SMSC EMC2102 User Manual
Fan Speed Control with the EMC2102 Device
SMSC EMC2102
USER MANUAL
Revision 0.2 (09-17-07)
29
If the fan is already set to 75% level, we will need to lower the valid speed (function of 56h, Valid
TACH) to a value below the rpm75, to fix the problem.
TACH) to a value below the rpm75, to fix the problem.
To test this situation, set spin-up level to 75% (53h[2] = 1), set the Valid TACH Count (56h) = 6000
rpm and then start the fan (57h) with 6500 rpm. The spin-up routine will run repeatedly.
rpm and then start the fan (57h) with 6500 rpm. The spin-up routine will run repeatedly.
Change the Valid TACH Count (56h) to 5800 rpm, the problem cannot be fixed since the valid speed
is still higher than the fan speed (rpm75 = 5650 rpm).
is still higher than the fan speed (rpm75 = 5650 rpm).
Set 56h = 5580 rpm which is below 5650 rpm (the rpm75), the system gets out of the spin-up routine
(
(
Figure 5.24 Theoretical Plot of Case 1
Figure 5.25 Spin-up Case 1 Fix 1
RPM for
100% Drive
rpm60 or rpm75
Spin Up Time
¼ of Spin Up Time
Valid Speed
Check TACH
Fan Speed
(RPM)
Target Speed
Fan Speed
Spin Up Level
Changed to 75%