Datasheet

68
32072SH–AVR32–10/2012
AT32UC3A3
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 on page
68.
• θ
JC
= package thermal resistance, Junction-to-case thermal resistance (°C/W), provided in
Table 8-1 on page 68.
• 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 ”Regulator
characteristics” on page 43.
•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 TQFP144 40.3
°C/W
θ
JC
Junction-to-case thermal resistance TQFP144 9.5
θ
JA
Junction-to-ambient thermal resistance Still Air TFBGA144 28.5
°C/W
θ
JC
Junction-to-case thermal resistance TFBGA144 6.9
θ
JA
Junction-to-ambient thermal resistance Still Air VFBGA100 31.1
°C/W
θ
JC
Junction-to-case thermal resistance VFBGA100 6.9
T
J
T
A
P
D
θ
JA
×()+=
T
J
T
A
P(
D
θ(
HEATSINK
×θ
JC
))++=