Pulse-Width Modulator for Motor Control (PWMMC)

UP/DOWN COUNTER

MOUDULUS = 3

PWM VALUE = 2

 

PWM VALUE = 3

PWM VALUE = 2

 

 

PWM VALUE = 1

 

 

 

 

 

 

 

 

 

 

PWM1 W/

NO DEAD-TIME

PWM2 W/

NO DEAD-TIME

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PWM1 W/

 

3

 

 

 

 

 

3

 

 

 

 

 

 

DEAD-TIME = 3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PWM2 W/

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

 

 

 

 

 

3

 

 

 

 

 

3

 

 

 

DEAD-TIME = 3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 12-17. Dead-Time and Small Pulse Widths

3

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 12-18. When PWM1 is active, PWM2 is inactive, and vice versa. In this case, the motor terminal voltage is never allowed to float and is strictly controlled by the PWM waveforms.

UP/DOWN COUNTER

MODULUS = 4

PWM1

PWM VALUE = 1

PWM2

PWM3

PWM VALUE = 2

PWM4

PWM5

PWM VALUE = 3

PWM6

Figure 12-18. Ideal Complementary Operation (Dead-Time = 0)

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.

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

130

Freescale Semiconductor

Page 129 Page 131
Page 130
Image 130
Freescale Semiconductor MC68HC908MR32, MC68HC908MR16 manual Dead-Time and Small Pulse Widths
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MC68HC908MR16, MC68HC908MR32 specifications

Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are part of the popular HC08 family, designed primarily for embedded applications. These microcontrollers are particularly favored in automotive, industrial, and consumer product sectors due to their reliability and versatility.

One of the standout features of the MC68HC908MR series is its CMOS technology, which enhances performance while minimizing power consumption. This makes these microcontrollers suitable for battery-operated devices. They operate at a maximum clock frequency of 2 MHz and offer a 16-bit architecture, providing a solid balance between processing power and efficiency.

The MC68HC908MR32 variant is equipped with 32KB of flash memory, which allows for the storage of complex programs and extensive data handling. In contrast, the MC68HC908MR16 features 16KB of flash memory, making it ideal for simpler applications. Both microcontrollers also come with 1KB of RAM, enabling efficient data processing and real-time operations.

Another significant characteristic of these microcontrollers is their integrated peripherals. They come with multiple input/output (I/O) pins, which allow for connectivity with various sensors and actuators. The built-in timer systems offer precise timing control for automotive and industrial applications, while the Analog-to-Digital Converter (ADC) provides essential conversion capabilities for various analog signals.

For communication purposes, the MC68HC908MR series includes a serial communication interface, enabling easy integration with other devices and systems. This versatility facilitates the development of complex systems that require interaction with external components.

Security is another crucial aspect of these microcontrollers. They have built-in fail-safe mechanisms to ensure reliable operation under various conditions, making them suitable for critical systems. Additionally, their robust architecture helps to safeguard against potential disruptions or attacks.

In summary, Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are key players in the embedded systems landscape. Their blend of power efficiency, integrated features, and scalability ensures they remain relevant for a wide array of applications, making them a favored choice among engineers and developers looking for dependable solutions in a competitive market.
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