AN2839 Freescale Semiconductor / Motorola, AN2839 Datasheet - Page 3

• Manufacturer Part Number: AN2839
• Description: Implementing a Lamp Dimmer with an HC908Q Family MCU
• Manufacturer: Freescale Semiconductor / Motorola

during which the device is on is called the conduction angle (α). Varying α will control the portion of the
total AC sine wave applied to the load and, thereby, regulate the power flow to the load.
The main disadvantage of using phase control in triac applications is the generation of electro-magnetic
interference (EMI). In incandescent lamps, phase control gives a continuous brightness and good
performance.
HC908Q Family Features
High-performance 8-bit HC08 CPU:
Memory:
Peripherals:
Freescale Semiconductor
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Object-code compatible with Freescale’s 68HC05 architecture for easy migration
Enables the higher performance required of many 8-bit applications while saving development
time — as fast as 125 ns minimum instruction cycle time
Designed to allow efficient, compact modular coding in assembly or C with full 16-bit stack pointer
and stack relative addressing
Efficient instruction set with multiply and divide that is easy to learn and use
In-application, in-circuit re-programmable FLASH memory (1.5K to 4K bytes)
128 bytes of random access memory (RAM)
Two-channel, 16-bit timer with selectable input capture, output compare, or PWM
Trimmable 5% accuracy internal clock oscillator
Four-channel, 8-bit analog-to-digital converter (ADC) (on the MC68HC908QT2/QT4/QY2/QY4)
provides an easy interface to analog inputs such as sensors
Figure 1. Performing Power Control with Triac — Triggering the Device
Implementing a Lamp Dimmer with an HC908Q Family MCU, Rev. 0
a. Triac Symbol
G
MT2
MT1
Lamp
b. Sine Wave Showing Phase
Delay
angle
Control Principles
Conduction
angle
α
HC908Q Family Features
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