AnalogySemi Gate Driver Selection and Application Guide
Gate drivers are critical components in power electronics, providing the interface between control circuits and power switches. This guide covers selection and application of AnalogySemi gate drivers.
Gate Driver Types
AnalogySemi offers several gate driver categories:
Isolated Gate Drivers like ANG6202 provide galvanic isolation between control and power circuits, essential for high-voltage applications.
Half-Bridge Drivers like ANG5100 drive high-side and low-side switches in half-bridge configurations with integrated bootstrap supply.
Low-Side Drivers are simple, non-isolated drivers for ground-referenced switches.
Key Selection Parameters
Isolation Voltage determines safety rating. For industrial equipment, 5kVrms reinforced isolation is typically required.
CMTI (Common Mode Transient Immunity) is critical for high-frequency switching. SiC applications require >50kV/μs.
Drive Current must be sufficient to charge/discharge MOSFET gate capacitance within required switching time.
SiC MOSFET Considerations
SiC MOSFETs require special gate drive considerations: Miller clamp to prevent false turn-on, negative gate voltage for reliable turn-off, and fast overcurrent protection.
Conclusion
Proper gate driver selection ensures reliable power switch operation. Consider isolation, CMTI, and drive current requirements for your specific application.
💡 FAE Insights
📋 Customer Cases
Power Systems Inc
Industrial Power
Challenge
Customer experienced intermittent shoot-through failures in their SiC-based converter. The gate driver was rated for the voltage but apparently couldn't handle the switching transients.
Solution
Replaced gate drivers with ANG6202 featuring 100kV/μs CMTI and added proper gate resistors to control switching speed. Implemented Miller clamp function.
Customer Feedback
"Shoot-through failures completely eliminated. System now operates reliably at full power. Customer was impressed by the CMTI explanation and its importance."
Frequently Asked Questions
1. What is CMTI and why is it important?
CMTI (Common Mode Transient Immunity) measures a gate driver's ability to maintain correct output state during rapid common-mode voltage transitions. During switching in half-bridge configurations, the high-side switch node experiences fast dv/dt transitions (up to 100kV/μs with SiC). Insufficient CMTI can cause the driver to output incorrect signals, leading to shoot-through. AnalogySemi ANG6202 offers 100kV/μs CMTI, suitable for SiC applications. Standard drivers with 50kV/μs may work for IGBTs but are marginal for SiC.
2. How do I calculate required gate drive current?
Gate drive current requirement: I_gate = Q_g / t_switch, where Q_g is total gate charge and t_switch is desired switching time. For example, SiC MOSFET with 100nC gate charge, target 50ns switching: I = 100nC / 50ns = 2A. Select driver with peak current rating > calculated value. Consider separate source and sink currents - higher sink current speeds up turn-off. AnalogySemi drivers range from 2A to 8A peak current.
3. When do I need isolated gate drivers?
Isolated gate drivers are required when: driving high-side switches with floating source (voltage above ground), safety isolation is needed between control and power circuits (industrial/medical equipment), high common-mode voltages exist (>100V), or noise immunity is critical. Non-isolated drivers can be used for low-side switches in low-voltage applications. AnalogySemi ANG6202 provides 5kVrms reinforced isolation suitable for industrial and medical applications.
4. What is Miller clamp and when do I need it?
Miller clamp prevents false turn-on caused by Miller capacitance coupling during high dv/dt switching. When the drain voltage rises rapidly, current flows through C_gd (Miller capacitance) and can raise gate voltage above threshold. Miller clamp provides low-impedance path to ground when gate is supposed to be off. Essential for SiC MOSFETs due to their high switching speed. ANG6202 integrates Miller clamp with 2A capability. For highest reliability with SiC, use Miller clamp even with negative gate voltage.
5. How do I set dead-time in half-bridge drivers?
Dead-time prevents shoot-through by ensuring both high-side and low-side switches are never on simultaneously. Set dead-time to 2-3x the MOSFET turn-off time. For MOSFETs with 100ns turn-off, use 200-300ns dead-time. ANG5100 uses external resistor: R_DT (kΩ) = (t_dead - 100ns) / 0.01. For 500ns dead-time: R = 40kΩ. Too little dead-time risks shoot-through; too much dead-time increases losses and output distortion. Always verify with oscilloscope measurement.