3-Phase BLDCM + 6CH BTL Driver# Technical Documentation: FAN8741G High-Voltage Half-Bridge Gate Driver IC
Manufacturer : FAI (Fairchild Semiconductor / ON Semiconductor product family)
Document Version : 1.0
Last Updated : October 2023
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## 1. Application Scenarios
### 1.1 Typical Use Cases
The FAN8741G is a monolithic high-voltage, high-speed power MOSFET and IGBT driver designed for applications requiring high efficiency and robust switching performance. Its primary function is to drive the high-side and low-side N-channel power switches in half-bridge, full-bridge, or synchronous buck converter topologies.
Primary Use Cases Include:
* Switch-Mode Power Supplies (SMPS): Particularly in off-line AC-DC converters for desktop computers, servers, gaming consoles, and LCD TVs, where it drives the power stage in resonant LLC or asymmetric half-bridge (AHB) configurations.
* Motor Drive Circuits: Used in inverter stages for driving brushless DC (BLDC) motors and permanent magnet synchronous motors (PMSM) in appliances, fans, and light industrial equipment.
* DC-DC Converter Power Stages: Employed in high-power intermediate bus converters and point-of-load (POL) modules where a half-bridge topology is implemented.
* Lighting Ballasts: For driving the power switches in electronic ballasts for fluorescent and high-intensity discharge (HID) lamps.
* Solar Inverters: In the DC-AC conversion stage for small-scale string or micro-inverters.
### 1.2 Industry Applications
* Consumer Electronics: Power supplies for TVs, audio equipment, and desktop computers.
* Industrial Automation: Motor controllers for conveyor systems, pumps, and compact drives.
* Telecommunications: High-efficiency rectifiers and bus converters in server power supplies and telecom rectifiers.
* Renewable Energy: Power conversion stages in sub-1kW solar micro-inverters.
* Automotive (Aftermarket/Non-Safety Critical): High-power DC-DC converters for accessory power.
### 1.3 Practical Advantages and Limitations
Advantages:
* Integrated High-Voltage Level Shifter: The floating high-side driver can bootstrap to voltages exceeding 600V, simplifying high-side drive in bridge circuits without requiring an isolated power supply.
* Robustness: Features like under-voltage lockout (UVLO) for both VCC and VB-VS bootstrap supply, and a shutdown input enhance system reliability by preventing faulty operation during power anomalies.
* Fast Switching: Typical propagation delays of <100ns and matched delay times between HO and LO outputs minimize dead-time requirements and improve efficiency.
* Compact Solution: Integrating both drivers and logic into an 8-pin package (e.g., SOIC-8) reduces board space and component count compared to discrete solutions.
Limitations:
* Bootstrap Circuit Dependency: The high-side driver requires a properly designed bootstrap capacitor and diode. Continuous operation at very high duty cycles (>99%) can lead to bootstrap capacitor recharge issues.
* Peak Current Capability: While suitable for most MOSFETs and IGBTs, its peak source/sink current (typically ~200mA) may be insufficient for directly driving very large parallel MOSFET arrays or modules with extremely high gate charge (Qg) without an additional pre-driver stage.
* Limited Configuration Flexibility: As a dedicated half-bridge driver, it is less flexible than microcontroller-based or programmable driver solutions for complex multi-phase or multi-topology systems.
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## 2. Design Considerations
### 2.1 Common Design Pitfalls and Solutions
* Pitfall 1: Bootstrap Capacitor Undersizing.
* Symptom: High-side driver malfunctions or turns off
