F81867 Datasheet, PDF (37/315 Pages) Feature Integration Technology Inc. – 6 UARTs μSuper IO With 128 Bytes FIFO and Power Saving Functions

DAC Fan Control
F81867
The range of DC output is 0~VCC, controlled by 8-bit register. 1 LSB is about 0.013V
(VCC=3.3V). 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:
Output_voltage (V) = VCC × ^{Programmed 8bit Register Value}
256
And the suggested application circuit for linear fan control would be:
DC OUTPUT VOLTAGE
+12V
R
3.6K
3₊
2_-
U1A
1
R
4.7K
PMOS
Q1
D1
1N4148
LM358
R 10K
JP1
C
47u
3
2
1
CON3
R
4.7K
R 27K
C
0.1u
R
10K
Fig 7-5
FANIN MONITOR
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.
Duty_cycle(%) = ^{Programmed 8bit Register Value} × 100%
255
+12V
R1
R2
GD
PNP Transistor
NMOS
S
+
C
-
FAN
Fig 7-6
37
Dec, 2011
V0.12P