W83697HF/F
9.4.2 Fan speed control
The W83697HF provides 2 sets for fan PWM speed control. The duty cycle of PWM can be programmed
by a 8-bit registers which are defined in the Bank0 CR5A and CR5B. 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.
Programmed 8 - bit Registe r V a l u e
Duty - c y c l e( % ) =
´ 1 0 0 %
2 5 5
The PWM clock frequency also can be program and defined in the Bank0.CR5C . The application circuit
is shown as follows.
+12V
R1
R2
PNP Transistor
D
G
PWM Clock Input
NMOS
S
+
-
C
FAN
Figure 9.5
Publication Release Date: Feb. 2002
Revision 0.70
- 90 -
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