EMC6D103 datasheet(36/89 Pages) SMSC

36 / 89 page

Fan Control Device with High Frequency PWM Support and Hardware Monitoring Features

Datasheet

Revision 0.4 (04-04-05)

SMSC EMC6D103

DATASHEET

Figure 7.1 Automatic Fan Control Flow Diagram

*See Registers 5C-5Eh: PWM Configuration on page 65 for details.

When in Auto Fan Control Operating Mode the hardware controls the fans directly based on monitoring

of temperature and speed.

To control the fans:

Set the minimum temperature that will turn the fans on. This value is programmed in Registers 67h-

69h: Zone x Low Temp Limit (Auto Fan Mode Only).

The speed of the fan is controlled by the duty cycle set for that device. The duty cycle for the minimum

fan speed must be programmed in Registers 64h-66h: PWMx Minimum Duty Cycle. This value

corresponds to the speed of the fan when the temperature reading is equal to the minimum

temperature LIMIT setting. As the actual temperature increases and is above the Zone LIMIT

temperature and below the Absolute Temperature Limit, the PWM will be determined by a linear

function based on the Auto Fan Speed Range bits in Registers 5Fh-61h.

Auto Fan Mode

Initiated

Temp >=

AbsLimit

(69~6B)

Override all PWM

outputs to 100%

duty cycle except if

disabled or in

manual mode

Temp >= Limit

(66~68)

Temp >=

Hyst Temp

(6C~6D)

Set Fan Output to

Set fan output to

auto fan mode

minimum speed.

(63~65)

Yes

Fan Output

At 0%?

Yes

Fan Output

At 0%?

Yes

Set fan speed based on

Auto Fan Range

Algorithm*

Begin Fan Spin-Up

Yes

Set Fan Output to

100%

Fan Spinning Up?

Spin Up

Time Elapsed?

(5C-5E)

Yes

Begin Polling

Cycle

End Polling Cycle

End Fan Spin Up

Yes

Off/Min set to 1?

(62)

Yes

Set fan to min

PWM

Yes

EMC6D103 Datasheet(PDF) 36 Page - SMSC Corporation

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