W83697HG Datasheet, PDF (30/109 Pages) Winbond – WINBOND LPC I/O

W83697HF/ HG
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
- 27 -
Publication Release Date: May 30, 2005
Revision A1