AT32UC3L064_14 Datasheet, PDF (73/113 Pages) ATMEL Corporation – High-performance, Low-power 32-bit Atmel AVR Microcontroller

AT32UC3L016/32/64
8. Mechanical Characteristics
8.1 Thermal Considerations
8.1.1
Thermal Data
Table 8-1 summarizes the thermal resistance data depending on the package.
Table 8-1. Thermal Resistance Data
Symbol Parameter
Condition Package
Typ
θ_JA
Junction-to-ambient thermal resistance Still Air
TQFP48
63.2
θ_JC
Junction-to-case thermal resistance
TQFP48
21.8
θ_JA
Junction-to-ambient thermal resistance Still Air
QFN48
28.3
θ_JC
Junction-to-case thermal resistance
QFN48
2.5
θ_JA
Junction-to-ambient thermal resistance Still Air
TLLGA48
25.4
θ_JC
Junction-to-case thermal resistance
TLLGA48
12.7
Unit
°C/W
°C/W
°C/W
8.1.2
Junction Temperature
The average chip-junction temperature, T_J, in °C can be obtained from the following:
1. T_J = T_A + (P_D × θ_JA)
2. T_J = T_A + (P _D × (θ _HEATSINK + θ_JC ) )
where:
• θ_JA = package thermal resistance, Junction-to-ambient (°C/W), provided in Table 8-1.
• θ_JC = package thermal resistance, Junction-to-case thermal resistance (°C/W), provided in
Table 8-1.
• θ_{HEAT SINK} = cooling device thermal resistance (°C/W), provided in the device datasheet.
• P_D = device power consumption (W) estimated from data provided in the Section 7.4 on page
42.
• 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.
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32099IS–01/2012