High-efficiency wireless charging chipset for sealed wearables

September 29, 2016 // By Graham Prophet
A miniaturized wireless battery-charging chipset from STMicroelectronics is designed to save space, simplify enclosure design and sealing, and accelerate time to market for ultra-compact sports wearables, wellness monitors, medical sensors, and remote controllers.

The combination of ST’s STWBC-WA charging-transmitter controller and STWLC04 wireless battery-charger receiver enables power transfers up to 1W with smaller coils than any other chipsets available: 11 mm diameter coils on the receive side and 20 mm for the transmitter allow tinier, slimmer form factors. Power-transfer capability can be increased to 3W by using larger coils and a full-bridge circuit on the transmitter side. Eliminating any need for a conventional charging connector simplifies enclosure design and eases sealing to prevent contamination by dirt or moisture.


The fully-featured chipset supports wireless-charging for Li-ion or Li-polymer battery chemistries and includes safety mechanisms such as Foreign-Object Detection (FOD), active transmitter-presence detection, and receiver thermal protection. The transmitter chip has integrated drivers, native support for half-bridge and full-bridge topologies, and comes with a configurable firmware option for a quick turnkey solution or customized applications. The receiver supports direct battery charging, which allows smaller circuit-board size, and features a 32-bit microcontroller core, an efficient buck converter with synchronous rectification, and integrated drivers.


There is a plug-and-play (STEVAL-ISB038V1) evaluation kit. The kit includes transmitter and receiver boards, as well as a Graphical User interface (GUI) that enables engineers to monitor system behaviour and fine-tune parameters. User manuals, in addition to Gerber and Bill of Materials files, are included.


The STWBC-WA transmitter controller is packaged as a VFQFPN32 and priced at $2.70 (1000).

The STWLC04 receiver is $1.30, in a 77-bump 3.12 x 4.73 mm flip-chip package. The STEVAL-ISB038V1 evaluation kit can be purchased from distributors for $112.


ST; www.st.com/wbc