Low Voltage/Low Saturation 2-CH DC Motor Driver# Technical Documentation: FAN8100N Half-Bridge Gate Driver IC
Manufacturer : FSC (Fairchild Semiconductor / ON Semiconductor)
## 1. Application Scenarios
### Typical Use Cases
The FAN8100N is a monolithic half-bridge gate driver IC designed to drive both high-side and low-side N-channel power MOSFETs or IGBTs in synchronous configurations. Its primary function is to provide high-current gate drive signals with appropriate dead-time control to prevent shoot-through currents.
Common implementations include:
- Motor Drive Circuits : Brushed DC motor H-bridge drivers, stepper motor controllers, and 3-phase BLDC motor inverters.
- Switch-Mode Power Supplies : Synchronous buck converters, half-bridge and full-bridge topologies in DC-DC conversion stages.
- Lighting Systems : High-intensity discharge (HID) lamp ballasts and LED driver circuits requiring high-side switching.
- Class D Audio Amplifiers : Output stage switching for efficient audio power amplification.
### Industry Applications
- Automotive : Electric power steering (EPS) systems, fuel pump controllers, and HVAC blower motor drives.
- Industrial Automation : Servo drives, conveyor belt motor controllers, and robotic actuator systems.
- Consumer Electronics : Desktop computer VRM (Voltage Regulator Module) circuits, gaming console power systems.
- Renewable Energy : Solar micro-inverters and battery management system (BMS) balancing circuits.
### Practical Advantages and Limitations
Advantages:
- Integrated Bootstrap Function : Simplifies high-side drive by eliminating the need for isolated power supplies through built-in bootstrap diode.
- Shoot-Through Protection : Internal dead-time control (typically 520ns) prevents simultaneous conduction of high-side and low-side switches.
- Wide Voltage Range : Operates with supply voltages from 10V to 20V, compatible with common 12V systems.
- High Drive Capability : Peak output current of ±1.5A enables fast switching of power MOSFETs, reducing switching losses.
- Compact Solution : 8-pin SOP package minimizes board space compared to discrete driver implementations.
Limitations:
- Fixed Dead Time : The internal dead time cannot be adjusted, which may not be optimal for all switching frequencies or MOSFET characteristics.
- Limited Current Drive : For very high-power applications with large gate charge MOSFETs, external buffer stages may be required.
- Temperature Constraints : Maximum junction temperature of 150°C may require thermal management in high-ambient environments.
- Bootstrap Limitations : Minimum duty cycle requirements exist to maintain bootstrap capacitor charge for continuous high-side operation.
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Bootstrap Circuit Under-Voltage
- Problem : Inadequate bootstrap capacitor sizing or excessive duty cycles can discharge the bootstrap capacitor, causing high-side drive failure.
- Solution : Calculate bootstrap capacitor using formula Cboot ≥ (Qg_total × 10) / ΔVboot, where Qg_total is total gate charge and ΔVboot is allowable voltage droop (typically 0.5V). Add margin (20-50%) for reliability.
Pitfall 2: Ground Bounce and Noise Coupling
- Problem : High di/dt switching currents can induce voltage spikes in ground paths, causing false triggering.
- Solution : Implement star grounding at the IC's GND pin, separate power and signal grounds, and use low-ESR/ESL decoupling capacitors close to the IC.
Pitfall 3: Excessive Ringing at Switch Nodes
- Problem : Parasitic inductance in switching loops causes voltage overshoot that can exceed MOSFET ratings.
- Solution : Minimize loop area in high-current paths, use snubber circuits (RC or RCD), and select MOSFETs with appropriate voltage ratings
