EMC2103-2-AP-TR Standard Microsystems (SMSC), EMC2103-2-AP-TR Datasheet - Page 56

• Manufacturer Part Number: EMC2103-2-AP-TR
• Description: CLOSED LOOP RPM FAN CONTROLLER
• Manufacturer: Standard Microsystems (SMSC)

Revision 0.88 (06-30-08)
0
0
1
1
1
EDGES[1:0]
The Fan Configuration 1 Register controls the general operation of the RPM based Fan Speed Control
Algorithm used on the PWM pin.
Bit 7 - EN_ALGO - enables the RPM based Fan Speed Control Algorithm. Based on the setting of the
RPM / PWM bit, this bit is automatically set or cleared when the LUT_LOCK bit is set (see
Section
Bits 6- 5 - RANGE[1:0] - Adjusts the range of reported and programmed tachometer reading values.
The RANGE bits determine the weighting of all TACH values (including the Valid TACH Count, TACH
Target, and TACH reading) as shown in
Bits 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 tachometer measurement, the minimum number of edges measured may be increased.
Increasing the number of edges measured with respect to the number of poles of the fan will cause
the TACH Reading registers to indicate a fan speed that is higher or lower than the actual speed. In
order for the FSC Algorithm to operate correctly, the TACH Target must be updated by the user to
accommodate this shift. The Effective Tach Multiplier shown in
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.
1
0
0
1
1
0
1
0
1
‘0’ - (default) the control circuitry is disabled and the fan driver output is determined by the Fan
Driver Setting Register.
‘1’ - 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.
6.32).
0
RANGE[1:0]
MINIMUM TACH
Table 6.32 Minimum Edges for Fan Rotation
EDGES
3
5
7
9
Table 6.31 Range Decode
0
0
1
0
1
DATASHEET
1 pole
2 poles (default)
3 poles
4 poles
NUMBER OF FAN POLES
Table
56
6.31.
REPORTED MINIMUM
RPM-Based Fan Controller with HW Thermal Shutdown
1000 (default)
RPM
2000
4000
500
Table 6.32
MULTIPLIER (BASED ON 2
is used as a direct multiplier
EFFECTIVE TACH
POLE FANS)
TACH COUNT
MULTIPLIER
0.5
1.5
1
2
SMSC EMC2103
1
2
4
8
Datasheet