F71862
The range of DC output is 0~3.3V, controlled by 8-bit register. 1 LSB is about 0.013V.
The output DC voltage is amplified by external OP circuit, thus to reach maximum FAN
OPERATION VOLTAGE, 12V. The output voltage will be given as followed:
Programmed 8bit Register Value
Output_voltage (V) = 3.3×
255
And the suggested application circuit for linear fan 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
Fig 7-8
PWM duty Fan Control
The duty cycle of PWM can be programmed by a 8-bit register. 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.
Programmed8bit Register Value
Duty_cycle(%) =
×100%
255
+5V
+12V
R1
R1
R2
R2
PNP Transistor
PNP Transistor
D
D
G
G
PWM Clock Input
NMOS
PWM Clock Input
NMOS
S
+
-
S
+
-
C
C
FAN
FAN
Fig 7-9
Fan speed control mechanism
46
July, 2008
V.28P
FINTEK [ FEATURE INTEGRATION TECHNOLOGY INC. ]
