Specifications

Sensor Based Thermal Specification Design Guidance
30 Thermal/Mechanical Design Guide
5.3 Thermal Solution Design Process
Thermal solution design guidance for this specification is the same as with previous
products. The initial design must take into account the target market and overall
product requirements for the system. This can be broken down into several steps:
• Boundary condition definition
• Thermal design / modelling
•Thermal testing
5.3.1 Boundary Condition Definition
Using the knowledge of the system boundary conditions (e.g., inlet air temperature,
acoustic requirements, cost, design for manufacturing, package and socket mechanical
specifications and chassis environmental test limits) the designer can make informed
thermal solution design decisions.
The thermal boundary conditions for an ATX tower system are as follows:
•T
EXTERNAL
= 35 °C. This is typical of a maximum system operating environment
•T
RISE
= 4 °C. This is typical of a chassis compliant to CAG 1.1
•T
AMBIENT
= 39 °C (T
AMBIENT
= T
EXTERNAL
+ T
RISE
)
Based on the system boundary conditions, the designer can select a T
AMBIENT
and Ψ
CA
to use in thermal modelling. The assumption of a T
AMBIENT
has a significant impact on
the required Ψ
CA
needed to meet TTV T
CASEMAX
at TDP. A system that can deliver lower
assumed T
AMBIENT
can utilize a design with a higher Ψ
CA
, which can have a lower cost.
Figure 5-4 shows a number of satisfactory solutions for the processor.
Figure 5-3. Thermal solution Performance