AVR® 8-Bit RISC - Applications - Two-phase Brushless DC Motors

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Preferred over brushed motor because providing long life time, low level of electrical noise and low acoustic noise level.
Commonly using hall-sensors.

Typical applications:
- PC fans (CPU, GPU and PSU cooling)
- HVAC (domestic and industrial)

Sensor-based Control of Two-phase BLDC

Sensor input to interrupt pins.

Two hardware PWM channels controls driving transistor. Speed controlled by varying the PWM duty cycle.

Supported communication: TWI / SMBus. This eliminates need to adjust fan voltage to control the speed. Host sets speed, gets status/alarm and actual speed Stall detection and restart.

Target device: ATtiny25/45/85 family

Implementation example: ATtiny25/45/85: Perfect Match for PC Fan

Application Requirements:
- Two driver lines
- One Hall sensor input
- TWI Communication
- Alarm or Tacho (if TWI not used)
- Low Cost MCU

ATtiny25/45/85 Features:
- Two PWM channels
- IO pin with External Interrupt to read Hall sensor ADC channel to measure external speed reference input or current monitoring
- TWI Hardware support
- General I/O
- AVR is a low cost MCU

Document	Software	Description
		AVR441: Intelligent BLDC Fan Controller with Temperature Sensor and Serial Interface (26 pages, revision A, updated 09/05)
		AVR442: BLDC Fan Motor Control with ATtiny13 (10 pages, revision A, updated 09/05)

Sensorless Control of Two-phase BLDC

No hall sensor (Patent pending) reduces cost by $0.10 - $0.15

Hardware PWM based speed control
Stall detection and restart

Target device: ATtiny13, ATtiny25/45/85

Document	Software	Description
		AVR440: Sensorless Control of Two-Phase Brushless DC Motor (16 pages, revision A, updated 09/05)