PWM AND SECONDARY COMBO IC# Technical Documentation: FAN7585 Monolithic High-Voltage Half-Bridge Gate Driver IC
Manufacturer : FAIRCHILD (now part of ON Semiconductor)
Document Version : 1.0
Date : October 26, 2023
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## 1. Application Scenarios
### 1.1 Typical Use Cases
The FAN7585 is a monolithic high-voltage, high-speed power MOSFET and IGBT driver designed to operate with supply voltages up to 600V. 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 Applications Include:
* Motor Drive Systems: Controlling brushless DC (BLDC) motors and permanent magnet synchronous motors (PMSM) in appliances (e.g., washing machines, compressors) and light industrial equipment. It provides the necessary level-shifting to drive the high-side switch in a 3-phase inverter bridge.
* Switch-Mode Power Supplies (SMPS): Used in high-voltage half-bridge and full-bridge configurations for AC-DC power supplies (e.g., server PSUs, telecom rectifiers) and DC-DC converters, enabling efficient high-power conversion.
* Lighting Ballasts: Driving power switches in electronic ballasts for fluorescent lamps and high-intensity discharge (HID) lighting systems.
* Induction Heating: A key component in the resonant half-bridge inverters used in induction cooking tops and industrial heating systems.
### 1.2 Industry Applications
* Consumer Electronics: High-efficiency power supplies for TVs, gaming consoles, and audio amplifiers.
* Industrial Automation: Variable frequency drives (VFDs) for motor control in pumps, fans, and conveyor systems.
* Automotive: While not primarily an automotive-grade part, it finds use in auxiliary high-power systems and industrial vehicle applications requiring robust high-side switching.
* Renewable Energy: Inverter stages for small-scale solar micro-inverters or battery management system (BMS) power stages.
### 1.3 Practical Advantages and Limitations
Advantages:
* Integrated Bootstrap Functionality: The built-in high-voltage floating bootstrap diode simplifies the PCB design and reduces component count by eliminating the need for an external discrete diode.
* Wide Voltage Range: The high-side driver can operate with a bootstrap supply voltage (`VB`) up to 600V relative to ground, making it suitable for off-line (mains-powered) applications.
* Robustness: Features like under-voltage lockout (UVLO) for both the high-side and low-side drivers prevent power device operation at insufficient gate voltage, enhancing system reliability. It also has good noise immunity due to its level-shift circuit design.
* Matched Propagation Delays: The low-side and high-side channels have closely matched propagation delays (typically within 10ns), which is critical for preventing shoot-through currents in bridge topologies.
Limitations:
* Bootstrap Capacitor Dependency: The high-side driver's operational time is limited by the charge stored in the external bootstrap capacitor. This constrains the maximum allowable duty cycle for the high-side switch, especially at very low frequencies.
* Limited Peak Output Current: With a typical source/sink current capability of ±250 mA, it is suitable for driving MOSFETs and IGBTs with moderate gate charge. For driving very large parallel devices or modules with extremely high gate charge, an additional external buffer stage may be required.
* Fixed Dead Time: The IC itself does not provide programmable interlocking or dead time insertion. Dead time must be managed externally by the PWM controller to prevent shoot-through.
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## 2. Design Considerations
### 2.1 Common Design Pitfalls and Solutions
* Pitfall
