TSC695F ATMEL [ATMEL Corporation], TSC695F Datasheet - Page 37

• Manufacturer Part Number: TSC695F
• Description: Rad-Hard 32-bit SPARC Embedded Processor
• Manufacturer: ATMEL [ATMEL Corporation]

Package Description
Thermal Characteristics
4118H–AERO–06/03
The thermal performance of a package is measured by its ability to dissipate the power
required by the device into its surroundings. The electrical power drawn by the device
generates heat on the top surface of the die. This heat is conducted through the pack-
age to the surface and then transferred when there is surrounding air by convection.
Each heat transfer step has corresponding resistance, when there is surrounding air, to
the heat flow, which is given the value R θ , the thermal resistance coefficient. Subscripts
are added to the coefficient to specify the two points that the heat is transferred
between. Commonly used coefficients are R θ ja (junction to ambient air), R θ jc (junction
to case) and R θ ca (case to ambient).
An electrical analogy can be made, as shown in Figure 23, to illustrate the heat flow of a
package. The heat transfer can be characterized mathematically by the following
equation:
Figure 23. Thermal Model
Table 8. Thermal Characteristics
Tj Ta
–
–
–
R θ -
ja
jc
ja
jc
Where:
P = Device operating power (Watts)
Tj = Temperature of a junction on the device (°C)
Ta = Temperature of the surrounding ambient air (°C)
R θ ja = R θ jc + R θ ca in °C/W
=
P Rθja
×
Package
20 ~ 23
31 ~ 41
Value
0.4
0.4
Cavity
Unit
°C/W
Die
R θ ja
Temperature
25/90°C
Conditions
R θ jc
R θ ca
TSC695F
Stationary air
Heat Flow
Blown air
Air
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