Sun Microsystems SME5224AUPA-400 manual Temperature Estimating and Measuring Methods, Air Velocity

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UltraSPARC™-II CPU Module

SME5224AUPA-400400 MHz CPU, 4.0 MB E-Cache

Temperature Estimating and Measuring Methods

The following methods can be used to estimate air cooling requirements and calculate junction temperature based on thermo-couple temperature measurements.

Airflow Cooling Measurement Method

The relationship between air temperature and junction temperature is described in the following thermal equation:

Tj = Ta + [Pd (θjc + θcs + θsa)]

Note: Testing is done with the worst-case power draw, software loading, and ambient air temperature.

Determination of the ambient air temperature (Ta) and the “free-stream” air velocity is required in order to apply the airflow method. The table "Heatsink-to-Air Thermal Resistance," illustrates the thermal resistance between the heatsink and air (θsa).

Note that the airflow velocity can be measured using a velocity meter. Alternatively it may be determined by knowing the performance of the fan that is supplying the airflow. Calculating the airflow velocity is difficult. It is subject to the interpretation of the term “free-stream.”

Note: The Airflow Cooling Estimate method is an estimate. Use it solely when an approximate value suffices. Accuracy can only be assured using the Case Temperature measuring method or the Heatsink Temperature measuring method. Apply these methods to insure a reliable performance.

"Heatsink-to-Air Thermal Resistance," specifies the thermal resistance of the heatsink as a function of the air velocity.

Heatsink-to-Air Thermal Resistance

Air Velocity

 

 

 

 

 

 

 

 

(ft/min) [1]

150

200

300

400

500

650

800

1000

θSA (°C/W) [2]

1.21

1.05

0.91

0.84

0.78

0.72

0.67

0.64

 

 

 

 

 

 

 

 

 

1.Ducted airflow through the heatsinks.

2.Airflow direction parallel to the shorter axis of the pin-fin heatsink (1.9"L x 3.6"W x 1.1"H)

Air Velocity Specifications

These specifications are recommended for a typical configuration:

Airflow Topside

150 LFM @ 30 °C up to 2,000 feet, altitude, maximum

300 LFM @ 40 °C up to 10,000 feet, altitude, maximum Airflow Bottomside

100 LFM @ 30 °C up to 2,000 feet, altitude, maximum

150 LFM @ 40 °C up to 10,000 feet, altitude, maximum

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Sun Microsystems, Inc

July 1999

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Contents Module Features Module Benefits Module DescriptionEase of System Design PerformanceUltraSPARC-II CPU CPU Features CPU BenefitsCPU Description UltraSPARC-II Data Buffer UDB-II Data Buffer DescriptionExternal Cache Description Block Diagram Module Component OverviewUPA Interconnect UPA Connector PinsSystem Interface Jtag Interface Module PowerModule ID Signal Description Signal Type Name and FunctionSystem Interface Clock InterfaceInitialization Interface Miscellaneous SignalsJTAG/Debug Interface Module Clocks System ClocksSystem Clock Distribution Tested CPU to UPAClock Signal Distribution Electrical Characteristics Symbol Parameter Rating UnitsSymbol Parameter Min Typ Max Units Absolute Maximum RatingsSymbol Parameter Conditions Min Typ Max Units DC CharacteristicsModule Power Consumption UPA Data Bus Spice Model Module System Loading Example for UPADATA, UpaeccSetup and Hold Time Specifications Upaclk Module ClocksCpuclk Module Clock Clock BuffersMin Max Unit Propagation Delay, Output Hold Time SpecificationsTiming Measurement Waveforms Mechanical Specifications CPU Module ComponentsCPU Module Side View Thermal Specifications Two Step Approach to Thermal DesignThermal Definitions and Specifications Term Definition Specification CommentsTemperature Estimating and Measuring Methods Airflow Cooling Measurement MethodAir Velocity Specifications Air VelocityCase Temperature Measuring Method Heatsink Temperature Measuring MethodJtag Testability AC Characteristics Jtag TimingMHz CPU MHz TCK Symbol Parameter Signals Conditions Jtag Ieee 1149.1 Timing UPA Connector PIN Assignments TOP View PinUPA Connector PIN Assignments Bottom View Vddcore GND Vddcore GND Vddcore UPAPORTID1Value Parameter Conditions Min Typ Storage and Shipping SpecificationHandling CPU Modules Ordering Information Document Revision HistoryPart Number CPU Speeds Description Date Document No ChangeSun Microsystems, Inc UltraSPARC -II CPU Module UltraSPARC-II CPU Data Buffer Description Block Diagram System Interface Module ID System Interface JTAG/Debug Interface UPA and CPU Clocks Clock Signal Distribution Absolute Maximum Ratings DC Characteristics UPA Data Bus Spice Model Upaclk Module Clocks Propagation Delay, Output Hold Time Specifications Mechanical Specifications CPU Module Side View Two Step Approach to Thermal Design Thermal Definitions and Specifications Temperature Estimating and Measuring Methods Case Temperature Measuring Method AC Characteristics Jtag Timing Jtag Ieee 1149.1 Timing UPA Connector PIN Assignments TOP View UPA Connector PIN Assignments Bottom View Storage and Shipping Specification Ordering Information Sun Microsystems, Inc
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