mc68hc908mr32 Freescale Semiconductor, Inc, mc68hc908mr32 Datasheet - Page 130

• Manufacturer Part Number: mc68hc908mr32
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Pulse-Width Modulator for Motor Control (PWMMC)
12.5.3 Top/Bottom Correction with Motor Phase Current Polarity Sensing
Ideally, when complementary pairs are used, the PWM pairs are inversions of each other, as shown in
Figure
voltage is never allowed to float and is strictly controlled by the PWM waveforms.
However, when dead-time is inserted, the motor voltage is allowed to float momentarily during the
dead-time interval, creating a distortion in the motor current waveform. This distortion is aggravated by
dissimilar turn-on and turn-off delays of each of the transistors.
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UP/DOWN COUNTER
12-18. When PWM1 is active, PWM2 is inactive, and vice versa. In this case, the motor terminal
MOUDULUS = 3
NO DEAD-TIME
NO DEAD-TIME
DEAD-TIME = 3
DEAD-TIME = 3
PWM1 W/
PWM2 W/
PWM1 W/
PWM2 W/
UP/DOWN COUNTER
PWM VALUE = 1
PWM VALUE = 2
PWM VALUE = 3
MODULUS = 4
PWM VALUE = 2
Figure 12-18. Ideal Complementary Operation (Dead-Time = 0)
PWM1
PWM2
PWM3
PWM4
PWM5
PWM6
Figure 12-17. Dead-Time and Small Pulse Widths
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
3
PWM VALUE = 3
3
PWM VALUE = 2
3
PWM VALUE = 1
3
Freescale Semiconductor
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