Intel® IXP42X Product Line of Network Processors and IXC1100 Control Plane Processor
4.3
Package Thermal Specifications
The thermal characterization parameter “ΨJT” is proportional to the temperature difference
between the top, center of the package and the junction temperature.
This can be a useful value for verifying device temperatures in an actual environment. By
measuring the package of the device, the junction temperature can be estimated, if the thermal
characterization parameter has been measured under similar conditions.
The use of ΨJT should not be confused with Θjc, which is the thermal resistance from the device
junction to the external surface of the package or case nearest the die attachment — as the case is
held at a constant temperature.
Case temperature = Junction Temperature - (ΨJT * Power Dissipation)
T
= T - (ΨJT * Power Dissipation)
JC
J
The case temperature can then be monitored to make sure that the maximum junction temperature
is not violated. Examples are given in the following sections.
Note:
For more information on ΨJT, refer to the EIA/JEDEC Standard 51-2, Section 4.
4.3.1
Commercial Temperature
“Commercial” temperature range is defined in terms of the ambient temperature range, which is
specified as 0° C to 70° C. The maximum power (P) is 2.4 W and the maximum junction
temperature (Tj) is 115 ° C.
ΨJT for commercial temperature is 0.89° C/W.
Using the preceding junction-temperature formula, the commercial temperature for a 266 MHz
device — assuming a maximum power of 2 W — would be:
T
T
= 115° C - (0.89 * 2.0)
= 113.22° C
JC
JC
4.3.2
Extended Temperature
“Extended” temperature range is defined in terms of the ambient temperature range, which is
specified as -40° C to 85° C. The maximum power (P) is 2.4 W and the maximum junction
temperature (Tj) is 115° C.
ΨJT for extended temperature is 0.32° C/W.
Using the preceding junction-temperature formula, the extended temperature for a 533 MHz device
— assuming a maximum power of 2.4 W — would be:
T
T
= 115° C - (0.32 * 2.4)
= 114.23° C
JC
JC
Datasheet
March 2005
81
Document Number: 252479, Revision: 005
INTEL [ INTEL ]
