mpc5604p Freescale Semiconductor, Inc, mpc5604p Datasheet - Page 30

• Manufacturer Part Number: mpc5604p
• Description: Mpc5604p Microcontroller Data Sheet
• Manufacturer: Freescale Semiconductor, Inc

3.3.1
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 (Ψ
the top center of the package case using
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.
References:
Semiconductor Equipment and Materials International
3081 Zanker Road
San Jose, CA 95134 U.S.A.
[phone]
30
θJC
is device related and cannot be influenced by the user. The user controls the thermal environment to change the case to
where:
T
R
P
where:
R
R
R
where:
T
Ψ
P
A
D
D
T
θJA
θJA
θJC
θCA
JT
= thermocouple temperature on top of the package (°C)
= power dissipation in the package (W)
= power dissipation in the package (W)
= ambient temperature for the package (
= thermal characterization parameter (°C/W)
= junction to case thermal resistance (°C/W)
General Notes for Specifications at Maximum Junction Temperature
= junction to ambient thermal resistance (
= junction to ambient thermal resistance (°C/W)
= case to ambient thermal resistance (°C/W)
θCA
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
MPC5604P Microcontroller Data Sheet, Rev. 3
Equation
R
T
T
θJA
J
J
J
3:
, can be obtained from
= T
= T
o
C)
= R
A
T
o
+ (R
+ (Ψ
C/W)
θJC
θJA
JT
+ R
Equation 2
x P
* P
θCA
D
D
)
)
Equation
as the sum of a junction to case thermal resistance
1:
Freescale Semiconductor
Eqn. 1
Eqn. 2
Eqn. 3