MPC8358E_11 FREESCALE [Freescale Semiconductor, Inc], MPC8358E_11 Datasheet - Page 86

• Manufacturer Part Number: MPC8358E_11
• Description: PowerQUICC II Pro Processor Revision 2.1 PBGA Silicon
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Thermal
23.2.3
To determine the junction temperature of the device in the application after prototypes are available, the
Thermal Characterization Parameter (Ψ
measurement of the temperature at the top center of the package case using the following equation:
where:
The thermal characterization parameter is measured per JESD51-2 specification using a 40 gauge type T
thermocouple epoxied to the top center of the package case. The thermocouple should be positioned so
that the thermocouple junction rests on the package. A small amount of epoxy is placed over the
thermocouple junction and over about 1 mm of wire extending from the junction. The thermocouple wire
is placed flat against the package case to avoid measurement errors caused by cooling effects of the
thermocouple wire.
23.2.4
In some application environments, a heat sink will be required to provide the necessary thermal
management of the device. When a heat sink is used, the thermal resistance is expressed as the sum of a
junction to case thermal resistance and a case to ambient thermal resistance:
where:
R
change the case-to-ambient thermal resistance, R
sink, the airflow around the device, the interface material, the mounting arrangement on printed-circuit
board, or change the thermal dissipation on the printed-circuit board surrounding the device.
To illustrate the thermal performance of the devices with heat sinks, the thermal performance has been
simulated with a few commercially available heat sinks. The heat sink choice is determined by the
application environment (temperature, airflow, adjacent component power dissipation) and the physical
space available. Because there is not a standard application environment, a standard heat sink is not
required.
86
θ
JC
is device related and cannot be influenced by the user. The user controls the thermal environment to
T
T
Ψ
P
R
R
R
MPC8358E PowerQUICC II Pro Processor Revision 2.1 PBGA Silicon Hardware Specifications, Rev. 3
J
T
D
θ
θ
θ
JT
JA
JC
CA
= junction temperature (°C)
= thermocouple temperature on top of package (°C)
= power dissipation in the package (W)
Experimental Determination of Junction Temperature
Heat Sinks and Junction-to-Ambient Thermal Resistance
= junction-to-ambient thermal resistance (°C/W)
= junction-to-ambient thermal resistance (°C/W)
= junction-to-case thermal resistance (°C/W)
= case-to-ambient thermal resistance (°C/W)
T
R
J
θ
JA
= T
= R
T
+ (
θ
JC
Ψ
JT
+ R
× P
θ
CA
D
)
JT
) can be used to determine the junction temperature with a
θ
CA
. For instance, the user can change the size of the heat
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