W83697HFFDC Information Storage Devices, Inc, W83697HFFDC Datasheet - Page 99

• Manufacturer Part Number: W83697HFFDC
• Description: LPC Interface I/o Plus Game/midi Port, Fan Control, Flash ROM I/f
• Manufacturer: Information Storage Devices, Inc

9.4.2
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.
The PWM clock frequency also can be program and defined in the Bank0.CR5C . The application circuit
is shown as follows.
Fan speed control
D u t y
c y c l e
PWM Clock Input
( % )
P r o g r a m m e d 8 - b i t R e g i s te r V a l u e
G
D
S
R1
NMOS
Figure 9.5
- 90 -
+12V
R2
2 5 5
+
-
PNP Transistor
C
Publication Release Date: Feb. 2002
FAN
W83697HF/F
1 0 0 %
Revision 0.70