Thermally Advantaged Small Chassis (TASC) Design Guide

Section 2
E60781 7
2 Section 2
2.1 Thermally Advantaged Small Chassis Description
The critical thermal objective for processor cooling is to achieve a temperature rise
from external ambient to the inlet of the processor thermal solution fan to be less than
5 °C during a worst case system power load. This would equate to a 40°C fan inlet at
the maximum recommended room ambient temperature of 35°C. By meeting this
objective, fan heat sink solutions should have adequate boundary conditions to
properly cool the CPU and provide sufficient airflow to nearby components. Details on
thermocouple placement for CPU fan heat sink inlet temperature measurement can be
found in applicable Thermal Design Guide (TDG) documents.
It is a key feature in this design guide not to use special ducting or other features
beyond a vent location and pattern to meet thermal objectives. This allows platform
flexibility between legacy and future CPU locations without requiring chassis tooling
changes.
This design guide intends to provide guidance on the critical features that have
greatest impact on thermal performance. These are side vent size and location, free
area ratio, chassis height (or distance between fan inlet and chassis vent), and system
fan. The following will describe each of these features and the recommended
specifications to maintain an internal temperature condition below 40°C.
Figure 1. Generic Chassis Representation