EMC2102 Standard Microsystems Corporation, EMC2102 Datasheet - Page 24

• Manufacturer Part Number: EMC2102
• Description: Rpm-based Fan Controller with HW Thermal Shutdown
• Manufacturer: Standard Microsystems Corporation

APPLICATION NOTE: When the device is operating in manual mode, the FAN_SPIN status bit may be set if the
Revision 1.95 (10-19-06)
Count = FFh
Prev Target
When the RPM based Fan Control Algorithm is running, the Spin Up Routine is initiated under the
following conditions:
1. The TACH Target Register value changes from a value of FFh to a value that is less than the Valid
2. At power-up if the FAN_MODE setting is ‘1’ or ‘open’ indicating 75% drive or 60% drive
3. The RPM based Fan Control Algorithm is started and the FAN_MODE setting is ‘0’ indicating 0%
4. The RPM based Fan Control Algorithm’s measured TACH count is greater than the Valid TACH
When the Spin Up Routine is operating, the fan driver is set to full scale for one quarter of the total
user defined spin up time. For the remaining spin up time, the fan driver output is set a a user defined
level (60% or 75% drive).
After the Spin Up Routine has finished, the EMC2102 measures the TACH. If the measured TACH
count is higher than the Valid TACH Count Register setting, the FAN_SPIN status bit is set and the
Spin Up Routine will automatically attempt to restart the fan.
Figure 5.3
based on the first condition above.
Target Count
Changed
TACH Count (see
respectively. If the FAN_MODE setting is ‘0’ indicating 0% drive, then the Spin Up Routine is not
initiated until another condition is met.
drive prior to algorithm control.
Count.
100%
fan drive is set at a level that is lower than the fan can operate (including zero drive). If the
FAN_SPIN interrupt is unmasked, then this condition will trigger an errant interrupt.
shows an example of the Spin Up Routine in response to a programmed fan speed change
¼ of Spin Up Time
Spin Up Time
Section 6.18
60% or 75%
New Target Count
Figure 5.3 Spin Up Routine
DATASHEET
and
Check TACH
Section
24
6.17).
Update Time
RPM-Based Fan Controller with HW Thermal Shutdown
Target Count
Reached
Fan Step
Algorithm controlled drive
SMSC EMC2102
Datasheet