Targeting Compact and Simple Sealed Wearable Devices

STMicroelectronics (hereinafter ST) has newly launched a miniaturized wireless battery charging chipset. The product offers advantages such as space savings, sealed packaging simplification, and shortened time-to-market, targeting ultra-compact sports wearables, health monitoring devices, medical sensors, and remote controls.

This chipset pairs ST's charging transmitter controller STWBC-WA with wireless battery charging receiver STWLC04, and can transmit power up to 1W with smaller coils compared to other currently available chipsets. With a receiver-side coil diameter of 11mm and transmitter-side diameter of just 20mm, it enables a more compact and slim form factor.

By applying a larger coil and full-bridge circuit on the transmitter side, power transfer performance can be enhanced up to 3W. Additionally, there is no need to use conventional charging connectors, which simplifies packaging and makes sealing operations to prevent contamination from dust and moisture much easier.

This fully-featured chipset supports wireless charging of lithium-ion or lithium-polymer batteries and incorporates safety mechanisms such as FOD (Foreign-Object Detection), active transmitter presence detection, and receiver thermal protection. The transmitter chip has an integrated driver and basically supports half-bridge and full-bridge topologies, with firmware options provided to quickly set up turnkey solutions or custom applications with ease. The receiver supports direct battery charging, allowing for circuit board miniaturization, and features an efficient buck converter with a 32-bit microcontroller core and synchronous rectifier, as well as an integrated driver.

With ST's plug-and-play STEVAL-ISB038V1 evaluation kit, wireless charging-related projects can be started immediately. The kit includes not only transmitter and receiver boards but also a GUI (Graphical User Interface) that allows monitoring of system operation and fine-tuning of parameters. User manuals and Gerber and BoM (Bill of Materials) files are also provided.

The transmitter controller STWBC-WA is available in VFQFPN32 package at a price of $2.70 per unit when ordering 1,000 units. The receiver STWLC04 is offered in a 77-bump 3.12 x 4.73mm flip-chip package at $1.30 per unit. The STEVAL-ISB038V1 evaluation kit can be purchased from distributors or st.com at a price of $112.