Maxim Integrated DS4830A Optical Microcontroller User Manual
Page 128
DS4830A User’s Guide
128
Table 14-2: Number of Slots for Each Resolution
RES_SEL[3:0]
Resolution
PS[1:0]= 00
PS[1:0]= 01
PS[1:0]= 10
PS[1:0]= 11
Number of Slots
0000b
7
1
1
1
1
0001b
8
1
1
1
2
0010b
9
1
1
2
4
0011b
10
1
2
4
8
0100b
11
2
4
8
16
0101b
12
4
8
16
32
0110b
13
8
16
32
64
0111b
14
16
32
64
128
1000b
15
32
64
128
256
1001b
16
64
128
256
512
>1001b
16
64
128
256
512
Pulse Spreading Method
The DS4830A PWM controller uses a delta sigma algorithm to distribute the duty cycle uniformly among the slots.
For example, a 10-bit PWM output with a DCYCn value of 128 with 8-slot pulse spreading enabled (PS[1:0] = b’11)
produces a PWM output as shown in the Figure 14-5. The duty cycle of 128 in 1024 cycles (10-bit resolution) has
been divided over 8 equal slots of 16 PWM clock cycles. As duty cycle increases by a count each time the pulse
spread is implemented uniformly and the corresponding duty cycle is distributed among slots. Table 14-3 and Figure
14-5 explain this example. Example considers PWM operation in the positive polarity.
Table 14-3: Duty Cycle Distribution with 8-Slot Pulse Spreading for 10-Bit Resolution PWM Operation
Resolution
Duty
Cycle
Slot 1
Slot 2
Slot 3
Slot 4
Slot 5
Slot 6
Slot 7
Slot 8
10
128
16
16
16
16
16
16
16
16
129
16
16
16
16
16
16
16
17
130
16
16
16
17
16
16
16
17
131
16
16
17
16
16
17
16
17
132
16
17
16
17
16
17
16
17
133
16
17
16
17
17
16
17
17
134
16
17
17
17
17
16
17
17
135
16
17
17
17
17
17
17
17
136
17
17
17
17
17
17
17
17