Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
Datasheet
Set TACH Target
Count
Measure Fan Speed
Spin Up
Required
?
Yes
Perform Spin Up
Routine
No
TACH
Reading =
TACH
Yes
Maintain Fan Drive
Target?
No
TACH
Reading <
TACH
Ramp Rate Control
No
Yes
Target?
Reduce Fan Drive
Increase Fan Drive
Figure 5.4 RPM based Fan Speed Control Algorithm
Revision 1.74 (05-08-08)
SMSC EMC2104
DATA3S0HEET