GX1 datasheet(207/247 Pages) NSC

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7.0

Package Specifications

The thermal characteristics and mechanical dimensions for

the Geode GX1 processor are provided on the following

pages.

7.1

THERMAL CHARACTERISTICS

Table 7-1 shows the junction-to-case thermal resistance of

the SPGA and BGA package and can be used to calculate

the junction (die) temperature under any given circum-

stance.

Note that there is no specification for maximum junction

temperature given since the operation of both SPGA and

BGA devices are guaranteed to a case temperature range

of 0°Cto 85°C (see Table 6-4 on page 190). As long as the

case temperature of the device is maintained within this

range, the junction temperature of the die will also be main-

tained within its allowable operating range. However, the

die (junction) temperature under a given operating condi-

tion can be calculated by using the following equation:

TJ =TC +(P* θJC)

where:

TJ = Junction temperature (°C)

TC = Case temperature at top center of package (°C)

P = Maximum power dissipation (W)

C = Junction-to-case thermal resistance (°C/W)

These examples are given for reference only. The actual

value used for maximum power (P) and ambient tempera-

ture (TA) is determined by the system designer based on

system configuration, extremes of the operating environ-

ment, and whether active thermal management (via Sus-

pend Modulation) of the processor is employed.

A maximum junction temperature is not specified since a

maximum case temperature is. Therefore, the following

equation canbeusedtocalculate themaximum thermal

resistance required of the thermal solution for a given max-

imum ambient temperature:

where:

CS = Max case-to-heatsink thermal resistance

(°C/W) allowed for thermal solution

SA = Max heatsink-to-ambient thermal resistance

(°C/W) allowed for thermal solution

TA = Max ambient temperature (°C)

TC = Max case temperature at top center of package

(°C)

P = Max power dissipation (W)

If thermal grease is used between the case and heatsink,

CS will reduce to about 0.01 °C/W. Therefore, the above

equation can be simplified to:

where:

CA = θCS = Max case-to-ambient thermal resistance

(°C/W) allowed for thermal solution.

The calculated

CA value (examples shown in Table 7-2 on

page 208) represents the maximum allowed thermal resis-

tance of the selected cooling solution which is required to

maintain the maximum TC (shown in Table 6-4 on page

190) for the application in which the device is used.

Table 7-1. Junction-to-Case Thermal Resistance

for SPGA and BGA Packages

Package

SPGA

1.7

°C/W

BGA

1.1

°C/W

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