MPC866 Freescale Semiconductor, MPC866 Datasheet - Page 13

• Manufacturer Part Number: MPC866
• Description: (MPC859 / MPC866) Hardware Specifications
• Manufacturer: Freescale Semiconductor

If the board temperature is known, an estimate of the junction temperature in the environment can be made
using the following equation:
T
where:
If the board temperature is known and the heat loss from the package case to the air can be ignored,
acceptable predictions of junction temperature can be made. For this method to work, the board and board
mounting must be similar to the test board used to determine the junction-to-board thermal resistance,
namely a 2s2p (board with a power and a ground plane) and vias attaching the thermal balls to the ground
plane.
7.4
When the board temperature is not known, a thermal simulation of the application is needed. The simple
two-resistor model can be used with the thermal simulation of the application [2], or a more accurate and
complex model of the package can be used in the thermal simulation.
MOTOROLA
J
= T
B
R
T
P
+(R
D
B
θJB
= board temperature ºC
= power dissipation in package
Estimation Using Simulation
θJB x
= junction-to-board thermal resistance (ºC/W)
P
1 0 0
Figure 3. Effect of Board Temperature Rise on Thermal Behavior
D
9 0
8 0
7 0
6 0
5 0
4 0
3 0
2 0
1 0
)
0
0
Board Temperture Rise Above Ambient Divided by Package
Freescale Semiconductor, Inc.
For More Information On This Product,
MPC866/859 Hardware Specifications
2 0
Go to: www.freescale.com
Power
4 0
Thermal Calculation and Measurement
6 0
8 0
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