MPC8358 FREESCALE [Freescale Semiconductor, Inc], MPC8358 Datasheet - Page 86

• Manufacturer Part Number: MPC8358
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Thermal
23.2
For the following sections, P
See
23.2.1
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. As a general statement, 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
23.2.2
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
86
Table 5
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
2. Per JEDEC JESD51-2 and JEDEC JESD51-9 with the single layer board horizontal.
3. Per JEDEC JESD51-6 with the board horizontal. 1 m/sec is approximately equal to 200 linear feet per minute (LFM).
4. Thermal resistance between the die and the printed circuit board per JEDEC JESD51-8. Board temperature is
5. Thermal resistance between the die and the case top surface as measured by the cold plate method (MIL SPEC-883
6. Thermal characterization parameter indicating the temperature difference between package top and the junction
(board) temperature, ambient temperature, air flow, power dissipation of other components on the board, and board
thermal resistance.
measured on the top surface of the board near the package.
Method 1012.1).
temperature per JEDEC JESD51-2. When Greek letters are not available, the thermal characterization parameter
is written as Psi-JT.
MPC8358E PowerQUICC™ II Pro Processor Revision 2.1 PBGA Silicon Hardware Specifications, Rev. 1
Thermal Management Information
Estimation of Junction Temperature with Junction-to-Ambient
Thermal Resistance
Estimation of Junction Temperature with Junction-to-Board
Thermal Resistance
for typical power dissipations values.
Table 75. Package Thermal Characteristics for the PBGA Package (continued)
T
where:
T
T
R
P
A
J
J
θ
D
JA
= T
= junction temperature (°C)
= ambient temperature for the package (°C)
= power dissipation in the package (W)
Characteristic
D
= junction to ambient thermal resistance (°C/W)
A
= (V
+ (R
DD
θ
JA
X I
× P
DD
D
) + P
)
I/O
J
, can be obtained from the equation:
where P
I/O
is the power dissipation of the I/O drivers.
Symbol
ψ
JT
Value
J
- T
4
A
) are possible.
Freescale Semiconductor
°C/W
Unit
Notes
6