DMOS FULL-BRIDGE PWM MOTOR DRIVER # A3959SLB Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The A3959SLB is a DMOS full-bridge PWM motor driver primarily designed for bidirectional control of DC motors and other inductive loads. Key applications include:
- Precision motor control systems requiring smooth operation at low speeds
- Positioning systems where accurate step control is essential
- Speed regulation applications demanding consistent torque output
- Bidirectional motor control in automated equipment
### Industry Applications
- Industrial Automation : Robotic arm joints, conveyor systems, and automated assembly line components
- Automotive Systems : Power window controls, seat positioning mechanisms, and mirror adjustment systems
- Medical Equipment : Precision pump controls, adjustable bed mechanisms, and diagnostic instrument positioning
- Consumer Electronics : Camera focus mechanisms, printer paper feed systems, and automated display adjustments
- Office Automation : Document feeder mechanisms, scanner positioning systems
### Practical Advantages
- High Current Capability : Sustains up to 2A continuous output current with 3A peak capability
- Thermal Efficiency : Internal DMOS power transistors minimize heat generation
- Voltage Flexibility : Operates from 12V to 50V supply range
- Protection Features : Integrated thermal shutdown, crossover current protection, and undervoltage lockout
- PWM Compatibility : Direct interface with microcontroller PWM outputs
### Limitations
- Heat Dissipation Requirements : Requires proper thermal management at maximum current ratings
- External Component Dependency : Needs external sense resistors for current limiting
- EMI Considerations : May require additional filtering in noise-sensitive applications
- Cost Consideration : Higher component cost compared to basic transistor-based drivers
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Inadequate Heat Management
- Problem : Overheating during continuous high-current operation
- Solution : Implement proper heatsinking and consider derating for elevated ambient temperatures
Pitfall 2: Ground Bounce Issues
- Problem : Noise coupling into sensitive control circuits
- Solution : Use star grounding and separate analog/digital ground planes
Pitfall 3: Insufficient Decoupling
- Problem : Voltage spikes affecting device performance
- Solution : Place 100nF ceramic and 10μF electrolytic capacitors close to power pins
Pitfall 4: Incorrect Sense Resistor Selection
- Problem : Inaccurate current limiting or excessive power dissipation
- Solution : Use low-inductance, high-power resistors with appropriate wattage rating
### Compatibility Issues
- Microcontroller Interface : Compatible with 3.3V and 5V logic levels
- Motor Types : Optimized for brushed DC motors; not suitable for brushless or stepper motors without additional circuitry
- Power Supply Requirements : Requires stable DC supply with low ripple; sensitive to voltage transients
- Sensor Integration : Compatible with Hall effect sensors and optical encoders for closed-loop control
### PCB Layout Recommendations
Power Section Layout
- Use wide copper traces for high-current paths (minimum 2mm width for 2A current)
- Place power components close to the IC to minimize trace inductance
- Implement separate ground planes for power and control sections
Thermal Management
- Provide adequate copper area for heat dissipation (minimum 2cm² of 2oz copper)
- Use thermal vias to transfer heat to inner layers or bottom side
- Consider external heatsink for continuous high-current applications
Signal Integrity
- Route control signals away from high-current paths
- Use ground planes beneath sensitive analog signals
- Keep PWM and phase control lines short and direct
Component Placement
- Position decoupling capacitors within 5mm of power pins
- Place sense resistors close to the
