W83791D Information Storage Devices, Inc, W83791D Datasheet - Page 29

• Manufacturer Part Number: W83791D
• Description: Hardware Monitor With Speech Synthesizer And Asf Functions
• Manufacturer: Information Storage Devices, Inc

6.7.2 Fan speed control
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.
Figure 8-1. Fan with Tach Pull-Up to +5V
Figure 8-3. Fan with Tach Pull-Up to +12V
Connector
Connector
FAN
FAN
The W83791D provides five sets of PWM for fan speed control. The duty cycle of PWM can be programmed
FAN Out
FAN Out
and Zener Clamp
+12V
GND
+12V
GND
+12V
+12V
Duty
3.9V Zener
Pull-up resister
4.7K Ohms
Pull-up resister
+5V
Fan Input
cycle
Fan Input
> 1K
(% )
Pin 18/19/20
Pin 18/19/20
W83791D
W83791D
Programmed 8 - bit Register V alue
22
Connector
Connector
Figure 8-4. Fan with Tach Pull-Up to +12V, or
FAN
255
FAN
FAN Out
Figure 8-2. Fan with Tach Pull-Up to +12V, or Totem-Pole
FAN Out
+12V
GND
+12V
GND
Totem-Pole Putput and Zener Clamp
+12V
+12V
Output and Register Attenuator
Publication Release Date: Aug, 2001
Pull-up resister < 1K
or totem-pole output
Pull-up resister
4.7K Ohms
14K~39K
3.9V Zener
> 1K
100%
Fan Input
Fan Input
10K
W83791D
Preliminary
Revision 0.41
Pin 18/19/20
Pin 18/19/20
W83791D
W83791D