Another challenge is current collapse with
aluminum GaN (AlGaN) and GaN HEMT devices.
For these devices, a high bias voltage at the
drain can result in leakage current degradation,
which may be caused by carrier traps.
Moreover, the two-dimensional electron gas
(2DEG) concentration in the AlGaN or GaN
conductive channel decreases due to a change
in polarization charge generated by the surface
state/effect, resulting in current collapse. Lastly,
even a slight disturbance in the energy band
structure boundary and material structure of
ALGaN or GaN may cause 2DEG collapse.
With proper device and circuit design, engineers
can overcome these challenges and realize the
full potential of GaN devices. Meeting those
requirements, Analog Devices LTC7890/LTC7891
synchronous step-down controllers for GaN FETs
include many features that mitigate the
challenges of working with GaN FETs in power
device design. Specifically, these DC-DC
switching regulators ensure overcharging
prevention of high-side driver supplies (Figure 1)
while removing the need for catch, clamp, or
bootstrap diodes. The controllers include smart
near-zero dead times and resistor-enabled dead
times, internal optimization, and internal smart
bootstrap switches.
Figure 1: A synchronous step-down controller using GaN FETs features internal optimization and smart
near-zero dead times for high-efficiency operation at high frequencies. (Source: Analog Devices)
Challenges
However, the benefits of leveraging GaN technologies come at the cost of more complex
driver electronics. Some nuances to GaN device behavior must be accounted for to
achieve optimum performance and prevent early device failures. To achieve the higher
switching speed capability of GaN devices, designers must also employ faster and more
precise control systems and electronics.
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ADI | Powering the Future
