Datasheet

%100
%100___
_
_(%) u=
forValuePWM
ValuePWM
DutyCycle
LM63
www.ti.com SNAS190E –SEPTEMBER 2002–REVISED MAY 2013
APPLICATION NOTES
FAN CONTROL DUTY CYCLE VS. REGISTER SETTINGS AND FREQUENCY
ACTUAL
PWM PWM
PWM PWM PWM DUTY
PWM STEP FREQ AT FREQ AT
VALUE VALUE VALUE CYCLE, %
FREQ RESOLUTION, 360 kHz 1.4 kHz
4D [5:0] 4C [5:0] FOR 4C [5:0] WHEN
4D [4:0] % INTERNAL INTERNAL
FOR 100% ABOUT 75% FOR 50% 75% IS
CLOCK, kHz CLOCK, Hz
SELECTED
0 Address 0 is mapped to Address 1
1 50 2 1 1 180.0 703.1 50.0
2 25 4 3 2 90.00 351.6 75.0
3 16.7 6 5 3 60.00 234.4 83.3
4 12.5 8 6 4 45.00 175.8 75.0
5 10.0 10 8 5 36.00 140.6 80.0
6 8.33 12 9 6 30.00 117.2 75.0
7 7.14 14 11 7 25.71 100.4 78.6
8 6.25 16 12 8 22.50 87.9 75.0
9 5.56 18 14 9 20.00 78.1 77.8
10 5.00 20 15 10 18.00 70.3 75.0
11 4.54 22 17 11 16.36 63.9 77.27
12 4.16 24 18 12 15.00 58.6 75.00
13 3.85 26 20 13 13.85 54.1 76.92
14 3.57 28 21 14 12.86 50.2 75.00
15 3.33 30 23 15 12.00 46.9 76.67
16 3.13 32 24 16 11.25 43.9 75.00
17 2.94 34 26 17 10.59 41.4 76.47
18 2.78 36 27 18 10.00 39.1 75.00
19 2.63 38 29 19 9.47 37.0 76.32
20 2.50 40 30 20 9.00 35.2 75.00
21 2.38 42 32 21 8.57 33.5 76.19
22 2.27 44 33 22 8.18 32.0 75.00
23 2.17 46 35 23 7.82 30.6 76.09
24 2.08 48 36 24 7.50 29.3 75.00
25 2.00 50 38 25 7.20 28.1 76.00
26 1.92 52 39 26 6.92 27.0 75.00
27 1.85 54 41 27 6.67 26.0 75.93
28 1.79 56 42 28 6.42 25.1 75.00
29 1.72 58 44 29 6.21 24.2 75.86
30 1.67 60 45 30 6.00 23.4 75.00
31 1.61 62 47 31 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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