Single-Phase Full-Wave Motor Driver for Fan Motor # BA6908F Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The BA6908F is a 3-phase brushless DC motor driver IC primarily designed for precision motor control applications. Its typical implementations include:
- Fan Motor Control Systems : Provides efficient 3-phase driving for CPU cooling fans, power supply cooling fans, and industrial ventilation systems
- Small Appliance Motors : Used in compact household appliances requiring reliable brushless DC motor control
- Office Automation Equipment : Integrated into printers, scanners, and copiers for precise paper handling mechanisms
- Automotive Auxiliary Systems : Controls blower motors, water pumps, and small actuator systems in automotive environments
### Industry Applications
Consumer Electronics
- Computer peripherals (external hard drives, optical drives)
- Gaming console cooling systems
- Home entertainment equipment
Industrial Automation
- Small conveyor belt systems
- Precision positioning mechanisms
- Laboratory equipment motors
Automotive Sector
- HVAC blower motors
- Fuel pump controllers
- Window lift mechanisms
### Practical Advantages
Strengths:
- Integrated Design : Combines pre-driver, output stages, and protection circuits in single package
- Low Power Consumption : Typical operating current of 5mA in active mode
- Thermal Efficiency : Built-in thermal shutdown protection (typically 150°C)
- EMI Performance : Incorporates slew rate control for reduced electromagnetic interference
- Compact Footprint : SOP-24 package enables space-constrained designs
Limitations:
- Current Handling : Maximum output current of 1.2A may be insufficient for high-torque applications
- Voltage Range : Operating voltage 7-18V limits use in low-voltage or high-voltage systems
- Heat Dissipation : Requires adequate PCB thermal management at maximum current ratings
- Control Interface : Limited programmability compared to microcontroller-based solutions
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Inadequate Decoupling
- Issue : Motor noise coupling into power supply
- Solution : Implement 100nF ceramic capacitor close to VCC pin and 10μF electrolytic capacitor for bulk storage
Pitfall 2: Thermal Overload
- Issue : Excessive junction temperature during continuous operation
- Solution :
- Ensure proper copper pour for heat sinking
- Monitor case temperature during validation
- Consider external heatsink for high-duty cycle applications
Pitfall 3: Back-EMF Protection
- Issue : Voltage spikes during motor braking
- Solution : Implement flyback diodes and ensure proper PCB trace spacing
### Compatibility Issues
Microcontroller Interfaces
- Compatible with 3.3V and 5V logic levels
- Requires pull-up resistors for open-drain FG and RD outputs
- May need level shifting for 1.8V systems
Sensor Integration
- Designed for Hall sensor inputs (20kΩ typical input impedance)
- Compatible with most digital Hall effect sensors
- May require signal conditioning for analog sensors
Power Supply Considerations
- Stable 12V supply recommended for optimal performance
- Sensitive to power supply ripple >100mVpp
- Requires separate logic and motor power domains in noisy environments
### PCB Layout Recommendations
Power Stage Layout
- Use star grounding technique for power and signal grounds
- Keep high-current paths short and wide (minimum 2mm trace width for 1A)
- Place output capacitors within 10mm of IC pins
Signal Integrity
- Route Hall sensor signals away from motor outputs
- Use ground planes beneath sensitive analog sections
- Implement guard rings around FG and RD signals
Thermal Management
- Provide adequate copper area for heat dissipation (minimum 100mm²)
- Use thermal vias to distribute
