F81867 Datasheet, PDF (40/315 Pages) Feature Integration Technology Inc. – 6 UARTs μSuper IO With 128 Bytes FIFO and Power Saving Functions

F81867
There are two kinds for the auto modes they are the stage auto mode and the linear auto mode.
The “FAN1_INTERPOLATION_EN” in the register 0xAFh is used for the linear auto mode enable.
The following examples explain the differences for the stage auto mode and linear auto mode.
Stage auto mode
In this mode, the fan keeps in a same speed for each temperature interval. And there are two
types of fan speed setting: PWM Duty and RPM %.
A. Stage auto mode (PWM Duty)
Set the temperature limits as 70°C, 60°C, 50°C, 40°C and the duty as 100%, 90%, 80%, 70%, 60%
Fig 7-8 Stage mode fan control illustration
a.Once the temperature is under 40°C, the lowest fan speed keeps in the 60% PWM duty.
b.Once the temperature is over 40°C, 50°Cand 60°C, the fan speed will vary from 70%, 80% to 90%
PWM duty and increasing with the temperature level.
c. For the temperature higher than 70°C, the fan speed keeps in 100% PWM duty.
d.If set the hysteresis is 3°C (default 4°C), once the temperature becomes lower than 67°C, the fan
speed would reduce to 90% PWM duty.
B. Stage auto mode (RPM%)
Set the temperature as 70°C, 60°C, 50°C, 40°C and the corresponding fan speed is 6,000 RPM,
5,400 RPM, 4,800 RPM, 4,200 RPM, and 3,600 RPM (assume the Max Fan Speed is 6,000
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Dec, 2011
V0.12P