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Passive system environment describes a chassis with either a power supply fan or a built-in system fan. This information should be used in conjunction with the Thermal and Mechanical Design Guide (TMDG) published for the Intel Atom processor D2000 series. The TMDG contains detailed package information and thermal mechanical specifications for the processors. The TMDG also contains information on how to enable a completely fanless design provided the right usage scenario and boundary conditions are observed for optimal thermal design. While the TMSDG has a section on thermal design for passive system environments (page 32), the information in this section can also be used to complement the TMDG. 2.6.1.1 Definition of Terms Term Description TA The measured ambient temperature locally surrounding the processor. The ambient temperature should be measured just upstream of a passive heatsink. TJ Processor junction temperature. .JA Junction-to-ambient thermal characterization parameter (psi). A measure of thermal solution performance using total package power. Defined as (TJ - TA)/TDP. Note: Heat source must be specified for . measurements. TIM Thermal Interface Material: the thermally conductive compound between the heatsink and the processor die surface. This material fills the air gaps and voids, and enhances the transfer of the heat from the processor die surface to the heatsink. TDP Thermal Design Power: a power dissipation target based on worst-case applications. Thermal solutions should be designed to dissipate the thermal design power. TA external The measured external ambient temperature surrounding the chassis. The external ambient temperature should be measured just upstream of the chassis inlet vent. 2.6.1.2 Thermal Specifications Guideline Terms Requirements TA . 50 °C TJ . 100 °C .JA . 3.85 °C/W TIM Honeywell PCM45F TDP 10 W TA external . 35 °C 2.6.1.3 Heatsink Design Guideline Maximum heatsink size (Note) 87 x 52 x 29 mm Heatsink mass . 63.6 grams Retention type Spring loaded fasteners Heatsink preload 13.2 lb Note: Refers to the heatsink installed on the board. 2.6.1.4 Chassis Design Guideline The pin fin heatsink design used on this board will be able to dissipate up to 10 W of processor power in most of the passively enabled system chassis. This board is targeted for 3-7 liters volumetric or larger, desktop/tower orientation, mini-ITX and microATX chassis with a system fan. The recommended fan type is an exhaust fan. For best thermal performance, it is recommended that the system fan provide reasonable airflow directly over all the major components on the board. The pin fin heatsink is designed to have the best thermal performance when airflow direction is parallel to the heatsink fins. The processor on the board will generate the highest amount of heat, leading to high ambient temperature within the chassis. The system fan should be located near the board region in order to effectively regulate airflow (see Figure 18). A system fan located further away from the board region, i.e., at the optical disk drive or hard disk drive region, will be less effective in controlling the local ambient temperature. Regardless of where the system fan is located, the maximum local ambient temperature as defined by TA should be capped at 50 °C. Chassis inlet vents should also provide adequate openings for airflow to pass through. The recommended free- area-ratio of chassis vents should be equal to or greater than 0.53. By using the reference pin fin heatsink, most chassis with a system fan enabled should have local ambient temperature safely below the 50 °C limit. Figure 18. Fan Location Guide for Chassis Selection (Chassis Orientation is Not Restricted) For all chassis configurations, the heatsink performance parameter, .JA should be less than 3.85 °C/W. The detail thermal measurement metrology is described in the TMSDG. For chassis that fail to meet the thermal specifications guideline highlighted above, an actively cooled heatsink solution should be used. 2.7 Power Consumption Power measurements were performed to determine bare minimum and likely maximum power requirements from the board, as well as attached devices, in order to facilitate power supply rating estimates for specific system configurations. 2.7.1 Minimum Load Configuration Minimum load refers to the power demand placed on the power supply when using a bare system configuration with minimal power requirement conditions. Minimum load configuration test results are shown in Table 32. The test configuration was defined as follows: • 2 GB DDR3/1066 MHz SO-DIMM • USB keyboard and mouse • LAN linked at 1000 Mb/s • DOS booted via network (PXE); system at idle • All on board peripherals enabled (serial, parallel, audio, …) Table 32. Minimum Load Configuration Current and Power Results Output Voltage 3.3 V 5 V 12 V -12 V 5 VSB Minimum Load 0.89 A 1.06 A 0.14 A 0.08 A 0.10 A 2.7.2 Maximum Load Configuration Maximum load refers to the incremental power deman...