MPC8248 Freescale Semiconductor, Inc, MPC8248 Datasheet - Page 11

• Manufacturer Part Number: MPC8248
• Description: Mpc8248 Powerquicc Ii Integrated Communications Processor
• Manufacturer: Freescale Semiconductor, Inc

4
Table 6
Discussions of each characteristic are provided in sections 4.1 through 4.7. For the these discussions,
P
4.1
An estimation of the chip junction temperature, T
where:
The junction-to-ambient thermal resistance is an industry standard value which provides a quick and easy
estimation of thermal performance. However, the answer is only an estimate; test cases have demonstrated
that errors of a factor of two (in the quantity T
Freescale Semiconductor
4
5
D
= (V
The leakage current is measured for nominal VDDH,VCCSYN, and VDD.
MPC8272 and MPC8271 only.
1
2
3
4
Junction-to-ambient—
single-layer board
Junction-to-ambient—
four-layer board
Junction-to-board
Junction-to-case
Junction-to-package top
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.
Thermal resistance between the die and the case top surface as measured by the cold plate method (MIL SPEC-883
Assumes no thermal vias
Thermal resistance between the die and the printed circuit board per JEDEC JESD51-8. Board temperature is
Thermal characterization parameter indicating the temperature difference between package top and the junction
Thermal Characteristics
T
R
P
describes thermal characteristics. Refer to
DD
A
D
θJA
Estimation with Junction-to-Ambient Thermal Resistance
= ambient temperature (ºC)
= power dissipation in package
× I
= package junction-to-ambient thermal resistance (ºC/W)
T
DD
J
= T
) + PI/O, where PI/O is the power dissipation of the I/O drivers.
3
Characteristic
2
1
A
MPC8272 PowerQUICC II™ Family Hardware Specifications, Rev. 1.5
+ (R
4
θJA
× P
D
)
Table 6. Thermal Characteristics
J
– T
J
Symbol
, in C can be obtained from the equation:
Table 2
A
R
R
R
R
R
) are possible.
θJA
θJA
θJB
θJC
θJT
for information on a given device’s package.
Value
27
21
19
16
11
8
2
°C/W
°C/W
°C/W
°C/W
°C/W
Unit
Natural convection
Natural convection
Thermal Characteristics
Air Flow
1 m/s
1 m/s
—
—
—
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