Page 35 - PEN eBook May 2023

SEMICONDUCTORS SEMICONDUCTORS

As shown in Figure 6(a), a V DS(TR) ringing voltage is
also specified. In this case, V DS(TR) is 800 V, giving an
80-V headroom over the V DS(SURGE) rating.
In Figure 6(b), the device surge curves are shown
as it is powering a 1-kW load. In this case, 50
surge strikes were used, and there was no loss of
efficiency, demonstrating surge robustness.Further,
the LMG341x parts have built-in short-circuit
protection. Co-packaged integration of the silicon
driver and protection circuitry with the GaN HEMT
allows for fast protection and turn-off within 100 ns,
as shown in Figure 7.

Figure 6(b): Surge waveforms for the LMG3410R70 device
showing switching (light blue curve) operation during the V “At TI, we take all aspects of GaN reliability seriously,”
(dark blue) surging to 720 V (Source: Texas Instruments) IN said Sandeep Bahl, Distinguished Member of Technical
Staff at TI. “TI has leveraged its many decades of
silicon technology development, while recognizing the
TI has described in a technical paper the surge new opportunities that GaN brings, to think differently
robustness of the LMG3410R070 part. GaN’s superior on how to deliver a robust and reliable power solution.
transient overvoltage capability enables it to switch TI GaN devices are reliable at both the component
through surge events without avalanching. A transient level and in real-world applications. They have passed
surge voltage rating (V DS(SURGE) ) is specified, which is both silicon qualification standards and GaN industry
the peak bus voltage that the device can withstand guidelines. In particular, TI GaN products pass JEP-180,
during active operation. In this example, V DS(SURGE) is demonstrating that they are reliable for power supply
specified at 720 V, based on system considerations usage.”
Figure 5: DHTOL test circuit and data for LMG341xx parts (Source: Texas Instruments) and customer feedback, much above the operation
voltage maximum specification of 600 V.

from relevant stress conditions: using SURGE ROBUSTNESS AND
switching-accelerated lifetime testing (SALT). SHORT-CIRCUIT PROTECTION
Accelerated hard-switching stress is conducted, A voltage or current surge in a
with a 2D switching locus derived for both voltage power-line–connected application can be rare, but
and current acceleration. Data from these tests can the requirement to withstand these is essential for
then be used to build a switching stress model. This power supplies. The IEC 61000-4-5 specifications
model can then be used to predict the mean time to provide specific surge test specifications. Unlike
failure (MTTF) under customer-specific conditions. silicon devices, GaN HEMT devices do not avalanche.
Due to the limited headroom of silicon power devices
DHTOL TESTING between their rated and breakdown voltages, the
A key part of JEP-180 is the guideline to avalanche robustness is considered a metric for
demonstrate that a GaN device is reliable under the surge capability.
stringent operating conditions in a power supply.
Some of the power supply stresses are shown in
Figure 4 and include conditions like third-quadrant
operation and Miller capacitance–caused transient
shoot-through events.

The TI dynamic high-temperature operating-
lifetime (DHTOL) reliability test is based on an
H-bridge circuit, as it allows power to be recycled
during operation. Both hard- and soft-switching
stresses are applied to the devices at high power and
temperature. Conversion efficiency is monitored over
a 1,000-hour stress period. Data from the LMG34xx
parts, shown in Figure 4, at 480 V and 125°C show
efficiency within 0.1%. Figure 6(a): V and V datasheet specifications for
DS(TR)
DS(SURGE)
TI’s GaN devices (Source: Texas Instruments) Figure 7: Short-circuit protection with the LMG341x parts showing a fast turn-off response (Source: Texas Instruments)
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