MPC8347 FREESCALE [Freescale Semiconductor, Inc], MPC8347 Datasheet - Page 93

• Manufacturer Part Number: MPC8347
• Description: Integrated Host Processor Hardware Specifications
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

20.2
For the following sections, P
See
20.2.1
An estimation of the chip junction temperature, T
The junction to ambient thermal resistance is an industry-standard value that provides a quick and easy
estimation of thermal performance. Generally, the value obtained on a single layer board is appropriate for
a tightly packed printed circuit board. The value obtained on the board with the internal planes is usually
appropriate if the board has low power dissipation and the components are well separated. Test cases have
demonstrated that errors of a factor of two (in the quantity T
20.2.2
The thermal performance of a device cannot be adequately predicted from the junction to ambient thermal
resistance. The thermal performance of any component is strongly dependent on the power dissipation of
surrounding components. In addition, the ambient temperature varies widely within the application. For
Freescale Semiconductor
Junction-to-package natural convection on top
Notes
1. Junction temperature is a function of die size, on-chip power dissipation, package thermal resistance, mounting site (board)
2. Per SEMI G38-87 and JEDEC JESD51-2 with the single layer board horizontal.
3. Per JEDEC JESD51-6 with the board horizontal.
4. Thermal resistance between the die and the printed circuit board per JEDEC JESD51-8. Board temperature is measured on
5. Thermal resistance between the die and the case top surface as measured by the cold plate method (MIL SPEC-883 Method
6. Thermal characterization parameter indicating the temperature difference between package top and the junction temperature
temperature, ambient temperature, air flow, power dissipation of other components on the board, and board thermal
resistance.
the top surface of the board near the package.
1012.1).
per JEDEC JESD51-2. When Greek letters are not available, the thermal characterization parameter is written as Psi-JT.
Table 5
Thermal Management Information
Estimation of Junction Temperature with Junction-to-Ambient
Thermal Resistance
Estimation of Junction Temperature with Junction-to-Board
Thermal Resistance
MPC8347EA PowerQUICC II Pro Integrated Host Processor Hardware Specifications, Rev. 3
for I/O power dissipation values.
T
where:
J
Table 65. Package Thermal Characteristics for PBGA (continued)
= T
T
T
R
P
A
A
J
θ
D
Characteristic
+ (R
JA
= junction temperature (°C)
= ambient temperature for the package (°C)
= power dissipation in the package (W)
D
= junction to ambient thermal resistance (°C/W)
θ
= (V
JA
× P
DD
D
)
× I
DD
) + P
I/O
J
, can be obtained from the equation:
where P
I/O
J
- T
is the power dissipation of the I/O drivers.
A
) are possible.
Symbol
ψ
JT
Value
5
•C/W
Unit
Notes
Thermal
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