emc2104 Standard Microsystems Corp., emc2104 Datasheet - Page 66

• Manufacturer Part Number: emc2104
• Description: Emc2104 Dual Rpm-based Pwm Fan Controller With Hardware Thermal Shutdown
• Manufacturer: Standard Microsystems Corp.

Revision 1.74 (05-08-08)
0
0
1
1
1
EDGES[1:0]
2
0
0
0
0
1
1
1
1
term that is applied to the Actual RPM to achieve the Reported RPM. It should only be applied if the
number of edges measured does not match the number of edges expected based on the number of
poles of the fan (which is fixed for any given fan).
Contact SMSC for recommended settings when using fans with more or less than 2 poles.
Bit 2-0 - UPDATE - determines the base time between fan driver updates. The Update Time, along
with the Fan Step Register, is used to control the ramp rate of the drive response to provide a cleaner
transition of the actual fan operation as the desired fan speed changes. The Update Time is set as
shown in
0
1
0
1
0
Table
UPDATE[2:0]
6.31.
MINIMUM TACH
1
0
0
1
1
0
0
1
1
Table 6.30 Minimum Edges for Fan Rotation
EDGES
3
5
7
9
Table 6.31 Update Time
DATASHEET
Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
1 pole
2 poles (default)
3 poles
4 poles
NUMBER OF FAN POLES
66
0
0
1
0
1
0
1
0
1
MULTIPLIER (BASED ON 2
400ms (default)
UPDATE TIME
EFFECTIVE TACH
1200ms
1600ms
100ms
200ms
300ms
500ms
800ms
POLE FANS)
0.5
1.5
1
2
SMSC EMC2104
Datasheet