f75375 Feature Integration Technology Inc., f75375 Datasheet - Page 16

• Manufacturer Part Number: f75375
• Description: Fintek Hardware Monitor Ic Datasheet
• Manufacturer: Feature Integration Technology Inc.

mode, it generally acts as PWM fan speed control. As for speed mode and temperature mode, they are more
intelligent fan speed control and described as below:
Fan speed mode is an intelligent method according to expected fan speed pre-setting by BIOS.
will operate at full speed and the F75375S will get the full speed count value. Then fan speed slows down to rotate
at about 72.5% (8/11) of full speed. After that, the fan speed will automatically rotate according to the expected fan
speed setting by BIOS. The register CR74h and CR75h are used for this mode.
At this mode, F75375S provides the clever system to automatically control fan speed related to temperature of
GPU or the system. The F75375S can provide four temperature boundaries and five intervals, and each interval
has its related fan speed count. All these values should be set by BIOS first. Take figure 5-11 as example. When
temperature setting value is 45,55,65, and 75°C. There are five intervals and each interval is 10°C. The related
desired fan speed counts for each interval are 0500h, 0400h, 0300h, 0200h, 0100h. When the temperature is
within 55~65°C, the fan speed count 300h will be load into FAN EXPECT COUNTregisters(CR74h~CR75h,
CR84h~CR85h). Then, F75375S will adjust PWMOUT duty-cycle to make fan speed match the expected value. It
can be said that the fan will be turned on with a specific speed set by BIOS and automatically controlled with the
temperature varying. The F75375S will take charge of all the fan speed control and need no software support.
In both “FAN SPEED” and “TEMPERATURE” modes, F75375S adjust PWMOUT duty-cycle according to current
fan count and expected fan count. It will operate as follows:
6.3.2.1 Fan Speed mode
6.3.2.2 Temperature mode
6.3.2.3 PWMOUT Duty-cycle operating process
Fintek
75 Degree C
65 Degree C
55 Degree C
45 Degree C
Figure 5-11
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Feature Integration Technology Inc.
F75375S/F75375SG
Desired Counts
0100h
0200h
0300h
0400h
0500h
In the beginning, fan speed
July 2007
V0.26P