W83791D Datasheet, PDF (29/46 Pages) Winbond – W83791D Winbond H/W Monitoring IC

W83791D
+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
FAN Out
GND
FAN
Connector
Pull-up resister
> 1K
Fan Input
Pin 18/19/20
3.9V Zener
W83791D
Figure 8-3. Fan with Tach Pull-Up to +12V
and Zener Clamp
+12V
+12V
FAN Out
GND
FAN
Connector
Preliminary
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
or totem-pole output
> 1K
Fan Input
Pin 18/19/20
3.9V Zener
W83791D
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 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 V alue} × 100%
255
22
Publication Release Date: Aug, 2001
Revision 0.41