F81867 Datasheet, PDF (44/315 Pages) Feature Integration Technology Inc. – 6 UARTs μSuper IO With 128 Bytes FIFO and Power Saving Functions

F81867
the F81867 starts to compare current fan count and expected count in order to increase or
decrease its duty-cycle. This ensures that if there is any glitch during the period, the
F81867 will ignore it.
Start Duty
Stop Duty
Fig 7-12
Fan Speed Control with Multi-temperature
F81867 supports Multi-temperature for Fan 1 control. Fan 1 can be controlled up to 2 kinds of
temperature inputs. This function works with linear auto mode which can extend to two linear slopes
for Fan 1 control. As below graph shows, this machine can support more silence fan control in low
temperature and high fan speed in the high temperature segment. More detail setting please refers to
the related registers.
RPM/PWM %
100%
90%
60%
40%
Slope can
be set
S=
ΔPWM/Δt =1
30ºC 50ºC
80ºC Temperature
Figure 7-13 Support 2 Linear Application with Multi-Temp. Setting
In the figure below, TFan1 is the scaled temperature for fan1. T1 is the real temperature for the
fan1 sensor. Ta is another temperature data which can be used for linearly scale up or scale down the
fan1 speed curve. Tb would be the point which starts the temperature scaling. The slope for the
temperature curve over and under Tb would be Ctup and Ctdn.
44
Dec, 2011
V0.12P