AMD SC1201 Thermal Characteristics, Θjc ×C/W, Case-to-Ambient Thermal Resistance Example @ 85C

Package Specifications 32579B

Package Specifications10

10.1Thermal Characteristics

The junction-to-case thermal resistance (θJC) of the pack- ages shown in Table 10-1can be used to calculate the junction (die) temperature under any given circumstance.

Table 10-1. θJC (×C/W)

Package	Max (°C/W)
BGU481	5

Note that there is no specification for maximum junction temperature given since the operation of the device is guaranteed to a case temperature range of 0°C to 85°C (see Table 9-3 on page 366). As long as the case tempera- ture of the device is maintained within this range, the junc- tion temperature of the die will also be maintained within its allowable operating range. However, the die (junction) tem- perature under a given operating condition can be calcu- lated 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)

θJC = 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 GX1 module 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 max- imum ambient temperature:

θCS + θSA = TC − TA

P

where:

θCS = Max case-to-heatsink thermal resistance (°C/W) allowed for thermal solution

θSA = 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 = Maximum power dissipation (W)

If thermal grease is used between the case and heatsink, θCS will reduce to about 0.01 °C/W. Therefore, the above equation can be simplified to:

θCA = TC − TA

P

where:

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

The calculated θCA value (examples shown in Table 10-2)represents the maximum allowed thermal resistance of the selected cooling solution which is required to maintain the

maximum TCASE (shown in Table 9-3 on page 366) for the application in which the device is used.

Table 10-2. Case-to-Ambient Thermal Resistance Example @ 85°C

Core Voltage				θCA for Different Ambient Temperatures (°C/W)
(VCORE)	Core	Maximum
			20°C		25°C	30°C	35°C	40°C
(Nominal)	Frequency	Power (W)
1.8V	266 MHz	3.32	19.58		18.07	16.57	15.06	13.55

AMD Geode™ SC1200/SC1201 Processor Data Book 437