Board Level PWM and Fan Speed Control Requirements
R
Thermal/Mechanical Design Guide
89
Table 8. ATX FSC Settings
Parameter Classification
Processor
Thermal Diode
PWM Output
Notes
T
HIGH
Required
T
CONTROL
3
T
LOW
Required
T
CONTROL
– 10 °C
3
Minimum PWM Duty
Cycle
Required
20%
PWM Frequency
Required
21–28
kHz
1
Spin-up time
Suggested
250 – ~500 ms
2
T
AVERAGING
Suggested
35
sec
When T
DIODE
< T
LOW
Suggested
Minimum
PWM%
All Fans ON
Suggested
T
CONTROL
+ 3 °C
Hysteresis Suggested
2
°C
NOTES:
1. A PWM output set to 25 kHz is the design target for the reference and for the Boxed Intel Processor and
the reference design.
2. Use the lowest time available in this range for the device selected.
3. To ensure compliance with the thermal specification, thermal profile and usage of the T
DIODE
for fan
speed control these setting should not be user configurable.
Table 9. Balanced Technology Extended
(
BTX) FSC Settings
Parameter Classificatio
n
Processor
Thermal Diode
System
Ambient Diode
PWM Output
Notes
T
HIGH
Required
T
CONTROL
54
°C
3,5
T
LOW
Required
T
CONTROL
– 7 °C
47 °C
3,5
Minimum PWM Duty
Cycle
Required
PWM 1 (TMA) -
20%
PWM Frequency
Required
21–28
kHz 1
Spin Up Time
Suggested
250 – ~ 500 ms
2
T
AVERAGING
Suggested
4.0 sec
4.0 sec
3
When T
DIODE
< T
LOW
Suggested
Minimum PWM%
Minimum PWM%
All Fans On
Suggested
T
CONTROL
+ 3 °C
65 °C
Hysteresis Suggested 2
°C 4
°C
NOTES:
1. A PWM frequency of 25 kHz is the design target for the reference and for the Intel
®
Boxed Processor
and the reference design.
2. Use the lowest time available in this range for the device selected
3. T
AVERAGEING
= represents the amount of delay time before responding to the temperature change, defined
in fan speed control device (sometimes called ramp range control or spike smoothing). Please select the
lowest setting available close to 4.0 seconds by the fan speed control device
4. The Fan Speed Controller, or Health Monitor Component, takes the result of the two fan speed ramps
(processor and system) and drives the TMA fan to the highest resulting PWM duty cycle (%)
5. For BTX systems, a second thermal sensor is recommended to capture chassis ambient temperature
(for more detail, see Appendix E).
6. To ensure compliance with the thermal specification, thermal profile and usage of the T
DIODE
for fan
speed control these setting should not be user configurable.
Summary of Contents for 640 - Pentium 4 640 3.2GHz 800MHz 2MB Socket 775 CPU
Page 14: ...Introduction R 14 Thermal Mechanical Design Guide ...
Page 38: ...Thermal Management Logic and Thermal Monitor Feature R 38 Thermal Mechanical Design Guide ...
Page 52: ...Intel Thermal Mechanical Reference Design Information R 52 Thermal Mechanical Design Guide ...
Page 60: ...Acoustic Fan Speed Control R 60 Thermal Mechanical Design Guide ...
Page 72: ...Heatsink Clip Load Metrology R 72 Thermal Mechanical Design Guide ...
Page 99: ...Mechanical Drawings R Thermal Mechanical Design Guide 99 Figure 50 Reference Fastener Sheet 1 ...
Page 103: ...Mechanical Drawings R Thermal Mechanical Design Guide 103 Figure 54 Clip Heatsink Assembly ...