HT82A824R Datasheet, PDF (101/121 Pages) Holtek Semiconductor Inc – USB Audio MCU

HT82A824R
USB Audio MCU
PWM
Modulation Frequency
fSYS/64 for (6+2) bits mode
fSYS/128 for (7+1) bits mode
PWM Cycle
Frequency
fSYS/256
PWM Cycle
Duty
[PWM]/256
6+2 PWM Mode
Each full PWM cycle, as it is controlled by an 8-bit PWM0 or PWM1 register, has 256 clock
periods. However, in the 6+2 PWM Mode, each PWM cycle is subdivided into four individual sub-
cycles known as modulation cycle 0~modulation cycle 3, denoted as “i” in the table. Each one of
these four sub-cycles contains 64 clock cycles. In this mode, a modulation frequency increase by a
factor of four is achieved. The 8-bit PWM0 or PWM1 register value, which represents the overall
duty cycle of the PWM waveform, is divided into two groups. The first group which consists of
bit2~bit7 is denoted here as the DC value. The second group which consists of bit0~bit1 is known
as the AC value. In the 6+2 PWM mode, the duty cycle value of each of the four modulation sub-
cycles is shown in the following table.
Parameter
Modulation cycle i
(i=0~3)
AC (0~3)
i < AC
i ≥ AC
DC (Duty Cycle)
DC+1
64
DC
64
6+2 Mode Modulation Cycle Values
The following diagram illustrates the waveforms associated with the 6+2 mode of PWM operation.
It is important to note how the single PWM cycle is subdivided into 4 individual modulation cycles,
numbered from 0~3 and how the AC value is related to the PWM value.
fS Y S /2
[P W M ] = 1 0 0
PW M
2 5 /6 4
2 5 /6 4
2 5 /6 4
[P W M ] = 1 0 1
PW M
2 6 /6 4
2 5 /6 4
2 5 /6 4
[P W M ] = 1 0 2
PW M
2 6 /6 4
2 6 /6 4
2 5 /6 4
[P W M ] = 1 0 3
PW M
2 6 /6 4
2 6 /6 4
P W M m o d u la tio n p e r io d : 6 4 /fS Y S
M o d u la tio n c y c le 0
M o d u la tio n c y c le 1
2 6 /6 4
M o d u la tio n c y c le 2
P W M c y c le : 2 5 6 /fS Y S
2 5 /6 4
2 5 /6 4
2 5 /6 4
2 5 /6 4
M o d u la tio n c y c le 3
(6+2) PWM Mode Output Waveform
2 5 /6 4
2 6 /6 4
2 6 /6 4
2 6 /6 4
M o d u la tio n c y c le 0
b7
b0
P W M 0 /P W M 1 R e g is te r s (6 + 2 ) M o d e
A C v a lu e
D C v a lu e
Pulse Width Modulation Registers for (6+2) PWM Mode
Rev 1.00
101
April 14, 2011