Japanese electronics company Rohm has developed a wireless power supply IC chipset compatible with near field communication (NFC) technology for compact wearables such as smart rings and smart bands.

The smart ring market has seen rapid growth in recent years. However, for extremely small ring-shaped devices worn on the finger, wired charging is impractical, while the conventional Qi wireless charging standard is difficult to implement due to constraints such as coil size.

In response, NFC-based charging, which operates at the high-frequency 13.56MHz band that enables antenna miniaturisation, is attracting increased attention, with adoption accelerating in wearables.

Consisting of a receiver (ML7670) and transmitter (ML7671), the chipset has a maximum power transfer specified at 250mW, while peripheral components such as the switching mosfets required to supply power to the charging IC are built in. The result is optimised for both mounting area and power transfer efficiency in the power class demanded by compact wearable devices.

The ML7670 power receiver IC achieves a maximum power transfer efficiency of 45% in the 250mW low output range in a form factor of 2.28 by 2.56 by 0.48mm. All firmware required for wireless power delivery is embedded directly within the IC, eliminating the need for a host MCU.

Compliance with NFC Forum (WLC 2.0) enables power transfer while maintaining compatibility with existing devices, positioning the chipset as a core element in the expanding NFC wireless power ecosystem.

The chipset is already in mass production. It has been adopted in the Soxai (pronounced sok-sai) Ring 2 launched late last year. Soxai is the Japanese developer and distributor of the original sleep-monitoring ring Soxai Ring (soxai.co.jp).

Application examples for the chipset include smart rings, smart bands, smart pens, wireless earphones and other compact devices such as wearables.

For more information, go to www.rohm.com.