w83l784r Winbond Electronics Corp America, w83l784r Datasheet - Page 23

• Manufacturer Part Number: w83l784r
• Description: Winbond H/w Monitoring Ic
• Manufacturer: Winbond Electronics Corp America

6.5.3 Smart Fan Control
Fan Speed Cruise mode.
6.5.3.1 Thermal Cruise mode
automatically depend on current temperature to keep it with in a specific range. At first a wanted
temperature and interval must be set (ex. 55 C
remains below the setting value, the fan will be off. Once the temperature exceeds the setting high
limit temperature ( 58 C), the fan will be turned on with a specific speed set by BIOS (ex: 80% duty
cycle) and automatically controlled its PWM duty cycle with the temperature varying. Three
conditions may occur :
(1) If the temperature still exceeds the high limit (ex: 58 C), PWM duty cycle will increase slowly. If
the fan has been operating in its fully speed but the temperature still exceeds the high limit(ex: 58 C),
a warning message or a fan_fault signal(pin5) will be issued to protect the system.
(2) If the temperature goes below the high limit (ex: 58 C), but above the low limit (ex: 52 C), the fan
speed will be fixed at the current speed because the temperature is in the target area(ex: 52 C ~
58 C).
(3) If the temperature goes below the low limit (ex: 52 C), PWM duty cycle will decrease slowly to 0
until the temperature exceeds the low limit.
Figure 17 gives an illustration for Thermal Cruise Mode .
Confidential, For Beta-site Only
Smart Fan Control provides two mechanisms. One is Thermal Cruise mode and the other is
At this mode, W83L784R provides the Smart Fan system which can control the fan speed
PWM Clock Input
G
-22 -
Figure 16.
D
S
R1
NMOS
+5V
3 C) by BIOS, as long as the real temperature
R2
+
-
PNP Transistor
C
FAN
Publication Release Date: Sep.
W83L784R
Preliminary
Revision 0.54
1999