Electronic Design

High-Voltage, Two-Phase Gate Driver ICs

Sponsored by: NATIONAL SEMICONDUCTOR

What is a two-phase gate driver IC?

A two-phase gate driver IC is a power amplifier that produces two high-current gate drives for either a synchronous buck or half-bridge totem-pole MOSFET configuration. The two-phase driver provides the gate drive for both a low-side and high-side n-channel MOSFET. In contrast, the single-phase gate driver services only a single lowside MOSFET.

What is the function of the level shifter?

The level shifter must elevate the input voltage level to the appropriate range for the high-side driver. For best results, the level shifter must operate at high speeds while consuming low power and providing clean level translations.

How does the high-side driver support a high-voltage MOSFET?

Gate voltage for the high-side driver employs a bootstrap supply circuit comprising a bootstrap diode and bootstrap capacitor. The bootstrap diode may be either integrated within the gate driver IC or external to it. Because the bootstrap capacitor value must be much higher than the MOSFET gate capacitance, it is always external to the IC. When the lower MOSFET is enabled, the bootstrap capacitor charges up to VDD via the bootstrap diode. Thus, the high-side gate driver "floats" at the gate voltage of the high-side MOSFET. For reliable operation, the highside driver must be able to withstand the operating voltage of the high-side MOSFET. Typical maximum voltage ratings for high-voltage gate drivers can range from 80 to 100 V.

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