mpc5566 Freescale Semiconductor, Inc, mpc5566 Datasheet - Page 6

• Manufacturer Part Number: mpc5566
• Description: Mpc5566 High Performance Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Electrical Characteristics
3.2.1
An estimation of the device junction temperature, T
The thermal resistance values used are based on the JEDEC JESD51 series of standards to provide
consistent values for estimations and comparisons. The difference between the values determined for the
single-layer (1s) board compared to a four-layer board that has two signal layers, a power and a ground
plane (2s2p), demonstrate that the effective thermal resistance is not a constant. The thermal resistance
depends on the:
Connect all the ground and power balls to the respective planes with one via per ball. Using fewer vias to
connect the package to the planes reduces the thermal performance. Thinner planes also reduce the thermal
performance. When the clearance between the vias leave the planes virtually disconnected, the thermal
performance is also greatly reduced.
As a general rule, the value obtained on a single-layer board is within the normal range for the tightly
packed printed circuit board. The value obtained on a board with the internal planes is usually within the
normal range if the application board has:
The thermal performance of any component depends on the power dissipation of the surrounding
components. In addition, the ambient temperature varies widely within the application. For many natural
convection and especially closed box applications, the board temperature at the perimeter (edge) of the
package is approximately the same as the local air temperature near the device. Specifying the local
ambient conditions explicitly as the board temperature provides a more precise description of the local
ambient conditions that determine the temperature of the device.
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Construction of the application board (number of planes)
Effective size of the board which cools the component
Quality of the thermal and electrical connections to the planes
Power dissipated by adjacent components
One oz. (35 micron nominal thickness) internal planes
Components are well separated
Overall power dissipation on the board is less than 0.02 W/cm
where:
General Notes for Specifications at Maximum Junction Temperature
T
T
R
P
A
D
J
θJA
= T
= ambient temperature for the package (
= power dissipation in the package (W)
= junction to ambient thermal resistance (
A
+ (R
θJA
× P
MPC5566 Microcontroller Data Sheet, Rev. 2.0
D
)
J
, can be obtained from the equation:
o
C)
o
C/W)
2
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