LM63 datasheet(29/44 Pages) TI2

29 / 44 page

100

_(%)

for

Value

PWM

Value

PWM

DutyCycle

LM63

www.ti.com

SNAS190E – SEPTEMBER 2002 – REVISED MAY 2013

APPLICATION NOTES

FAN CONTROL DUTY CYCLE VS. REGISTER SETTINGS AND FREQUENCY

ACTUAL

PWM

DUTY

PWM

STEP

FREQ AT

VALUE

CYCLE, %

FREQ

RESOLUTION,

360 kHz

1.4 kHz

4D [5:0]

4C [5:0] FOR

4C [5:0]

WHEN

4D [4:0]

INTERNAL

FOR 100%

ABOUT 75%

FOR 50%

75% IS

CLOCK, kHz

CLOCK, Hz

SELECTED

Address 0 is mapped to Address 1

180.0

703.1

50.0

90.00

351.6

75.0

16.7

60.00

234.4

83.3

12.5

45.00

175.8

75.0

10.0

36.00

140.6

80.0

8.33

30.00

117.2

75.0

7.14

25.71

100.4

78.6

6.25

22.50

87.9

75.0

5.56

20.00

78.1

77.8

5.00

18.00

70.3

75.0

4.54

16.36

63.9

77.27

4.16

15.00

58.6

75.00

3.85

13.85

54.1

76.92

3.57

12.86

50.2

75.00

3.33

12.00

46.9

76.67

3.13

11.25

43.9

75.00

2.94

10.59

41.4

76.47

2.78

10.00

39.1

75.00

2.63

9.47

37.0

76.32

2.50

9.00

35.2

75.00

2.38

8.57

33.5

76.19

2.27

8.18

32.0

75.00

2.17

7.82

30.6

76.09

2.08

7.50

29.3

75.00

2.00

7.20

28.1

76.00

1.92

6.92

27.0

75.00

1.85

6.67

26.0

75.93

1.79

6.42

25.1

75.00

1.72

6.21

24.2

75.86

1.67

6.00

23.4

75.00

1.61

5.81

22.7

75.81

COMPUTING DUTY CYCLES FOR A GIVEN FREQUENCY

Select a PWM Frequency from the first column corresponding to the desired actual frequency in columns 6 or 7.

Note the PWM Value for 100% Duty Cycle.

Find the Duty Cycle by taking the PWM Value of Register 4C and computing:

(1)

Example: For a PWM Frequency of 24, a PWM Value at 100% = 48 and PWM Value actual = 28, then the Duty

Cycle is (28/48) × 100% = 58.3%.

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