GXM datasheet(195/244 Pages) NSC

195 / 244 page

Revision 3.1

195

www.national.com

8.0

Package Specifications

The thermal characteristics and mechanical dimensions

for the Geode GXm processor are provided on the follow-

ing pages.

8.1 THERMAL CHARACTERISTICS

Table 8-1 shows the junction-to-case thermal resistance

of the SPGA and BGA package and can be used to calcu-

late the junction (die) temperature under any given cir-

cumstance.

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°C to 85°C. As long as the case temperature of the

device is maintained within this range, the junction tem-

perature of the die will also be maintained within its allow-

able

operating

range.

However,

the

die

(junction)

temperature under a given operating condition can be cal-

culated by using the following equation:

TJ =TC +(P* θJC)

where:

TJ = Junction temperature (°C)

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

P = Power dissipation (W)

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

As stated previously, a maximum junction temperature is

not specified since a maximum case temperature is.

Therefore, the following equation can be used to calculate

the maximum thermal resistance required of the thermal

solution for a given maximum 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 8-2)

represents the maximum allowed thermal resistance of

the selected cooling solution which is required to maintain

the 85°C case temperature for the application in which the

device is used.

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.

Table 8-1. Junction-to-Case Thermal Resistance

for SPGA and BGA Packages

Package

θJC

SPGA

1.7

°C/W

BGA

1.1

°C/W

–

----------------------

–

----------------------

GXM Datasheet(PDF) 195 Page - National Semiconductor (TI)

GXM Datasheet(HTML) 195 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL