ST STEVAL-WBC86TX User manual

Introduction
The STEVAL-WBC86TX evaluation board, based on the STWBC86, is designed for wireless power transmitter applications and
allows its users to quickly start their 5 W Qi BPP wireless charging projects.
The STWBC86 wireless transmitter IC can deliver up to 15 W (coil dependent), however this reference design document is
limited to only provide sufficient information to develop a project for up to 5 W charging compatible with Qi 1.2.4 Baseline Power
Profile (BPP) power transfer by Wireless Power Consortium’s inductive wireless power technology.
The integrated circuit requires only a few external components and can work with 5-20 V input voltage.
Using an on-board USB-to-I2C bridge, the user can monitor and control the STWBC86 using the STSW-WPSTUDIO graphical
user interface (GUI).
The STEVAL-WBC86TX includes several safety mechanisms providing overtemperature (OTP), overcurrent (OCP), and
overvoltage (OVP) protections as well as foreign object detection (FOD) for reliable designs.
Figure 1. STEVAL-WBC86TX board
To get started with the STEVAL-WBC86TX, the following items are needed to use the reference design kit:
• Evaluation kit components:
– STEVAL-WBC86TX board
Getting started with the STEVAL-WBC86TX wireless power transmitter evaluation
board for up to 5 W Qi-BPP applications
UM3161
User manual
UM3161 - Rev 1 - July 2023
For further information contact your local STMicroelectronics sales office. www.st.com

• Additional hardware:
– USB adapter 5 V / 3 A or power supply
– 2 x USB Type-C® cables (one can be replaced with either 2.1 mm jack or pin cable)
– Windows PC
• Software:
–STSW-WPSTUDIO Wireless Power Studio PC GUI installation package
– I2C drivers
• Application notes:
– GUI guide: UM3164
Begin by installing both the I2C drivers and the STSW-WPSTUDIO GUI. Visit the ST website for additional information regarding
the STSW-WPSTUDIO GUI.
Connect a 5 V power supply to power the board using either the USB Type-C®, jack, or pin cable. Using a jumper, select the
chosen method of power delivery on header P1.
Using a USB Type-C® cable, connect the board to the PC (connector P4 on the board). This allows the user to communicate
with the board - program it and monitor its function.
UM3161
UM3161 - Rev 1 page 2/78

1 Reference design specifications
The target specifications of the STEVAL-WBC86TX evaluation board are as follows:
Table 1. STEVAL-WBC86TX target specifications
Parameter Description
Qi compatibility Qi 1.2.4 compatible
Tx application PCB area 40 mm x 24 mm
Tx coil specifications Inductance 6.3 uH, DCR 20 mOhm, ACR 20 mOhm @ 100 kHz, dimensions 53.3
mm x 53.3 mm x 6 mm
Qi Tx topology A11a
Input voltage (Vin) 5 V
Input current (Iin) 1.5 A
Host MCU STM32 used as a reference, the reference I2C driver can be ported to any other
MCU family
USB-to-I2C converter FT260, embedded in the evaluation board
Efficiency 77.6 % (5 W operation) with STEVAL-WLC38RX
81 % (peak efficiency) with STEVAL-WLC38RX at 3 W
Applicable charging gap between Tx
and Rx coils
(z-distance)
3 – 13 mm (5 W output) with STEVAL-WLC38RX receiver,
maximum 16 mm – stable communication without output enabled
Operational modes Transmitter only
UM3161
Reference design specifications
UM3161 - Rev 1 page 3/78

2 Overview of the board
The STEVAL-WBC86TX evaluation board is optimized for performance. The board features:
• STWBC86 wireless power transmitter chip with BPP 1.2.4 compatible firmware
• Very few external components, optimized BOM and PCB space
• On-chip high efficiency full bridge inverter
• 32-bit, 64 MHz Arm® Cortex® microcontroller with 8 KB SRAM
• 9-channel, 10-bit A/D converter
• On-chip thermal management and protections
• Foreign object detection (FOD) function
• I2C interface for communication with host system (optional)
• On-board USB-to-I2C converter
• Chip scale package (CSP), ROHS complaint
Figure 2. STEVAL-WBC86TX evaluation board features
• Series resonant capacitors (Ctank) and the transmitting coil form a resonant circuit. This circuit is in charge
of transmitting the power signal, so any components/tracks involved should be rated accordingly.
UM3161
Overview of the board
UM3161 - Rev 1 page 4/78

• CBT1 and CBT2 are bootstrapping capacitors, which ensure the proper functionality of the integrated
inverter. This should be considered during PCB design, as these nets generate noise and should therefore
be routed separately from sensitive circuits.
• ASK demodulation circuit - apart from transferring power, the power signal is also used for receiver to
transmitter communication. The communication signal is extracted from the power signal using the ASK
demodulation circuit and fed into the VS pin of STWBC86 for processing. For further details, refer to
Section 4.12.1 ASK communication.
• USB/I2C converter - provides a communication channel between a PC and STWBC86. LED D6 (red)
indicates the I2C converter is powered, D4 (yellow) indicates that STWBC86 is connected to the GUI. LED
D5 (green) indicates the I2C communication was initialized and is ready. Switch S1 resets the converter.
Please note that header P2 connects the converter’s I2C signals to the STWBC86 I2C signals. Short the
corresponding pins with a jumper to establish a connection between the two ICs.
• Power input (USB Type-C® connector/jack/pin header) - 3 separate inputs can be used to power the board,
but only one is used at a time. Therefore, it is necessary to select the input using a jumper on header P1.
• Red LED (D3) - connected to GPIO0, can be configured to signal various conditions (power ready,
communication active etc.).
2.1 Test points
The STEVAL-WBC86TX features several connectors and test points to provide easy access to key signals.
Figure 3. Connectors and test points
UM3161
Test points
UM3161 - Rev 1 page 5/78

Table 2. Connectors and test points
Connector / test point Name Description
VIN VIN Input voltage (power pins)
VINV VINV Inverter voltage pins
P2 I2C SDA, SCL, INT, and RST signals for I2C communication
P14 Digital interface I2C, GPIO, and RST signals
TP1 Ring node Ring node
TP2 VIN STWBC86 input voltage sensing
TP3 AC2 Resonant circuit terminal
TP4 AC1 Resonant circuit terminal
TP5 VINV STWBC86 inverter voltage sensing
TP6 V1V8 STWBC86’s 1.8 V LDO output
TP7 GND Ground
TP8 VS VS signal sensing
2.2 Basic operating modes
The STWBC86 is designed to work in transmitter mode only. Once the board is powered up, the device
automatically starts pinging (if enabled), which means it starts scanning its power transfer interface for a potential
power receiver. Once a suitable receiver is found, the STWBC86 initializes power transfer. After the receiver is
removed from the interface, the device returns to the pinging phase.
UM3161
Basic operating modes
UM3161 - Rev 1 page 6/78

3 Graphical user interface (GUI)
The STWBC86 (and other STMicroelectronics wireless charging devices) can be configured using
STMicroelectronics’ STCHARGE Wireless Power Studio GUI. The GUI can also be used to control, monitor, and
program the device.
For more information, please see the UM3164.
3.1 Connecting STWBC86 to PC GUI
Connect the board to a PC by plugging a USB Type-C® cable into the connector J3. Make sure the STWBC86
I2C pins are connected to the USB Type-C® connector. This can be done by shorting the appropriate signals
(SDA, SCL, INT) on header P2. Power up the board and open the GUI on your PC. Click the Connection button in
the top menu.
Up to two devices can be connected at a time - this allows the user to control both Rx and Tx at the same time).
Select WBC86 as the Tx and click the Connect button on the right side of the window.
Figure 4. GUI connection
UM3161
Graphical user interface (GUI)
UM3161 - Rev 1 page 7/78

Figure 5. GUI device connection
3.2 Patch and Configuration files
Firmware of the device can be updated using a Patch file (a binary file in .memh format). The latest version of the
Patch can be found on this [ST website]. Updating the firmware is not required but may improve performance of
the board.
The device can be configured using a Configuration file, a binary file containing settings of all registers, which can
be found in the GUI. The GUI can also be used to generate a custom Configuration file, making it easier to quickly
change configuration of the board and/or transfer the configuration to another board.
UM3161
Patch and Configuration files
UM3161 - Rev 1 page 8/78

3.3 Configuration file generation
Using the STSW-WPSTUDIO makes generating the Configuration file quite simple – the user can do so by
clicking the “Save TX” button in the TX Registers tab or the Common Registers tab, entering a configuration ID
number (used for version control) and pressing OK. The GUI then asks for a save destination. After choosing a
location, the Configuration is saved as a .memh file in the selected folder.
Figure 6. Generation of configuration file
Figure 7. Version of the configuration file
UM3161
Configuration file generation
UM3161 - Rev 1 page 9/78

Figure 8. Saving of the configuration file
3.4 Header file
The GUI can also be used to generate a Header file, a binary .h file containing both Configuration and Patch files.
The Header file makes programming the device using a host IC easier, as both Configuration and Patch can be
loaded at once by simply including the Header file in the host code.
UM3161
Header file
UM3161 - Rev 1 page 10/78