EMC2102 Standard Microsystems Corporation, EMC2102 Datasheet - Page 41

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

RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
SMSC EMC2102
6.13
52h
0
0
1
1
ADDRESS
1
EDGES[1:0]
The Fan Configuration Register controls the general operation of the RPM based Fan Control
Algorithm used for the High Side Fan Driver.
Bit 7 - EN - enables the RPM based Fan Control Algorithm.
Bit 6 - LIMIT2K - Adjusts the range of reported and programmed TACH count values.
Bit 4-3 - EDGES[1:0] - determines the minimum number of edges that must be detected on the TACH
signal to determine a single rotation. A typical fan measured 5 edges (for a 2-pole fan). For more
accurate TACH measurement, the minimum number of poles may be increased, however the TACH
measurement will be artificially higher than expected as denoted in the Effective TACH multiplier.
Additionally, some fans have more than 2-poles and therefore require more edges to be measured as
shown in the Number of Fan Poles
The EDGES[1:0] bits are shown in
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
Fan Configuration Register
FAN
Configuration
0
1
0
1
‘0’ - the control circuitry is disabled and the fan driver output is determined by the Fan Driver Setting
Register.
‘1’ (default) - the control circuitry is enabled and the Fan Driver output will be automatically updated
to maintain the programmed fan speed as indicated by the TACH Target Register.
‘0’ - the range of reported and programmable TACH values allows for a minimum speed of
approximately 500 RPM with reduced resolution to report lower speed values.
‘1’ (default) - the range of reported and programmable TACH values allows for a minimum speed
of approximately 2000 RPM with increased resolution to report higher speed values.
REGISTER
0
Table
6.19.
Table 6.17 Fan Control Configuration Register
MINIMUM TACH
EN
Table 6.18 Minimum Edges for Fan Rotation
B7
EDGES
3
5
7
9
LIMIT2K
B6
DATASHEET
Table
1 pole
2 poles (default)
3 poles
4 poles
-
NUMBER OF FAN POLES
B5
6.18.
41
EDGES[1:0]
B4
B3
UPDATE[2:0]
B2
MULTIPLIER (BASED ON 2
B1
EFFECTIVE TACH
POLE FANS)
Revision 1.95 (10-19-06)
B0
0.6
1.4
1.8
1
CBh
DEFAULT