W83791D Datasheet, PDF (31/46 Pages) Winbond – W83791D Winbond H/W Monitoring IC

W83791D
A
58`C
55`C
52`C
PWM ¹⁰⁰
Duty
Cycle ⁵⁰
Fan Start = 20%
0
B
C
Preliminary
D
Fan Stop = 10%
Fan Start = 20%
Figure 10-2.
6.7.3.2
Fan Speed Cruise mode
At this mode, W83791D provides the Smart Fan system to automatically control the fan speed within a
specific range. In the beginning, a wanted fan speed count and interval must be set (ex. 160± 10 ) by BIOS. As long
as the fan speed count remains in the specific range, PWM duty cycle will keep the current value. If current fan
speed count is higher than the high limit (ex. 160+10), PWM duty cycle will be increased to make the count under
the high limit. On the other hand, if current fan speed count is less than the low limit(ex. 160-10), PWM duty cycle
will be decreased to make the count higher than the low limit. See Figure 10-3 example.
A
Count
C
170
160
150
PWM ¹⁰⁰
Duty
Cycle ⁵⁰
0
Figure 10-3.
Of course, Smart Fan control system can be disabled and the fan speed control algorithm can be programmed by
BIOS or application software.
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Publication Release Date: Aug, 2001
Revision 0.41