RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
5.2
Fan Control Modes of Operation
The EMC2103 has four modes of operation for the fan driver. Each mode uses Ramp Rate control and
the Spin Up Routine
1. PWM Setting Mode - in this mode of operation, the user directly controls the PWM duty cycle
setting. Updating the Fan Driver Setting Register (see Section 6.20) will instantly update the fan
drive.
This is the default mode. The PWM Setting Mode is enabled by clearing both the EN_ALGO
bit in the Fan Configuration Register (see Section 6.22) and the LUT_LOCK bit in the Look
Up Table Configuration Register (see Section 6.32).
Whenever the PWM Setting Mode is enabled the current drive will be changed to what was
last written into the Fan Driver Setting Register.
2. Fan Speed Control Mode (FSC) - in this mode of operation, the user determines a fan speed and
the drive setting is automatically updated to achieve this target speed.
This mode is enabled by clearing the LUT_LOCK bit in the Look Up Table (LUT)
Configuration Register and setting the EN_ALGO bit in the Fan Configuration Register.
3. Using the Look Up Table with Fan Drive Settings (PWM Setting w/ LUT Mode) - In this mode of
operation, the user programs the Look Up Table with PWM duty cycle settings and corresponding
temperature thresholds. The fan drive is set based on the measured temperatures and the
corresponding drive settings.
This mode is enabled by programming the Look Up Table then setting the LUT_LOCK bit
while the RPM / PWM bit is set to a ‘1’ (see Section 6.32)
4. Using the Look Up Table with Fan Speed Control algorithm (FSC w/ LUT Mode)- In this mode of
operation, the user programs the Look Up Table with fan speed target values and corresponding
temperature thresholds. The TACH Target Register will be set based on the measured
temperatures and the corresponding target settings. The PWM drive settings will be determined
automatically based on the RPM based Fan Speed Control Algorithm
This mode is enabled by programming the Look Up Table then setting the LUT_LOCK bit
while the RPM / PWM bit is set to ‘0’ (see Section 6.32).
Table 5.3 Fan Controls Active for Operating Mode
DIRECT PWM
SETTING MODE
DIRECT PWM SETTING W/
LUT MODE
FSC MODE
FSC W/ LUT MODE
Fan Driver Setting (read
/ write)
Fan Driver Setting (read
only)
Fan Driver Setting (read only) Fan Driver Setting (read
only)
EDGES[1:0]
EDGES[1:0]
(Fan Configuration)
EDGES[1:0]
EDGES[1:0]
-
RANGE[1:0]
(Fan Configuration)
-
RANGE[1:0]
(Fan Configuration)
UPDATE[2:0]
(Fan Configuration)
UPDATE[2:0]
(Fan Configuration)
UPDATE[2:0]
(Fan Configuration)
UPDATE[2:0]
(Fan Configuration)
LEVEL
(Spin Up Configuration)
LEVEL
(Spin Up Configuration)
LEVEL
(Spin Up Configuration)
LEVEL
(Spin Up Configuration)
SPINUP_TIME[1:0]
(Spin Up Configuration)
SPINUP_TIME[1:0]
(Spin Up Configuration)
SPINUP_TIME[1:0]
(Spin Up Configuration)
SPINUP_TIME[1:0]
(Spin Up Configuration)
Fan Step
-
Fan Step
Fan Step
Fan Step
Fan Minimum Drive
Fan Minimum Drive
Revision 0.85 (01-29-08)
SMSC EMC2103
DATA2S4HEET
SMSC [ SMSC CORPORATION ]
