“ST has released the MASTERGAN1, the market’s first and only integrated 600 V gate driver and two enhanced Gallium Nitride (GaN) transistors in a single package. Competitors only offer one GaN transistor, while ST decided to add one more GaN, enabling a half-bridge configuration and allowing the MASTERGAN1 to be used in new topologies. Engineers can use it for LLC resonant converters when designing AC-DC conversion systems. The new devices will also be suitable for other common high-efficiency and high-end topologies, such as active-clamp flyback or forward converters, and address the design issues of higher power ratings and totem-pole PFCs.
ST has released the MASTERGAN1, the market’s first and only integrated 600 V gate driver and two enhanced Gallium Nitride (GaN) transistors in a single package. Competitors only offer one GaN transistor, while ST decided to add one more GaN, enabling a half-bridge configuration and allowing the MASTERGAN1 to be used in new topologies. Engineers can use it for LLC resonant converters when designing AC-DC conversion systems. The new devices will also be suitable for other common high-efficiency and high-end topologies, such as active-clamp flyback or forward converters, and address the design issues of higher power ratings and totem-pole PFCs.
The new device is highly symbolic because it makes it easier to popularize GaN transistors in mass-market products. Power supplies for telecommunications equipment or data centers were among the first industrial applications to use these power devices. Now with MASTERGAN1, engineers can design more energy efficient super fast chargers for mobile phones, USB-PD adapters and other power products.
Why use GaN in mobile phone power supplies?
A phenomenon that many consumers are unaware of, the power output of chargers for smartphones, tablets or laptops has grown exponentially in recent years. Manufacturers face a problem. The battery capacity remains basically the same, which is more or less related to the lack of substantial breakthroughs in material design. In the case of unable to expand the battery capacity, mobile devices can only increase the charging speed. With USB Power Delivery (USB-PD) and fast charging technology, a 50% charge in ten minutes is possible, as chargers are now capable of outputting up to 100 W in some cases. However, in order to make the overall size of the charger close to the current conventional size, the system requires a high switching frequency.
Chargers with GaN transistors are not currently available everywhere because designing such products is still a huge challenge. Take an average engineer at a mid-sized or large enterprise. He first encounters a simple cultural challenge of convincing managers and executives to design products using GaN, which is often not an easy process. Therefore, helping policymakers understand the technology is essential. After the engineer’s project proposal was approved, designing a GaN product PCB was no easy task, although developing a normal PCB is usually not difficult. In addition, it is important to deploy appropriate security protections. The great significance of MASTERGAN1 is that it can solve all these problems and make GaN technology popular in more application fields.
MASTERGAN1: Meet GaN
Electrical properties of GaN
When the market began to demand small form factor products capable of handling high power, GaN came to prominence due to its inherent properties. The GaN material itself is not new. We have been making LEDs with GaN since the 90s, and we have used GaN in blue laser heads since 2000. Today, designers can add thin layers of GaN to silicon wafers to create transistors with unique properties. The band gap of GaN is 3.39 eV, which is much higher than that of silicon (1.1 eV) and silicon carbide (2.86 eV), so the critical field strength is also much higher than the latter, which means that GaN is more energy efficient at high frequency switching .
The high band gap is the basis for these properties, and the root of the high band gap is the molecular structure of GaN. Gallium itself is a very poor conductor. However, when the nitrogen atoms disrupt the gallium lattice, the structural electron mobility increases dramatically (1,700 cm2/Vs), therefore, the electrons move at a higher rate with lower energy loss. Therefore, applications using GaN are more energy efficient when switching frequencies above 200 kHz. GaN can make systems smaller and more cost-effective.
EVALMASTERGAN: seeing is believing
Despite all this theoretical knowledge, engineers can still have a hard time convincing policymakers. While GaN transistors are nothing new, their use in mass-produced power supplies is still unique. It is much simpler to demonstrate the capabilities of GaN and MASTERGAN1 with the EVALMASTERGAN1 board. Demonstrating a physical platform will make the project plan more feasible, and can see what a single package looks like in a power supply, and even have the flexibility to modify the board according to your needs, adding a low-side voltage divider resistor or an external automatic Lift the diode to bring it closer to the final design. It also becomes easier to demonstrate support for various supply voltages. In addition, all pins of MASTERGAN1 are available to help developers test application designs early.
MASTERGAN1: Designing with GaN
Reduce design complexity
Going from proof of concept to custom design can be challenging. The schematic of the evaluation board is a good starting point, however, high frequency switching applications can be difficult to design for. If the traces on the PCB are too long, it will cause parasitic inductance problems. For half-bridge power converters, it is important to integrate two GaN transistors, while most competing products only offer one GaN transistor. MASTERGAN1 is unique because it is the only power solution today that integrates two GaN transistors. As a result, engineers do not have to deal with the complex driving issues associated with this type of application. Also, special GaN technology and optimized gate drivers make the system not need a negative voltage supply. MASTERGAN1 also has input pins compatible with 20 V signals. As a result, engineers can use it with a variety of existing and upcoming controllers.
Engineers must also address the important issue of size constraints. Phone chargers must remain compact in design. Therefore, the size of the MASTERGAN1 package is only 9 mm x 9 mm, which is a big advantage. In addition, new pin-compatible products are planned for the family in the coming months. As a result, it will be easier to replace the MASTERGAN family of products, and it will be simpler to develop new designs using a MASTERGAN1 based PCB. Finally, being able to design smaller PCBs faster can result in significant cost savings. As manufacturers strive to develop more economical solutions, MASTERGAN1 helps make designs more cost-effective, which is why we have already won customer orders.
Design reliability is another major challenge for engineers. An exploding charger can become a social media target. Systems with low reliability can put significant strain on customer service operations. However, deploying security features is far from simple. When using a GaN half-bridge topology, it is necessary to avoid two switches being turned on at the same time. Therefore, MASTERGAN1 integrates an interlock function and precisely matched propagation delay, as well as differential turn-on and turn-off gate currents. These functions enable precise and efficient switching operations. Finally, we designed the MASTERGAN1 gate driver for enhanced GaN FETs, improving system performance and reliability.
Under-voltage lockout (UVLO) protection optimized for GaN FETs prevents severe energy efficiency degradation and potential problems when operating at low supply voltages. Also, an integrated thermal shutdown function prevents the device from overheating. The level shifter and efficient input buffering of the gate driver bring very good robustness and noise immunity to the GaN gate driver. Finally, the shutdown pin allows the power switch to be put into idle mode via a dedicated pin of the MCU.