STMicroelectronics’ STWBC-WA/STWLC04 miniature chipset for wireless battery charging allows smaller, simpler and sealed sports wearables, as well as medical sensors and remote controllers.

Comprising the STWBC-WA charging-transmitter controller and STWLC04 wireless battery-charger receiver, the chipset enables power transfer up to 1W using very small coils—just an 11mm diameter coil on the receive side and a 20mm coil for the transmitter.

Power-transfer capability can be increased to 3W by using larger coils and a full-bridge circuit on the transmitter side. Further, the elimination of a conventional charging connector simplifies enclosure design and eases sealing to prevent contamination by dirt or moisture.

Able to work with Li-ion and Li-polymer battery chemistries, the chipset provides such safety mechanisms as foreign-object detection, active transmitter-presence detection and receiver thermal protection. The transmitter chip includes integrated drivers and native support for half-bridge and full-bridge topologies. The receiver supports direct battery charging and employs a 32-bit microcontroller core, buck converter with synchronous rectification, and integrated drivers.

Housed in a VFQFPN32 package, the STWBC-WA transmitter controller costs $2.70 each in lots of 1000 units. The STWLC04 receiver comes in a 77-bump, 3.12mm ×4.73mm flip-chip package and costs $1.30 in like quantities. An evaluation kit, the STEVAL-ISB038V1, is available from distributors for $112.