Gen 4 GaN platform lowers conduction and switching losses

The semiconductor industry is still far from achieving the theoretical potential of gallium nitride (GaN) performance, says Jim Witham, CEO of GaN Systems. “It took silicon almost 20 years to go to second or third generation, so there are a lot of performance improvements that we’ll see in GaN technology,” he added. “It’s really about optimizing the chip performance, making it as small as possible while optimizing the packaging performance to get the heat out of device.”

Witham was talking to EDN on the launch of the company’s 4th generation GaN power platform operating at 700 V E-mode with a transient voltage rating of 850 V. GaN Systems is targeting these devices at power markets in consumer electronics, data centers, solar energy, industrial applications, and automotive.

According to Witham, with Gen 3 GaN devices in data centers, engineers were operating 3.2 kW power supplies and server racks at 100 W/in3 in 2022. “Gen 4 devices can achieve 120 W/in3 with efficiencies above Titanium levels.”

So, what has changed from Gen 3 to Gen 4 GaN devices? Witham says it’s a different chip that made changes on two fronts. First, it has refined fabrication steps on the process side. Second, on the design side, it has accomplished a 20% improvement in the figure of merit (FOM).

Explaining performance improvements, Witham said there are two key figures of merit. The first one is RDS(ON) times Qg.

FOM = RDS(on) x Qg

Here, RDS(ON), the drain-source on resistance, represents conduction losses, while Qg represents switching losses. Gen 4 devices bolster performance by minimizing switching and conduction losses. The second figure of merit is RDS(ON) times COSS (output capacitance), which amounts to connection losses times switching losses.

“It depends on your topology, which one you care more about,” Witham said. He added that compared to Gen 3, Gen 4 devices have a wider range of RDS(ON) levels and more increments between the different parts. “That allows us to offer four different kinds of packages.”

So, if a design engineer likes one package, say 8 x 8 PDFN, he or she could choose between three or four different parts to determine an optimum price/performance combination, and they are all interchangeable on the board.

The packaging options Gen 4 platform supports include PDFN, TOLL, TOLT, and Embedded. A wide range of packaging options combined with increased granularity in device specification enables correct RDS(ON) and package combinations for each application, optimizing electrical and thermal system performance.

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