GWIXP425BCT datasheet(81/134 Pages) INTEL

81 / 134 page

Intel® IXP42X Product Line of Network Processors and IXC1100 Control Plane Processor

Datasheet

March 2005

Document Number: 252479, Revision: 005

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.

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:

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:

Case temperature = Junction Temperature - (

ΨJT * Power Dissipation)

TJC = TJ - (ΨJT * Power Dissipation)

TJC = 115° C - (0.89 * 2.0)

TJC = 113.22° C

TJC = 115° C - (0.32 * 2.4)

TJC = 114.23° C

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