EMC2104 datasheet(27/101 Pages) SMSC

27 / 101 page

Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown

Datasheet

SMSC EMC2104

Revision 1.74 (05-08-08)

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.

Figure 5.3 Fan Control Look-Up Table Example

Time

Fan

Setting

Temp

Averaged

Temperature

T4 - Hyst

T5 - Hyst

T6 - Hyst

T3 - Hyst

T2 - Hyst

Measurement taken

Fan

Setting

T7 - Hyst

T8 - Hyst

EMC2104 Fiches technique(PDF) 27 Page - SMSC Corporation