Holtek HT46R47 - 7+1 PWM Mode

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.
7+1 PWM Mode
Each full PWM cycle, as it is controlled by an 8-bit PWM register has 256 clock periods. However,
in the 7+1 PWM mode, each PWM cycle is subdivided into two individual sub-cycles, known as
modulation cycle 0 and modulation cycle 1, denoted as ²i² in the table. Each one of these two
sub-cycles contains 128 clock cycles. In this mode, a modulation frequency increase by a factor of
two is achieved. The 8-bit PWM register value, which represents the overall duty cycle of the PWM
waveform, is divided into two groups. The first group which consists of bit1~bit7 is denoted here as
the DC value. The second group which consists of bit0 is known as the AC value. In the 7+1 PWM
mode, the duty cycle value of each of the two modulation sub-cycles is shown in the following table.
Parameter AC (0~1) DC (Duty Cycle)
Modulation cycle i
(i=0~1)
i<AC
DC 1
128
+
i³AC
DC
128
7+1 Mode Modulation Cycle Values
44
A/D Type MCU
f
S Y S
/ 2
P W M
[ P W M ] = 1 0 0
[ P W M ] = 1 0 1
P W M
[ P W M ] = 1 0 2
P W M
[ P W M ] = 1 0 3
P W M
P W M c y c l e : 2 5 6 / f
S Y S
2 5 / 6 4
2 6 / 6 4
2 6 / 6 4
2 6 / 6 4
2 5 / 6 4 2 5 / 6 4 2 5 / 6 4
2 5 / 6 4
2 5 / 6 4
2 5 / 6 4
2 5 / 6 4
2 6 / 6 4
2 6 / 6 4
2 5 / 6 4
2 5 / 6 4
2 6 / 6 4 2 5 / 6 4
2 6 / 6 4
2 6 / 6 4
2 6 / 6 4
M o d u l a t i o n c y c l e 0
P W M m o d u l a t i o n p e r i o d : 6 4 / f
S Y S
M o d u l a t i o n c y c l e 1 M o d u l a t i o n c y c l e 2 M o d u l a t i o n c y c l e 3 M o d u l a t i o n c y c l e 0
6+2 PWM Mode
P W M R e g i s t e r ( 6 + 2 ) M o d e
b 7 b 0
A C v a l u e
D C v a l u e
PWM Register for 6+2 Mode