Specification Sheet

Thermal Management
98 Datasheet, Volume 1 of 2
Similarly for a system with a design target of 45 °C ambient, the Ψ
CA
at DTS = -1
needed will be 0.21 °C/W.
The second point defines the thermal solution performance (Ψ
CA
) at T
CONTROL
. The
following table lists the required Ψ
CA
for the various TDP processors.
These two points define the operational limits for the processor for DTS 1.1
implementation. At T
CONTROL
the fan speed must be programmed such that the
resulting Ψ
CA
is better than or equivalent to the required Ψ
CA
listed in the following
table. Similarly, the fan speed should be set at DTS = -1 such that the thermal solution
performance is better than or equivalent to the ΨCA requirements at T
AMBIENT-MAX
.
The fan speed controller must linearly ramp the fan speed from processor
DTS = T
CONTROL
to processor DTS = -1.
Figure 5-6. Digital Thermal Sensor (DTS) 1.1 Definition Points
Table 5-8. Digital Thermal Sensor (DTS) 1.1 Thermal Solution Performance Above
T
CONTROL
Processor
Ψ
CA
at DTS =
T
CONTROL
1, 2
At System
T
AMBIENT_MAX
= 30 °C
Ψ
CA
at DTS = -1
At System
T
AMBIENT_MAX
= 40 °C
Ψ
CA
at DTS = -1
At System
T
AMBIENT_MAX
= 45 °C
Ψ
CA
at DTS = -1
At System
T
AMBIENT_MAX
= 50 °C
Hexa Core GT2 95W 0.44 0.247 0.195 0.142
Hexa Core GT2 65W 0.763 0.477 0.4 0.323
Quad Core GT2 62W 0.775 0.49 0.41 0.329
Notes:
1. Ψ
CA
at "DTS = T
CONTROL
" is applicable to systems that have an internal T
RISE
(T
ROOM
temperature to
Processor cooling fan inlet) of less than 10 °C. In case the expected T
RISE
is greater than 10 °C, a
correction factor should be used as explained below. For each 1 °C T
RISE
above 10 °C, the correction
factor (CF) is defined as CF = 1.7 / (processor TDP)
2. Example: A chassis T
RISE
assumption is 12 °C for a 91 W TDP processor: CF = 1.7 / 91 W = 0.019 /W For
T
RISE
> 10 °C Ψ
CA
at T
CONTROL
= (Value provide in Column 2) – (T
RISE
– 10) * CF Ψ
CA
= 0.45 – (12 – 10)
0.019 = 0.41 °C/W In this case, the fan speed should be set slightly higher, equivalent to
Ψ
CA
= 0.41 °C/W