Legacy Fan Speed Control
110
Thermal and Mechanical Design Guidelines
The benefit of this upper limit will become more apparent when the fan speed
controller is responding to the on-die thermal sensor.
Figure
7-38. Thermistor Set Points
F
a
n S
p
ee
d
(RPM
)
Fan Inlet
Temperature (°C)
Full
Speed
30
38
Min.
Operating
Variable Speed Fan (VSF) Curve
F
a
n S
p
ee
d
(RPM
)
Fan Inlet
Temperature (°C)
Full
Speed
30
38
Min.
Operating
Variable Speed Fan (VSF) Curve
E.1.2
Minimum Fan Speed Set Point
The final aspect of thermal solution design is to determine the minimum speed the fan
will be allowed to operate. This value can be driven by the cooling requirements for
another portion of the design, such as the processor voltage regulator, or by
functional limits of the fan design.
Per the Fan Specification for 4 wire PWM Controlled Fans; there are three possible
options to consider
•
Type A: The fan will run at minimum RPM for all PWM duty cycle values less than
minimum duty cycle. This would be programmed into the fan controller located on
the fan hub. It can not be overridden by the external fan speed control.
•
Type B: The fan will run at minimum RPM for all non-zero PWM duty cycle values
less than minimum duty cycle and turn off the fan at 0% PWM duty cycle.
•
Type C: The fan will stop running when the current provided to the motor
windings is insufficient to support commutation. The fan would turn off at 0%
PWM duty cycle input.
For the reference thermal solution Type A was implemented.
Summary of Contents for Celeron Dual-Core E1000 Series
Page 10: ...10 Thermal and Mechanical Design Guidelines...
Page 26: ...Processor Thermal Mechanical Information 26 Thermal and Mechanical Design Guidelines...
Page 68: ...ATX Thermal Mechanical Design Information 68 Thermal and Mechanical Design Guidelines...
Page 86: ...Heatsink Clip Load Metrology 86 Thermal and Mechanical Design Guidelines...
Page 88: ...Thermal Interface Management 88 Thermal and Mechanical Design Guidelines...
Page 120: ...Legacy Fan Speed Control 120 Thermal and Mechanical Design Guidelines...
Page 126: ...Fan Performance for Reference Design 126 Thermal and Mechanical Design Guidelines...
Page 127: ...Fan Performance for Reference Design Thermal and Mechanical Design Guidelines 127...
