W83697HF_05 Datasheet, PDF (29/102 Pages) Winbond – LPC I/O

W83697HF
6.4.2 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.
Duty − cycle(%) = ^{Programmed 8 - bit Register Value} × 100%
255
The PWM clock frequency also can be program and defined in the Bank0.CR5C . The application
circuit is shown as follows.
+12V
R1
R2
PWM Clock Input
D
G
NMOS
S
PNP Transistor
+
C
FAN
-
Figure 9.5
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