2-Channel High Side Only Gate Driver# Technical Documentation: FAN7385 High-Voltage Half-Bridge Gate Driver IC
Manufacturer : FAI (Fairchild Semiconductor / ON Semiconductor lineage)
Component Type : Monolithic High-Voltage, High-Speed Gate Driver IC
Primary Function : Drives both high-side and low-side N-Channel power MOSFETs or IGBTs in a half-bridge configuration.
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## 1. Application Scenarios
### Typical Use Cases
The FAN7385 is specifically engineered for high-voltage, high-frequency switching applications requiring robust and efficient control of power switches. Its integrated high-side driver uses a bootstrap circuit, eliminating the need for an isolated power supply. Key use cases include:
* Motor Drive Inverters : Controlling 3-phase AC induction motors (ACIM) and brushless DC (BLDC) motors in variable frequency drives (VFDs). It provides the necessary level-shifting and dead-time control to prevent shoot-through currents.
* Switch-Mode Power Supplies (SMPS) : Used in high-power, high-efficiency topologies like half-bridge and full-bridge converters for server PSUs, telecom rectifiers, and welding power supplies.
* Uninterruptible Power Supplies (UPS) : Drives the inverter stage that converts DC battery power to clean AC output.
* Solar Inverters : In the DC-AC conversion stage of micro-inverters and string inverters.
* Induction Heating & Lighting : Controls resonant half-bridge circuits for consumer and industrial induction cooktops and electronic ballasts.
### Industry Applications
* Industrial Automation : Spindle drives, conveyor systems, robotic arms.
* Consumer Appliances : Inverter-based air conditioners, washing machines, refrigerator compressors.
* Renewable Energy : Photovoltaic inverter systems.
* Automotive : Emerging in auxiliary drives and high-voltage systems in electric vehicles (xEVs).
### Practical Advantages and Limitations
Advantages:
* High Voltage Capability : Floating high-side channel can withstand up to +600V (FAN7385), suitable for direct off-line (e.g., 400V DC bus) applications.
* Integrated Functionality : Combines a high-voltage level shifter, bootstrap diode, and two independent drivers in one package, reducing component count and board space.
* Robust Protection : Features under-voltage lockout (UVLO) for both VCC and VB-VS (high-side supply), preventing power device operation at insufficient gate voltage.
* Matched Propagation Delays : Minimizes distortion in output waveforms, crucial for motor control and high-frequency power conversion.
* High Sink/Source Current : Capable of sourcing/sinking ±2.5A peak current, enabling fast switching of large MOSFET/IGBTs to reduce switching losses.
Limitations:
* Bootstrap Circuit Dependency : The high-side drive requires a bootstrap capacitor. This limits the maximum duty cycle for the high-side switch, as the capacitor must be periodically recharged when the low-side switch is on.
* dv/dt Immunity : While designed for high noise immunity, extremely high dv/dt transients on the switch node (VS pin) can cause parasitic turn-on or latch-up if layout is poor.
* Limited High-Side On-Time : For DC operation (100% duty cycle), the bootstrap capacitor will discharge due to leakage, requiring an auxiliary charge pump or an isolated power supply.
* Single Half-Bridge : Drives only one phase leg. Multi-phase systems (e.g., 3-phase motor drives) require multiple ICs.
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## 2. Design Considerations
### Common Design Pitfalls and Solutions
1. Shoot-Through Current (Cross-Conduction):
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