f75334 Feature Integration Technology Inc., f75334 Datasheet - Page 21

• Manufacturer Part Number: f75334
• Description: Performance Controller
• Manufacturer: Feature Integration Technology Inc.

Fan speed control mechanism
Manual mode
Temperature mode
Mode(Default) or manual duty 3. Manual RPM. More detail please refer register description.
represented as follows.
temperature variation of CPU/GPU or the system. The F75334DG 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 7-11 as example. When temperature
boundaries are set as 45, 55, 65, and 75°C and there are five intervals (each interval is 10°C).
The related desired fan speed counts for each interval are 0500h, 0400h, 0300h, 0200h and
0100h. When the temperature is within 55~65°C, the fan speed count 300h will be load into
FAN EXPECT COUNT that define in registers. Then, the F75334DG will adjust PWMOUT
duty-cycle to meet 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 variation. The
F75334DG will take charge of all the fan speed control and need no software support.
There are some modes to control fan speed and they are 1. Auto RPM Mode 2. Auto Duty
PWM Clock Input
For manual mode, it generally acts as software fan speed control.
At this mode, the F75334DG provides automatic fan speed control related to
G
Duty_cycle
D
S
R1
NMOS
+12V
R2
(%)
+
-
=
PNP Transistor
C
Programmed
FAN
14
Fig 7-10
8bit
255
PWM Clock Input
Register
Value
G
D
S
R1
NMOS
×
100
+5V
%
R2
+
-
PNP Transistor
F75334
C
July, 2007
FAN
V0.25P