Intel 640 User Guide - Page 55

Acoustic Fan Speed Control

R

Thermal/Mechanical Design Guide

55

6.3

Board and System Implementation

Once the thermal solution is defined, the system designer and board designer can define the fan

speed control implementation. The first step is to select the appropriate fan speed controller

(FSC). Figure 17 shows the major connections for a typical implementation.

Figure 17. Example Acoustic Fan Speed Control Implementation

Pulse Width

Modulation (PWM)

Tachometer

Thermal Diode

(2 wires)

+12V

GND

Sys

Ambient

(Opt)

Sys Fan

4wire

PWM

(2x)

T

CONTROL

Inlet Ambient

(Thermistor)

4-Pin Fan

Header

HS Fan

Processor

Fan Speed

Controller

Pulse Width

Modulation (PWM)

Tachometer

Thermal Diode

(2 wires)

+12V

GND

Sys

Ambient

(Opt)

Sys Fan

4wire

PWM

(2x)

T

CONTROL

BIOS

Inlet Ambient

(Thermistor)

4-Pin Fan

Header

A number of major manufacturers have FSC components that include the necessary functionality

to measure the temperature of the on-die thermal diode and output a PWM signal. These

components can be a discrete device or a super I/O (SIO) with the functionality embedded. The

following vendors currently have components that could be suitable: Analog Devices, ITE,

Maxim, National Semiconductor, SMSC and Winbond. Consult their web sites or local sales

representatives for a part suitable for your design. See Appendix E

for further details on the

motherboard requirements

6.3.1

Choosing Fan Speed Control Settings

Fan speed control algorithms allow the system thermal engineer a number of options to consider.

The typical control settings that need to be considered are:

•

The temperature when the fan will begin to accelerate in response to the on-die thermal diode

temperature (T

LOW

)

•

The temperature where the fan speed is operating at full speed (100% PWM duty cycle). By

specification this is T

CONTROL

•

The minimum fan speed (PWM duty cycle). For any on-die thermal diode temperature less

than T

LOW

the fan will run at this speed

These are the minimum parameters required to implement acoustic fan speed control. See

Figure 18 for an example. There may be vendor specific options that offer enhanced functionality.

See the appropriate vendor datasheet on how to implement those features.

Section	Page
Contents	3
Figures	6
Tables	7
Revision History	8
1 Introduction	9
1.1 Document Goals and Scope	9
1.1.1 Importance of Thermal Management	9
1.1.2 Document Goals	9
1.1.3 Document Scope	10
1.2 References	11
1.3 Definition of Terms	12
2 Processor Thermal/Mechanical Information	15
2.1 Mechanical Requirements	15
2.1.1 Processor Package	15
2.1.2 Heatsink Attach	17
2.1.2.1 General Guidelines	17
2.1.2.2 Heatsink Clip Load Requirement	17
2.1.2.3 Additional Guidelines	18
2.2 Thermal Requirements	18
2.2.1 Processor Case Temperature	18
2.2.2 Thermal Profile	19
2.2.3 TCONTROL	20
2.3 Heatsink Design Considerations	21
2.3.1 Heatsink Size	22
2.3.2 Heatsink Mass	22
2.3.3 Package IHS Flatness	22
2.3.4 Thermal Interface Material	23
2.4 System Thermal Solution Considerations	23
2.4.1 Chassis Thermal Design Capabilities	23
2.4.2 Improving Chassis Thermal Performance	23
2.4.3 Summary	24
2.5 System Integration Considerations	24
3 Thermal Metrology	25
3.1 Characterizing Cooling Performance Requirements	25
3.1.1 Example	26
3.2 Processor Thermal Solution Performance Assessment	27
3.3 Local Ambient Temperature Measurement Guidelines	27
3.4 Processor Case Temperature Measurement Guidelines	30
4 Thermal Management Logic and Thermal Monitor Feature	31
4.1 Processor Power Dissipation	31
4.2 Thermal Monitor Implementation	31
4.2.1 PROCHOT# Signal	32
4.2.2 Thermal Control Circuit	32
4.2.3 Operation and Configuration	33
4.2.4 On-Demand Mode	34
4.2.5 System Considerations	34
4.2.6 Operating System and Application Software Considerations	35
4.2.7 On-Die Thermal Diode	35
4.2.7.1 Reading the On-Die Thermal Diode Interface	35
4.2.7.2 Correction Factors for the On-Die Thermal Diode	36
4.2.8 THERMTRIP# Signal	37
4.2.8.1 Cooling System Failure Warning	37
5 Intel® Thermal/Mechanical Reference Design Information	39
5.1 Intel Validation Criteria for the Reference Design	39
5.1.1 Heatsink Performance Target	39
5.1.2 Acoustics	40
5.1.3 Altitude	40
5.1.4 Reference Heatsink Thermal Validation	41
5.1.5 Fan Performance for Active Heatsink Thermal Solution	41
5.2 Environmental Reliability Testing	42
5.2.1 Structural Reliability Testing	42
5.2.1.1 Random Vibration Test Procedure	42
5.2.1.2 Shock Test Procedure	42
5.2.2 Power Cycling	44
5.2.3 Recommended BIOS/Processor/Memory Test Procedures	44
5.3 Material and Recycling Requirements	44
5.4 Safety Requirements	45
5.5 Geometric Envelope for ATX Intel® Reference Thermal Mechanical Design	45
5.6 ATX Reference Thermal Mechanical Solution for the Intel® Pentium® 4 Processor in the 775–Land LGA Package	46
5.7 Reference Attach Mechanism	48
5.7.1 Structural Design Strategy	48
5.7.2 Mechanical Interface to the Reference Attach Mechanism	49
6 Acoustic Fan Speed Control	53
6.1 Acoustic Fan Speed Control	53
6.2 Thermal Solution Design	53
6.2.1 Compliance to Thermal Profile	53
6.2.2 Determine Thermistor Set Points	53
6.2.3 Minimum Fan Speed Set Point	54
6.3 Board and System Implementation	55
6.3.1 Choosing Fan Speed Control Settings	55
6.3.1.1 Temperature to begin Fan Acceleration	56
6.3.1.2 Minimum PWM Duty Cycle	58
6.4 Combining Thermistor and Thermal Diode Control	59

Intel 640 User Guide - Page 55

Board and System Implementation

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