RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown
Datasheet
Table 6.2 TRIP_SET Resistor Setting (continued)
TTRIP (°C)
RSET (1%)
TTRIP (°C)
RSET (1%)
94
95
96
1020
1100
1150
126
127
65
29400
49900
Open
6.2
Fan Control Modes of Operation
The EMC2113 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 7.22, "Fan Setting Registers") will
instantly update the fan drive. The driver uses the Spin Up Routine and has user definable ramp
rate controls.
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 7.24) and the LUT_LOCK bit in the Look
Up Table Configuration Register (see Section 7.34).
Whenever the PWM Setting Mode is enabled, the current drive will be changed to what was
last written into the Fan Driver Setting Register.
The Ramp Rate is controlled by the settings of the Max Step register (see Section 7.28) and
Update Period controls (Section 7.24) and must be enabled via the EN_RRC bit (see
Section 7.25).
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. The algorithm uses the Spin
Up Routine and has user definable ramp rate controls.
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. The fan driver uses the Spin Up Routine and has user definable ramp
rate controls.
This mode is enabled by programming the Look Up Table then setting the LUT_LOCK bit
while the EN_ALGO bit is set to ‘0’.
The RPM / PWM bit in the Look Up Table Configuration Register MUST be set to ‘1’ or the
PWM drive settings will be incorrectly set.
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. 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 EN_ALGO bit is set to ‘1’.
The RPM / PWM bit in the Look Up Table Configuration Register MUST be set to ‘0’ or the
TACH Target values will be incorrectly set.
APPLICATION NOTE: It is important that the TACH Target settings are in the proper format when using the RPM-
based Fan Speed Control Algorithm.
Revision 1.2 (10-08-09)
SMSC EMC2113
DATA2S6HEET
SMSC [ SMSC CORPORATION ]
