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Aug 16, 2023

Rohm integrates driver with GaN hemt to remove gate voltage woes

Rohm has co-packaged a gate driver and a 650V GaN power transistor to ease the design of power supplies in servers and ac adaptors. “While GaN hemts are expected to contribute to greater

Rohm has co-packaged a gate driver and a 650V GaN power transistor to ease the design of power supplies in servers and ac adaptors.

“While GaN hemts are expected to contribute to greater miniaturisation and improved power conversion efficiency, the difficulty in handling the gate compared to silicon mosfets requires the use of a dedicated gate driver,” according to the company. “In response, Rohm developed power stage ICs that integrate GaN hemts and gate drivers into a single package by leveraging core power and analogue technologies.”

There are two parts in the series so far, called BM3G0xxMUV-LB:

Both can accept a drive signal between 2.5 and 30V “enable compatibility with virtually any controller IC in primary power supplies, facilitating replacement of existing silicon super-junction mosfets”, said Rohm.

Power can come from 6.5 to 30V, and regulation for the gate voltage so critical to GaN hemts is taken care of by the IC.

Aside from on-resistance the two ICs are largely similar with, typically, quiescent current at 150-180µA, 12ns turn-on delay, 15ns turn-off delay, -40 to +105°C operation and 8 x 8 x 1mm VQFN packaging.

GaN transistors are fast enough to cause significant interference, so drive strength is resistor-programmable. “Generally, there is a trade-off between efficiency and EMI”, said Rohm. “A higher switching slew rate reduces the switching loss and, on the other hand, increases the switching noise. By adjusting the resistor, the turn-on slew rate can be selected freely from 28 to 100V/ns.”

Note: On resistance measured at 0.5A Id, 5Vin, 25°C ambient

At the same time, the company announced plans for similar ICs with different configurations: one for quasi-resonant ac-dc converters and another for power factor correction, both scheduled for mass production early in 2024, then, for Q2 2024, a half bridge. The first and last of these will include integrated X-capacitor dischargers.