Thermal
Table 83. Package Thermal Characteristics (continued)
Rating
Junction to case
Board
—
Symbol
R
ΘJC
Value
0.5
Unit
Notes
5
°
C/W
Notes:
1. Junction temperature is a function of die size, on-chip power dissipation, package thermal resistance, mounting site (board)
temperature, ambient temperature, air flow, power dissipation of other components on the board, and board thermal
resistance
2. Per JEDEC JESD51-2 with the single-layer board (JESD51-3) horizontal.
3. Per JEDEC JESD51-6 with the board (JESD51-7) horizontal.
4. Thermal resistance between the die and the printed circuit board per JEDEC JESD51-8. Board temperature is measured
on the top surface of the board near the package.
5. Thermal resistance between the active surface of the die and the case top surface determined by the cold plate method
(MIL SPEC-883, Method 1012.1).
20.1
Temperature Diode
The MPC8572E has a temperature diode on the microprocessor that can be used in conjunction with other
system temperature monitoring devices (such as Analog Devices, ADT7461™). These devices use the
negative temperature coefficient of a diode operated at a constant current to determine the temperature of
the microprocessor and its environment. It is recommended that each MPC8572E device be calibrated.
The following are the specifications of the on-board temperature diode:
V
f
> 0.40 V
V
f
< 0.90 V
Operating range 2–300
μA
Diode leakage < 10 nA @ 125°C
An approximate value of the ideality may be obtained by calibrating the device near the expected
operating temperature.
Ideality factor is defined as the deviation from the ideal diode equation:
qV
f
___
I
fw
= I
s
e
nKT
– 1
Another useful equation is:
H
V
H
– V
L
= n
__
ln
__
KT
q
I
I
L
Where:
I
fw
= Forward current
I
s
= Saturation current
V
d
= Voltage at diode
MPC8572E PowerQUICC III Integrated Processor Hardware Specifications, Rev. 4
Freescale Semiconductor
123
FREESCALE [ FREESCALE SEMICONDUCTOR, INC ]
