mpc8308 Freescale Semiconductor, Inc, mpc8308 Datasheet - Page 81

• Manufacturer Part Number: mpc8308
• Description: Mpc8308 Powerquicc Ii Pro Processor Hardware Specification
• Manufacturer: Freescale Semiconductor, Inc

the local ambient conditions explicitly as the board temperature provides a more precise description of the
local ambient conditions that determine the temperature of the device.
At a known board temperature, the junction temperature is estimated using the following equation:
where:
When the heat loss from the package case to the air can be ignored, acceptable predictions of junction
temperature can be made. The application board should be similar to the thermal test condition: the
component is soldered to a board with internal planes.
22.2.3
To determine the junction temperature of the device in the application after prototypes are available, the
thermal characterization parameter (
measurement of the temperature at the top center of the package case using the following equation:
where:
The thermal characterization parameter is measured per JESD51-2 specification using a 40 gauge type T
thermocouple epoxied to the top center of the package case. The thermocouple should be positioned so
that the thermocouple junction rests on the package. A small amount of epoxy is placed over the
thermocouple junction and over about 1 mm of wire extending from the junction. The thermocouple wire
is placed flat against the package case to avoid measurement errors caused by cooling effects of the
thermocouple wire.
23 System Design Information
This section provides electrical and thermal design recommendations for successful application of the
device
Freescale Semiconductor
T
T
R
P
T
T
Ψ
P
J
B
J
T
θ
D
D
JT
JB
= junction temperature (°C)
= junction temperature (°C)
= thermocouple temperature on top of package (°C)
= board temperature at the package perimeter (°C)
= power dissipation in the package (W)
= power dissipation in the package (W)
Experimental Determination of Junction Temperature
= thermal characterization parameter (°C/W)
= junction-to-board thermal resistance (°C/W) per JESD51–8
T
T
J
J
= T
= T
B
T
MPC8308 PowerQUICC II Pro Processor Hardware Specification, Rev. 1
+ (
+ (R
Ψ
θ
JT
JB
× P
× P
D
D
)
)
Ψ
JT
) can be used to determine the junction temperature with a
System Design Information
81