W83791G Datasheet, PDF (28/99 Pages) Winbond – Winbond H/W Monitoring IC

W83791D/G
+12V
+12V
FAN Out
GND
FAN
Connector
+5V
Pull-up resister
4.7K Ohms
Fan Input
Pin 18/19/20
W83791D
Figure 8-1. Fan with Tach Pull-Up to +5V
+12V
+12V
+12V
FAN Out
GND
FAN
Connector
Pull-up resister
4.7K Ohms
14K~39K
Fan Input
Pin 18/19/20
10K
W83791D
Figure 8-2. Fan with Tach Pull-Up to +12V, or Totem-Pole
Output and Register Attenuator
+12V
+12V
FAN Out
GND
FAN
Connector
Pull-up resister
> 1K
Fan Input
Pin 18/19/20
3.9V Zener
W83791D
+12V
FAN Out
GND
FAN
Connector
Pull-up resister < 1K
or totem-pole output
> 1K
Fan Input
Pin 18/19/20
3.9V Zener
W83791D
Figure 8-3. Fan with Tach Pull-Up to +12V
and Zener Clamp
Figure 8-4. Fan with Tach Pull-Up to +12V, or
Totem-Pole Putput and Zener Clamp
6.7.2 Fan speed control
The W83791D/G provides five sets of PWM for fan speed control. The duty cycle of PWM can be
programmed by a 8-bit registers defined in the Bank0 CR [81], CR [83], CR [94], CR [9E] and CR [9F].
The default duty cycle is set to 100%, that is, the default 8-bit register is set to 0xFFh. The expression
of duty cycle can be represented as follows.
Duty − cycle(%) = ^{Programmed 8 - bit Register Value} ×100%
255
+12V
PWM Clock Input
R1
R2
D
G
NMOS
S
PNP Transistor
+
C
-
FAN
Figure 9.
- 22 -
Publication Release Date: April 14, 2006
Revision 1.1