mpc5604e Freescale Semiconductor, Inc, mpc5604e Datasheet - Page 24

• Manufacturer Part Number: mpc5604e
• Description: Mpc5604e Microcontroller Data Sheet
• Manufacturer: Freescale Semiconductor, Inc

Electrical characteristics
3.5.1
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. Unfortunately, there are two values in common usage: the value determined on a single layer board and the value
obtained on a board with two planes. For packages such as the PBGA, these values can be different by a factor of two. Which
value is closer to the application depends on the power dissipated by other components on the board. The value obtained on a
single layer board is appropriate for the 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.
When a heat sink is used, the thermal resistance is expressed in
and a case to ambient thermal resistance:
R
ambient thermal resistance, R
interface material, the mounting arrangement on printed circuit board, or change the thermal dissipation on the printed circuit
board surrounding the device.
To determine the junction temperature of the device in the application when heat sinks are not used, the Thermal
Characterization Parameter (
the top center of the package case using
24
JC
is device related and cannot be influenced by the user. The user controls the thermal environment to change the case to
3
4
5
6
where:
T
R
P
where:
R
R
R
where:
T

P
A
D
D
T
Flow rate of forced air flow.
Junction-to-Board thermal resistance determined per JEDEC JESD51-8. Thermal test board meets JEDEC
specification for the specified package.
Junction-to-Case at the top of the package determined using MIL-STD 883 Method 1012.1. The cold plate
temperature is used for the case temperature. Reported value includes the thermal resistance of the interface
layer.
Thermal characterization parameter indicating the temperature difference between the package top and the
junction temperature per JEDEC JESD51-2. When Greek letters are not available, the thermal
characterization parameter is written as Psi-JT.
JA
JA
JC
CA
JT
General notes for specifications at maximum junction temperature
= ambient temperature for the package (°C)
= junction to ambient thermal resistance (°C/W)
= power dissipation in the package (W)
= junction to ambient thermal resistance (°C/W)
= junction to case thermal resistance (°C/W)
= case to ambient thermal resistance (°C/W)
= thermocouple temperature on top of the package (°C)
= thermal characterization parameter (°C/W)
= power dissipation in the package (W)
CA
JT
) can be used to determine the junction temperature with a measurement of the temperature at
. For instance, the user can change the size of the heat sink, the air flow around the device, the
Preliminary—Subject to Change Without Notice
MPC5604E Microcontroller Data Sheet, Rev. 2
Equation
T
T
R
J
J
= T
JA
= T
J
3:
, can be obtained from
A
= R
T
+ (R
+ (
JC
JA
JT
+ R
Equation 2
x P
* P
CA
D
D
)
)
Equation
as the sum of a junction to case thermal resistance
1:
Freescale Semiconductor
Eqn. 1
Eqn. 3
Eqn. 2