EMC2301 Standard Microsystems Corp., EMC2301 Datasheet - Page 30

• Manufacturer Part Number: EMC2301
• Description: Rpm-based Pwm Fan Controller
• Manufacturer: Standard Microsystems Corp.

ADDR
33h
Revision 1.2 (03-22-10)
5.10
0
0
1
1
R/W
R/W
1
EDGES[1:0]
2
0
0
0
0
1
1
1
1
Configuration 2
REGISTER
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.
Bit 2-0 - UPDATE[2:0] - 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 2 Register
0
1
0
1
Fan
0
Table
UPDATE[2:0]
5.13.
B7
MINIMUM TACH
-
1
0
0
1
1
0
0
1
1
Table 5.12 Minimum Edges for Fan Rotation
Table 5.14 Fan Configuration 2 Register
EDGES
3
5
7
9
RRC
EN_
B6
Table 5.13 Update Time
DATASHEET
GLITCH_
1 pole
2 poles (default)
3 poles
4 poles
NUMBER OF FAN POLES
EN
B5
30
0
0
1
0
1
0
1
0
1
DER_OPT [1:0]
B4
Table 5.12
B3
MULTIPLIER (BASED ON 2
ERR_RNG[1:0]
RPM-Based PWM Fan Controller
400ms (default)
UPDATE TIME
B2
is used as a direct multiplier
EFFECTIVE TACH
1200ms
1600ms
100ms
200ms
300ms
500ms
800ms
POLE FANS)
B1
0.5
1.5
1
2
SMSC EMC2301
Datasheet
B0
-
DEFAULT
28h