EMC2104 Datasheet, PDF (27/101 Pages) SMSC Corporation – Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown

Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
Datasheet
to control the fan drive output independently (or jointly) by programming up to eight pairs of
temperature and drive setting entries.
The user programs the look-up table based on the desired operation. If the RPM based Fan Speed
Control Algorithm is to be used (see Section 5.5), then the user must program an RPM target for each
temperature setting of interest. Alternately, if the RPM based Fan Speed Control Algorithm is not to be
used, then the user must program a drive setting for each temperature setting of interest.
If the measured temperature on the External Diode channel meets or exceeds any of the temperature
thresholds for any of the temperature columns (see Appendix B), the fan output will be automatically
set to the desired setting corresponding to the exceeded temperature. In cases where multiple
temperature channel thresholds are exceeded, the highest fan drive setting will take precedence.
When the measured temperature drops to a point below a lower threshold minus the hysteresis value,
the fan output will be set to the corresponding lower set point.
Figure 5.3 shows an example of this operation using temperature - drive setting pairs for a single
channel.
See Appendix B for examples of the Look Up Table operation.
Temp
T8
T8 - Hyst
T7
T7 - Hyst
T6
T6 - Hyst
T5
T5 - Hyst
T4
T4 - Hyst
T3
T3 - Hyst
T2
T2 - Hyst
T1
SMSC EMC2104
Averaged
Temperature
Fan
Setting
Measurement taken
Time
Figure 5.3 Fan Control Look-Up Table Example
27
DATASHEET
Fan
Setting
S8
S7
S6
S5
S4
S3
S2
S1
Revision 1.74 (05-08-08)