EMC6D103 datasheet(46/89 Pages) SMSC

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

Datasheet

Revision 0.4 (04-04-05)

SMSC EMC6D103

DATASHEET

Note 7.1

This max value will be FFFFh if the programmed number of edges is detected when the

count reaches FFFFh or if no edges are detected. If the count reaches FFFFh in Mode 1

and some edges were detected, but less than the programmed number of edges, the

maximum tach count value is determined by the Slow Interrupt Enable bit located in the

TACHx Options registers at offsets 90h to 93h. If slow interrupt detection is set to 0, the

count will be forced to FFFEh, else the count will be forced to FFFFh.

7.1.4.8

Examples of Minimum RPMs Supported

The following tables show minimum RPMs that can be supported with the different parameters. The

first table uses 3 edges and the second table uses 2 edges.

Note 7.2

100% duty cycle is 255/256.

Note 7.3

RPM=60/TRevolution, TTachPulse= TRevolution/2. Using 3 edges for detection, TTachPulse =

(PWM ”ON” Time – Guard Time). Minimum RPM values shown use minimum guard time

(88.88usec).

Table 7.2 Minimum RPM Detectable Using 3 Edges

PWM

FREQUENCY

PULSE WIDTH AT DUTY CYCLE

(PWM ”ON” TIME)

MINIMUM RPM AT DUTY CYCLE (Note 7.3)

(30/TTachPulse)

(HZ)

25%

(MSEC)

50%

(MSEC)

100%

(MSEC)

(Note 7.2)

25%

50%

100%

87.7

2.85

5.7

11.36

10865

5347

2662

58.6

4.27

8.53

7175

3554

1774

5.68

11.36

22.64

5366

2662

1330

35.2

7.1

14.2

28.3

4279

2126

1063

29.3

8.53

17.06

3554

1768

885

21.9

11.42

22.83

45.48

2648

1319

661

14.6

17.12

34.25

68.23

1761

878

440

22.73

45.45

90.55

1325

661

332

Table 7.3 Minimum RPM Detectable Using 2 Edges

PWM

FREQUENCY

PULSE WIDTH AT DUTY CYCLE

(PWM ”ON” TIME)

MINIMUM RPM AT DUTY CYCLE (Note 7.5)

(30/TTachPulse)

(HZ)

25%

(MSEC)

50%

(MSEC)

100%

(MSEC)

(Note 7.4)

25%

50%

100%

87.7

2.85

5.7

11.36

5433

2673

1331

58.6

4.27

8.53

3588

1777

887

5.68

11.36

22.64

2683

1331

665

35.2

7.1

14.2

28.3

2139

1063

532

29.3

8.53

17.06

1777

884

442

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