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GaN for fast-charge protection in a smartphone

Gallium nitride (GaN) in a smartphone? OPPO, a leading mobile device manufacturer in China, has confirmed that it is using bi-directional GaN high electron mobility transistor (HEMT) devices in its smartphone to control the battery’s charging and discharging currents. It’s the first time that GaN-based protection has been integrated into the phone itself. Previously, such circuitry had to be incorporated inside the charger.

The announcement came from Innoscience Technology, a supplier of low-cost gallium-nitride-on-silicon (GaN-on-Si) power solutions. The Zhuhai, China-based company has released a new device as part of its Bi-GaN series GaN devices used in the OPPO smartphones. INN040W0488 is a 40-V bi-directional GaN-on-silicon HEMT device available in the WLCSP package measuring 2.1 mm x 2.1 mm. Innoscience claims that a BiGaN HEMT can be used to replace back-to-back connected NMOS MOSFETs in a common-source configuration to achieve bi-directional switching of the battery’s charging and discharging currents.

Source: Innoscience Technology

Yi Sun, senior VP of product development at Innoscience, says that the application of GaN-on-silicon HEMT in smartphones marks the arrival of a new era for GaN semiconductors. While silicon MOSFETs are commonly used as power switches in smartphones, these components occupy significant space on a mobile phone’s main PCB, where every millimeter counts. Moreover, silicon MOSFETs may also result in considerable temperature rises and power loss when fast-charging.

On the other hand, bi-directional GaN HEMT devices save space and facilitate fast charging without suffering from reliability-limiting and potentially dangerous rises in temperature that can sometimes be seen in traditional silicon devices. According to Innoscience, its BiGaN HEMT can reduce on-state resistance by 50%, chip size by 70%, and temperature rise by 40%.

OPPO, on its part, has acknowledged the significant space saving as well as the reduction in the temperature rise of the phone during charging. The world’s first smartphone manufacturer using a GaN device as a direct charging load switcher has also hinted at adopting this wide bandgap technology in its future smartphone models.

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