RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
Fan
Setting
Temp
T6
T6 - Hyst
S6
S5
T5
T5 - Hyst
T4
S4
T4 - Hyst
Averaged
Temperature
T3
S3
S2
Fan
Setting
T3 - Hyst
T2
T2 - Hyst
S1
Measurement taken
T1
Time
Figure 5.3 Fan Control Look-Up Table Example
5.4.1
Programming the Look Up Table
When the Look Up Table is used, it must be loaded and configured correctly based on the system
requirements. The following steps outline the procedure.
1. Determine whether the Look Up Table will drive a PWM duty cycle or a tachometer target value
and set the RPM / PWM bit in the Fan LUT Configuration Register (see Section 6.32).
2. Determine which measurement channels (up to four) are to be used with the Look Up Table and
set the TEMP3_CFG and TEMP4_CFG bits accordingly in the Fan LUT Configuration Register.
3. For each step to be used in the LUT, set the Fan Setting (either PWM or TACH Target as set by
the RPM / PWM bit). If a setting is not used, then set it to FFh (if a PWM) or 00h (if a TACH Target).
Load the lowest settings first in ascending order (i.e. Fan Setting 1 is the lowest setting greater
than “off”. Fan Setting 2 is the next highest setting, etc.). See Section 6.33.
4. For each step to be used in the LUT, set each of the measurement channel thresholds. These
values must be set in the same data format that the data is presented. If DTS is to be used, then
the format should be in temperature with a maximum threshold of 100°C (64h). If a measurement
channel is not used, then set the threshold at FFh.
5. Update the threshold hysteresis to be smaller than the smallest table step.
6. Configure the RPM based Fan Speed Control Algorithm if it is to be used. See Section 5.5.1 for
more details.
Revision 0.85 (01-29-08)
SMSC EMC2103
DATA2S6HEET
SMSC [ SMSC CORPORATION ]
