 TJ in °C.

Package Type

θJA

θJC

32-pin QFN

37.2

°C/W

3.1

°C/W

48-pin QFN

°C/W

11.4

°C/W

SAM-R21E Datasheet(PDF) 17 Page - ATMEL Corporation