STPCI2 STMicroelectronics, STPCI2 Datasheet - Page 100

• Manufacturer Part Number: STPCI2
• Description: STPC ATLAS DATASHEET - X86 CORE PC COMPATIBLE SYS
• Manufacturer: STMicroelectronics

DESIGN GUIDELINES
6.4.5. THERMAL DISSIPATION
6.4.5.1. Power saving
Thermal dissipation of the STPC depends mainly
on supply voltage. When the system does not
need to work at the upper voltage limit, it may
therefore be beneficial to reduce the voltage to the
lower voltage limit, where possible. This could
save a few 100’s of mW.
The second area to look at is unused interfaces
and functions. Depending on the application,
some input signals can be grounded, and some
blocks not powered or shutdown. Clock speed
dynamic adjustment is also a solution that can be
used
management unit.
6.4.5.2. Thermal balls
The standard way to route thermal balls to ground
layer implements only one via pad for each ball
pad, connected using a 8-mil wire.
100/111
along
with
the
integrated
Figure 6-31. Ground Routing
Issue 1.0 - July 24, 2002
power
With such configuration the Plastic BGA package
does 90% of the thermal dissipation through the
ground balls, and especially the central thermal
balls which are directly connected to the die. The
remaining 10% is dissipated through the case.
Adding a heat sink reduces this value to 85%.
As a result, some basic rules must be followed
when routing the STPC in order to avoid thermal
problems.
As the whole ground layer acts as a heat sink, the
ground balls must be directly connected to it, as
illustrated in
enough, a second ground plane may be added.
When possible, it is important to avoid other
devices on-board using the PCB for heat
dissipation, like linear regulators, as this would
heat the STPC itself and reduce the temperature
range of the whole system, In case these devices
can not use a separate heat sink, they must not be
located just near the STPC
Figure
Pad for ground ball
6-31. If one ground layer is not
Thru hole to ground layer