Controller Supports Qi Extended Power for Faster Wireless Charging

STMicroelectronics is powering up wireless charging for mobile devices by introducing the STWBC-EP, one of the world's first chips to support the new Qi Extended Power specification. Qi Extended Power raises the maximum charging power from 5W to 15W.

The STWBC-EP combines best-in-class energy efficiency, consuming just 16mW in standby and able to wirelessly transfer more than 80% of the total input power, with unique features created by ST to enhance the user experience. These include a patented solution enhancing active presence detection to wake the system quickly when a compatible object is presented for charging.

The patented technology also enhances the performance of Foreign Object Detection (FOD), to cut power and prevent overheating if objects containing metals are brought too close to the charger. Other unique innovations enhance power control and energy transfer to maximize efficiency and ease of use.

"ST's Advanced Wireless-Charging chip enables manufacturers to create new, high-power products that offer superior features and efficiency," said Domenico Arrigo, General Manager, Industrial and Power Conversion Division, STMicroelectronics. "The Qi Extended Power support dramatically shortens charging time and our patented detection and safety innovations greatly improve safety and ease of use."

The STWBC-EP firmware is specifically designed to take advantage of the hardware to monitor and control the correct wireless charging operations. (click on image to enlarge)

The STWBC-EP provides the level of integration allowing simplification of charger designs while providing the flexibility to work with supply voltages ranging from 5V USB power up to 12Vdc.

To help accelerate time to market for product developers, ST has created an associated reference design with a Qi 15W ready-built transmitter board and documentation to get started. ST also has a 15W receiver chip (STWLC33) for use in high-speed chargeable devices, which developers can use to complete their applications.

The STWBC-EP is capable of bidirectional communication with the RX as specified by the WPC 1.2 protocol. A summary of key features include:

  • Digital controller for wireless battery charger transmitter
  • 15 W single coil inductive transmitters optimized for:
    • Cell phones and smartphones
    • Tablets and phablets
    • Charging accessories
  • Support for Wireless Power Consortium (WPC) 1.2 EPP 15 W certified applications
    • Backward compatible with 5 W WPC 1.1 applications
  • Support for half bridge topology with DC/DC
  • VIN range: 3 V to 5.5 V
    • Supports USB Vin
  • Active presence detector
  • Foreign object detection
  • Q-factor measurement
  • Parametric customization via GUI
  • Turnkey firmware solution
  • Peripherals
    • 10-bit ADC
    • UART interface
    • I2 C master fast/slow speed rate
    • GPIOs
  • Memory
    • Flash and EEPROM with read-while-write (RWW) and Error Correction Code (ECC)
    • Program memory: 32-Kbyte Flash; data retention: 20 years at 55 °C after 1000 cycles at 55 °C
    • Data memory: 1 Kbyte true data EEPROM; data retention: 20 years at 55 °C after 1000 cycles at 85 °C
    • RAM: 6 Kbytes
  • Transmitter reference design:
    • WPC Qi 1.2.3 certified
    • MP-A10 single coil 15 W topology
    • Evaluation board order code: STEVAL-ISB044V1
    • 2-layer PCBs
    • Active object detection
    • Graphical User Interface for application monitoring
  • Operating temperature: -40 °C up to 105 °C
  • Package: VFQFPN32 – 5 x 5mm

The STWBC-EP is available now and is priced from $3.175 for 1000 pieces.

Technical Notes:

The STWBC-EP contains a step-up (boost) dc-dc converter and a controller, with the Qi charging algorithms already implemented in firmware to save any need to integrate software and an additional microcontroller in their designs. Together, the converter and controller generate the input power and the control signals for an external half-bridge power stage that drives the charging transmitter antenna.

This architecture gives designers flexibility to optimize the external half bridge and its associated gate drivers for use with any supply voltage from 5V to 12V, and to ensure compatibility with USB quick chargers.


The evaluation kit, STEVAL-ISB044V1, includes a 15W Qi MP-A10 reference design, 12V 2A ac-dc adapter, a USB/UART dongle for connection to the PC and USB cable, as well as pre-loaded firmware. In addition to the supporting documentation, a graphical PC-based configuration tool is also provided to help customize settings.

STMicroelectronics NV
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