ROHM Co. Ltd has developed a wireless power supply IC chipset consisting of the receiver (ML7670) and transmitter (ML7671) 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 miniaturization, is attracting increased attention, with adoption accelerating in next-generation wearables.

This new chipset builds on the proven receiver (ML7660) and transmitter (ML7661). The maximum power transfer is 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 a solution optimized 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—all in a form factor of just 2.28-by-2.56-by-0.48mm. What’s more, 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 new chipset is already in mass production. Furthermore, it has been adopted in SOXAI RING 2, the latest model launched on December 10, 2025, by SOXAI Inc., the Japanese developer and distributor of the original sleep-monitoring ring SOXAI RING.

By: DocMemory
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