EMC2113 datasheet(28/85 Pages) SMSC

28 / 85 page

RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown

Datasheet

Revision 1.2 (10-08-09)

SMSC EMC2113

DATASHEET

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 6.6, "RPM-Based Fan Speed Control Algorithm (FSC)"),

then the user must program a fan speed 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 PWM

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 channels, 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. Figure 6.3, "Fan Control Look-Up

Table Example" shows an example of this behavior using a single channel.

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.

To turn the fan off, there are 2 methods:

The first is to set the Temps1-4 Setting 1 values (+ hysteresis) above the temperatures desired for

the fan to turn off. When the temperatures fall below Temps1-4 (out of the LUT) by the hysteresis

amount, the fan drive will be set to 0.

The second is to set the Drive 1 value to 0% (or 0RPM) as well as the Temp 1-4 values to the

temperatures (+ hysteresis) at which the fan should turn off. This method will reduce the effective

amount of fan drive settings to 7.

Figure 6.3 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

EMC2113 Datasheet(PDF) 28 Page - SMSC Corporation