Hardware Design

4.2.3 Microcontroller

The MC68HC908LB8 microcontroller is the core of the application. It processes the input and feedback signals and generates appropriate control signals. The description of the pins follows.

The inverter is controlled by signals on the TOP and BOT pins of the MCU.

Signal PWM0 is used to generate a sine wave. This signal (on comparator pin V+) is compared with the real current (on comparator pin V-) in the on-board comparator. The real current is sensed using the shunt resistor R4. The signal from PWM0 is filtered in the RC filter comprised of R30, R31 and capacitor C9.

The output of the comparator appears on pin VOUT.

The IRQ pin is used for the zero-crossing detection circuit and for entry to the monitor mode.

The microcontroller stage incorporates two header connectors, the Luminance Level connector and the Monitor Mode connector. The Luminance Level connector is used for the Luminance Level potentiometer (see Table 4-1). The Monitor Mode connector enables the MCU to enter the Monitor Mode. For Monitor Mode, the IRQ, OSC1, PTA0, and PTA1 pins are used (see Table 4-2).

The Fault LED is connected to pin PTA5; it indicates the actual state of the application.

DC-bus shift-down voltage is sensed on pin ADC2.

Real currents through tube1 and tube2 are sensed on pins ADC3 and ADC4. The tube voltage difference is sensed on pin ADC5.

In the discontinuous conduction mode HW variation, PWM1 pin is used directly for switching the PFC switch transistor (see Figure A-5). Comparator output is internally connected to the PWM fault pin. In the hysteresis current control mode HW variation, it is not used.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

30

Freescale Semiconductor

Page 29 Page 31
Page 30
Image 30
Freescale Semiconductor M68HC08 manual Microcontroller
Page 29 Page 31

M68HC08 specifications

Freescale Semiconductor, known for its innovative solutions in the field of embedded systems, developed the M68HC08 microcontroller family, which includes the MC68HC908QT2. This 8-bit microcontroller is engineered to meet the demands of diverse applications, including automotive, industrial, and consumer electronics.

The MC68HC908QT2 is designed around Freescale’s M68HC08 core, which is renowned for its efficient and reliable performance. This microcontroller integrates a powerful instruction set, enabling developers to create high-performance applications with relatively low power consumption. The device operates at a clock frequency of up to 3 MHz, which is adequate for various control tasks.

One of the key features of the MC68HC908QT2 is its memory architecture. It includes a 2 KB Flash memory for program storage, representing a significant advantage for developers requiring non-volatile memory. Additionally, it encompasses 128 bytes of EEPROM memory, allowing for data retention even after power loss. The microcontroller also has 256 bytes of RAM for efficient data manipulation during operation.

In terms of input/output capabilities, the MC68HC908QT2 supports a variety of interfacing options. The microcontroller features up to 20 general-purpose I/O pins for flexibility in connecting with peripheral devices. Additionally, it provides multiple analog-to-digital converters (ADC) and timers that facilitate efficient analog signal processing and precise control through timing functions.

The architecture of the MC68HC908QT2 also incorporates sophisticated on-chip peripherals, enhancing its functionality. These peripherals include PWM (Pulse Width Modulation) outputs, which are essential for applications requiring motor control and other precise duty cycle processes. The integrated watchdog timer ensures reliable operation by resetting the system in the event of an application failure.

Moreover, the MC68HC908QT2 is equipped with an efficient power management system, enabling operation in a low-power mode, ideal for battery-powered applications. This microcontroller is packaged in a compact 28-pin dual in-line package (DIP), making it suitable for space-constrained designs.

In summary, the Freescale Semiconductor MC68HC908QT2 microcontroller is distinguished by its robust performance, extensive memory options, and versatile I/O capabilities. Its advanced features, including built-in timers, ADC, and a power management system, make it an exceptional choice for developers seeking to implement reliable and efficient embedded solutions. With its comprehensive architecture, the MC68HC908QT2 remains a popular choice in the landscape of 8-bit microcontrollers.
Top Page Image Contents