MPC5604P Microcontroller Data Sheet, Rev. 5
Preliminary—Subject to Change Without Notice
Freescale Semiconductor
30
3.3.1
General notes for specifications at maximum junction temperature
An estimation of the chip junction temperature, TJ, can be obtained from Equation 1: TJ = TA + (RθJA * PD)
Eqn. 1
where:
TA = ambient temperature for the package (oC)
RθJA= junction to ambient thermal resistance (oC/W)
PD = power dissipation in the package (W)
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
Equation 2 as the sum of a junction to case thermal resistance
and a case to ambient thermal resistance:
RθJA = RθJC + RθCA
Eqn. 2
Table 9. Thermal characteristics for 100-pin LQFP1
1 Thermal characteristics are targets based on simulation that are subject to change per device characterization.
No.
Symbol
Parameter
Conditions
Typical
Value
Unit
1RθJA
Thermal resistance junction-to-ambient
natural convection2
2 Junction-to-Ambient thermal resistance determined per JEDEC JESD51-3 and JESD51-6. Thermal test board
meets JEDEC specification for this package.
Single layer board—1s
56,3
°C/W
2RθJA
Thermal resistance junction-to-ambient
Four layer board—2s2p
43,4
°C/W
3RθJMA
Thermal resistance junction-to-ambien
t2@ 200 ft./min.3, single layer
board—1s
3 Flow rate of forced air flow.
43
°C/W
4RθJMA
Thermal resistance junction-to-ambien
t2@ 200 ft./min.
3, four layer
board—2s2p
35
°C/W
5RθJB
Thermal resistance junction to board4
4 Junction-to-Board thermal resistance determined per JEDEC JESD51-8. Thermal test board meets JEDEC
specification for the specified package.
—27
°C/W
6RθJCtop Thermal resistance junction to case (Top)
5
5 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.
—14
°C/W
7
Ψ
JT
Junction to package top natural convection6
6 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.
—3
°C/W