Rohm shrinks NFC charging for wearables
Rohm’s ML7670/ML7671 wireless charging chipset provides NFC charging for compact wearables such as smart rings and fitness trackers. Operating in the 13.56-MHz band, NFC charging enables antenna miniaturization for ultra-compact devices. Following the 1-W ML7660/ML7661 chipset, the ML7670/ML7671 is optimized for even smaller wearable designs.
The chipset comprises the ML7670 receiver and ML7671 transmitter and supports wireless power transfer up to 250 mW. Peripheral components, including switching MOSFETs used to power the charging IC, are integrated. ROHM states that the 2.28×2.56×0.48-mm receiver IC reaches 45% power-transfer efficiency at 250 mW output, where it is optimized for compact wearable designs.
Rohm says the 45% power-transfer efficiency is enabled by tailored coil matching, rectifier circuitry, and reduced switching losses. Firmware for wireless power delivery is embedded in the IC, eliminating the need for a host MCU and reducing board space.
The NFC Forum WLC 2.0-compliant chipset is in mass production and is used in the Soxai Ring 2.
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