G-4
MPC561/MPC563 Reference Manual
MOTOROLA
Thermal Characteristics
G.4
Thermal Characteristics
An estimation of the chip junction temperature, TJ, in °C can be obtained from the equation:
TJ = TA + (RθJA x PD)
where:
TA = ambient temperature (°C)
RθJA = package junction to ambient resistance (°C/W)
PD = power dissipation in package
The junction to ambient thermal resistance is an industry standard value which provides a
quick and easy estimation of thermal performance. Unfortunately, the answer is only an
estimate; test cases have demonstrated that errors of a factor of two are possible. As a result,
more detailed thermal characterization is supplied.
Table G-2. Thermal Characteristics
Characteristic
Symbol
Value
Unit
BGA Package Thermal Resistance,
Junction to Ambient – Natural Convection
RθJA
47.3 1, 2, 3
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
the board thermal resistance.
2 Per SEMI G38-87 and JESD51-2 with the board horizontal.
3 These values are the mean + 3 standard deviations of characterized data.
°C/W
BGA Package Thermal Resistance,
Junction to Ambient – Four layer (2s2p) board, natural
convection
RθJMA
4 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
the board thermal resistance.
5 Per JESD51-6 with the board horizontal.
°C/W
BGA Package Thermal Resistance,
Junction to Board
RθJB
6 Thermal resistance between the die and the printed circuit board (Four layer (2s2p) board, natural convection).
°C/W
BGA Package Thermal Resistance,
Junction to Case (top)
RθJT
7 Indicates the 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.
°C/W
BGA Package Thermal Resistance,
Junction to Package Top, Natural Convection
ΨJT
1.6 8
8 Thermal characterization parameter indicating the temperature difference between package top and the
junction temperature per EIA/JESD51-2.
°C/W