EMC2101-R-ACZL-TR datasheet(44/55 Pages) SMSC

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SMBus Fan Control with 1°C Accurate Temperature Monitoring

Datasheet

Revision 2.53 (03-13-07)

SMSC EMC2101

DATASHEET

Maximum resolution is achieved by setting the PWM Frequency Register to 1Fh. With maximum

resolution, the desired PWM frequency can be achieved by adjusting the PWM Frequency Divide

For example, if the user desires a 30Hz PWM frequency with maximum PWM resolution, then the

PWM_F[4:0] bits should be set at 1Fh (31d) and the the PWM_D bits should be set at C1h (193d).

6.21

Fan Control Look-Up Table Hysteresis Register

The Fan Control Look-Up Table Hysteresis Register determines the amount of hysteresis applied to

the temperature inputs of the fan control Fan Control Look-Up Table. See Section 5.6.4.

Where:

[5]

PWM_F is the setting of the PWM

Frequency register (4Dh)

PWM_D is the setting of the PWM

Frequency Divide Register (4Eh)

FREQ is the desired PWM

Frequency

Table 6.26 Examples of Fan PWM Frequency with Maximum Resolution

PWM_F[4:0] = 1Fh

PWM_D[7:0]

SETTING

EFFECTIVE

RESOLUTION

(%)

EFFECTIVE

DUTY CYCLE

(AT 50%

FAN_SETTING)

EFFECTIVE

DUTY CYCLE

(AT 75%

FAN_SETTING)

FAN_SETTING

TO GET 75%

DUTY CYCLE

EFFECTIVE PWM

FREQUENCY (HZ)

01h

1.61

51.6%

77.4%

2Eh (74.2%)

5806.5

11h

1.61

51.6%

77.4%

2Eh (74.2%)

341.6

20h

1.61

51.6%

77.4%

2Eh (74.2%)

181.5

47h

1.61

51.6%

77.4%

2Eh (74.2%)

81.8

1.61

51.6%

77.4%

2Eh (74.2%)

30.2

1.61

51.6%

77.4%

2Eh (74.2%)

30.0

FFh

1.61

51.6%

77.4%

2Eh (74.2%)

22.7

Table 6.27 Look Up Table Hysteresis Register

ADDR.

R/W

DEFAULT

4Fh

R/W

Fan Control Look-

Up Table Hysteresis

842

04h

(4°C)

PWM_D

360k

PWM_F

--------------------------------

⎝⎠

⎛⎞

FREQ

-----------------

5806

FREQ

-----------------

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