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Electrical Characteristics
MPC5510 Microcontroller Family Data Sheet, Rev. 3
Freescale Semiconductor
21
2.2
Thermal Characteristics
2.2.1
General Notes for Specifications at Maximum Junction Temperature
An estimation of the chip junction temperature, T
J
, can be obtained from the equation:
TJ = TA + (RθJA × PD)
Eqn. 1
where:
TA = ambient temperature for the package (
oC)
Eqn. 2
RθJA = junction to ambient thermal resistance (
oC/W)
Eqn. 3
PD = power dissipation in the package (W)
Eqn. 4
The supplied thermal resistances are provided based on JEDEC JESD51 series of standards to provide consistent values for
estimations and comparisons. The difference between the values determined on the single-layer (1s) board and on the four-layer
board with two signal layers and a power and a ground plane (2s2p) clearly demonstrate that the effective thermal resistance of
Table 4. Thermal Characteristics
Num
Characteristic
Symbol Unit
Value
208 MAPBGA
176 LQFP
144 LQFP
1
Junction to Ambient 1, 2
Natural Convection
(Single layer board)
1 Junction temperature is a function of on-chip power dissipation, package thermal resistance, mounting site (board)
temperature, ambient temperature, air flow, power dissipation of other components on the board, and board thermal
resistance.
2 Per SEMI G38-87 and JEDEC JESD51-2 with the single layer board horizontal.
RθJA
°C/W
44
38
43
2
Natural Convection
(Four layer board 2s2p)
3 Per JEDEC JESD51-6 with the board horizontal.
RθJA
°C/W
27
31
34
3
(@200 ft./min., Single layer board)
RθJMA °C/W
35
30
34
4
(@200 ft./min., Four layer board 2s2p)
RθJMA °C/W
24
25
28
5
Junction to Board 4
4 Thermal resistance between the die and the printed circuit board per JEDEC JESD51-8. Board temperature is measured on
the top surface of the board near the package.
RθJB
°C/W
16
20
22
6
Junction to Case 5
5 Indicates the average thermal resistance between the die and the case top surface as measured by the cold plate method
(MIL SPEC-883 Method 1012.1) with the cold plate temperature used for the case temperature.
RθJC
°C/W
8
6
7
Junction to Package Top 6
Natural Convection
6 Thermal characterization parameter indicating the temperature difference between package top and the junction
temperature per JEDEC JESD51-2.
Ψ
JT
°C/W
2