SC1100 datasheet(343/348 Pages) NSC

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8.0

Package Specifications

8.1

THERMAL CHARACTERISTICS

The junction-to-case thermal resistance (

JC) of the TEPBGA package shown in Table 8-1 can be used to calculate the

junction (die) temperature under any given circumstance.

Note that there is no specification for maximum junction temperature given since the operation of the TEPBGA device is

guaranteed to a case temperature range of 0

°C to 85°C (see Table 7-2 on page 281). As long as the case temperature of

the device is maintained within this range, the junction temperature of the die will also be maintained within its allowable

operating range. However, the die (junction) temperature under a given operating condition 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)

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

These examples are given for reference only. The actual value used for maximum power (P) and ambient temperature (TA)

is determined by the system designer based on system configuration, extremes of the operating environment, and whether

active thermal management (via Suspend Modulation) of the GX1 processor is employed.

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)

= Maximum 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 equa-

tion can be simplified to:

where:

CA = θSA = Max heatsink-to-ambient thermal resistance (°C/W) allowed for thermal solution

The calculated

CA value (examples shown in Table 8-2 on page 344) represents the maximum allowed thermal resistance

of the selected cooling solution which is required to maintain the maximum TC (shown in Table 7-2 on page 281) for the

application in which the device is used.

Table 8-1.

JC (×C/W) for SC1100

Package

Max

(

°C/W)

TEPBGA without copper heat spreader

TEPBGA with copper heat spreader

θCS + θSA =

TC − TA

θCA =

TC − TA

SC1100 Datasheet(PDF) 343 Page - National Semiconductor (TI)

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