AT90PWM2B-16SU View Datasheet(PDF) - Atmel Corporation
Part Name
Description
Manufacturer
AT90PWM2B-16SU
Atmel Corporation
AT90PWM2B-16SU Datasheet PDF : 365 Pages
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AT90PWM2/3/2B/3B
16.7.1
Frequency distribution
The frequency modulation is done by switching two frequencies in a 16 consecutive cycle frame.
These two frequencies are fb1 and fb2 where fb1 is the nearest base frequency above the wanted
frequency and fb2 is the nearest base frequency below the wanted frequency. The number of fb1
in the frame is (d-16) and the number of fb2 is d. The fb1 and fb2 frequencies are evenly distrib-
uted in the frame according to a predefined pattern. This pattern can be as given in the following
table or by any other implementation which give an equivalent evenly distribution.
Table 16-5. Distribution of fb2 in the modulated frame
Distribution of fb2 in the modulated frame
PWM - cycle
Fraction
al
Divider
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15
(d)
0
1
X
2
X
X
3
X
X
X
4
X
X
X
X
5
X
X
X
X
X
6
X
X
X
X
X
X
7
X
X
X
X
X
X
X
8
X
X
X
X
X
X
X
X
9
XXX
X
X
X
X
X
X
10
XXX
X
X
XXX
X
X
11
XXX
XXX
XXX
X
X
12
XXX
XXX
XXX
XXX
13
XXXXXXX
XXX
XXX
14
XXXXXXX
XXXXXXX
15
XXXXXXXXXXXXXXX
While ‘X’ in the table, fb2 prime to fb1 in cycle corresponding cycle.
So for each row, a number of fb2 take place of fb1.
Figure 16-12. Resulting Frequency versus d.
fb1
fb2
fOP
d: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
4317K–AVR–03/2013
143
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