F71872
Programmed8 - bit Register Value
255
Output_voltage (V) = 3.3×
And the suggested application circuit for linear fac control would be:
12V
3
2
PMOS
+
-
1
DC OUTPUT VOLTAGE
D1
LM358
1N4148
R
4.7K
JP1
FANIN MONITOR
R 27K
3
R 10K
C
47u
2
1
C
0.1u
R
10K
CON3
R
3.9K
DC FAN Control with OP
PWM duty Fan Control
The duty cycle of PWM can be programmed by a 8-bit register which are defined in the CR6Bh, CR7Bh
and CR8Bh. The default duty cycle is set to 100%, that is, the default 8-bit registers is set to FFh. The
expression of duty can be represented as follows.
Programmed8 - bit Register Value
Duty_cycle(%) =
×100%
255
+5V
+12V
R1
R1
R2
R2
PNP Transistor
PNP Transistor
D
G
D
G
PWM Clock Input
NMOS
PWM Clock Input
NMOS
S
+
-
S
+
-
C
C
FAN
FAN
6.4.5 Fan speed control mechanism
There are 3 modes to control fan speed and they are manual, fan speed mode and temperature mode.
For manual 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:
20
July, 2007
V0.28P
FINTEK [ FEATURE INTEGRATION TECHNOLOGY INC. ]
