EMC2301 Standard Microsystems Corp., EMC2301 Datasheet - Page 34

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

ADDR
38h
ADDR
37h
APPLICATION NOTE: The UPDATE bits and Fan Step Register settings operate independently of the RPM-based
APPLICATION NOTE: If the Fan Speed Control Algorithm is used, the default settings in the Fan Configuration 2
Revision 1.2 (03-22-10)
5.13
5.14
R/W
R/W
R/W
R/W
The Fan Max Step register, along with the Update Time, controls the ramp rate of the fan driver
response calculated by the RPM-based Fan Speed Control Algorithm. The value of the register
represents the maximum step size the fan driver will take between update times (see
When the FSC algorithm is enabled, Ramp Rate control is automatically used. When the FSC is not
active, then Ramp Rate control can be enabled by asserting the EN_RRC bit (see
The Fan Max Step register is software locked.
The Fan Minimum Drive register stores the minimum drive setting for the RPM-based Fan Speed
Control Algorithm. The RPM-based Fan Speed Control Algorithm will not drive the fan at a level lower
than the minimum drive unless the target Fan Speed is set at FFh (see
Fan Max Step Register
Fan Minimum Drive Register
1
0
0
1
1
Fan Minimum
REGISTER
Fan Max Step
Drive
REGISTER
Fan Speed Control Algorithm and will always limit the fan drive setting. That is, if the
programmed fan drive setting (either as determined by the RPM-based Fan Speed Control
Algorithm or by manual settings) exceeds the current fan drive setting by greater than the
Fan Step Register setting, the EMC2301 will limit the fan drive change to the value of the
Fan Step Register. It will use the Update Time to determine how often to update the drive
settings.
Register will cause the maximum fan step settings to be ignored.
SPINUP_TIME[1:0]
128
B7
Table 5.24 Minimum Fan Drive Register
B7
Table 5.23 Fan Max Step Register
-
B6
64
Table 5.22 Spin Time
B6
-
DATASHEET
0
0
1
0
1
B5
32
B5
32
34
B4
B4
16
16
B3
8
B3
8
B2
TOTAL SPIN UP TIME
4
B2
4
500 ms (default)
RPM-Based PWM Fan Controller
Section
250 ms
B1
1 sec
2 sec
2
B1
2
5.17).
Section
B0
1
B0
Section
SMSC EMC2301
1
5.10).
Datasheet
DEFAULT
5.9).
DEFAULT
10h
(40%)
66h