Atmel AT32UC3L016, Manual

Page: 55 / 88

55
32099DS–06/2010
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.
8.1.2 Junction Temperature
The average chip-junction temperature, T
J
, in °C can be obtained from the following:
1.
2.
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 7.5 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.
Table 8-1. Thermal Resistance Data
Symbol Parameter Condition Package Typ Unit
θ
JA
Junction-to-ambient thermal resistance Still Air TQFP48 63.2
°
C/W
θ
JC
Junction-to-case thermal resistance TQFP48 21.8
θ
JA
Junction-to-ambient thermal resistance Still Air QFN48 28.3
°
C/W
θ
JC
Junction-to-case thermal resistance QFN48 2.5
θ
JA
Junction-to-ambient thermal resistance Still Air TLLGA48 30.06
°
C/W
θ
JC
Junction-to-case thermal resistance TLLGA48 TBD
T
J
T
A
P
D
θ
JA
× ( )
+ =
T
J
T
A
P
(
D
θ (
HEATSINK
× θ
JC
) )
+ + =