G1-300P-85-2.0
| Model | G1-300P-85-2.0 |
| Description | Processor Series Low Power Integrated x86 Solution |
| PDF file | Total 247 pages (File size: 4M) |
| Chip Manufacturer | NSC |
Geode™ GX1 Processor Series
Package Specifications
(Continued)
Table 7-2. Case-to-Ambient Thermal Resistance Examples @ 85°C
Core Voltage
(V
CC2
)
2.0V
(Nominal)
1.8V
(Nominal)
1.6V
(Nominal)
θ
CA
for Different Ambient Temperatures (°C/W)
Core
Frequency
300 MHz
266 MHz
233 MHz
200 MHz
Maximum
Power (W)
3.7
3.0
2.8
2.3
20°C
17
22
23
29
25°C
16
20
22
26
30°C
15
19
20
24
35°C
13
17
18
22
40°C
12
15
16
20
7.1.1 Heatsink Considerations
of a heatsink for particular operating environments. The
calculated values, defined as
θ
CA
, represent the required
ability of a particular heatsink to transfer heat generated by
the processor from its case into the air, thereby maintaining
the case temperature at or below 85°C. Because
θ
CA
is a
measure of thermal
resistivity,
it is inversely proportional to
the heatsink’s ability to dissipate heat or it’s thermal
conduc-
tivity.
Note:
A "perfect" heatsink would be able to maintain a
case temperature equal to that of the ambient air
inside the system chassis.
Looking at Table 7-2, it can be seen that as ambient tem-
perature (T
A
) increases,
θ
CA
decreases, and that as power
consumption of the processor (P) increases,
θ
CA
decreases. Thus, the ability of the heatsink to dissipate ther-
mal energy must increase as the processor power
increases and as the temperature inside the enclosure
increases.
While
θ
CA
is a useful parameter to calculate, heatsinks are
not typically specified in terms of a single
θ
CA
. This is
because the thermal resistivity of a heatsink is not constant
across power or temperature. In fact, heatsinks become
slightly less efficient as the amount of heat they are trying
to dissipate increases. For this reason, heatsinks are typi-
cally specified by graphs that plot heat dissipation (in watts)
vs. mounting surface (case) temperature rise above ambi-
ent (in °C). This method is necessary because ambient and
case temperatures fluctuate constantly during normal oper-
ation of the system. The system designer must be careful
to choose the proper heatsink by matching the required
θ
CA
with the thermal dissipation curve of the device under
the entire range of operating conditions in order to make
sure that the maximum case temperature (from table Table
heatsink, the system designer must make sure that the cal-
culated
θ
CA
falls above the curve (shaded area). The curve
itself defines the minimum temperature rise above ambient
that the heatsink can maintain.
See Figure 7-1 as an example of a particular heatsink
under consideration.
Mounting Surface Temperature
Rise Above Ambient – °C
50
40
30
20
10
0
θ
CA = 45/5 = 9
θ
CA = 45/9 = 5
2
4
6
8
10
Heat Dissipated - Watts
Figure 7-1. Heatsink Example
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