ST STDES-50W2CWBC Specification sheet

Introduction
The STDES-50W2CWBC dual-coil reference design is based on the STWBC2-HP Qi-compliant, inductive wireless charger
transmitter. It supports two coils, which could work alternatively to increase the Rx positioning freedom. The solution supports
Qi EPP-compliant mode up to 15 W, featuring an ST proprietary protocol. It can also support 50 W or an even higher wireless
power transfer.
The embedded STWBC2-HP integrates the following main components:
• three pairs of half-bridge gate drivers
• a dedicated DC-DC controller that supports buck, boost, and buck-boost topologies
• high-performance Q-factor detection hardware
• a high-resolution main PWM controller
• a dedicated Qi communication modulator and demodulator
• a USB-PD controller
• a buck DC-DC
• a charge-pump
The STDES-50W2CWBC is a fully assembled reference design developed for performance evaluation only, not available for
sale.
To achieve the best performance, carry out some procedures before finalizing the application.
This document summarizes the following fundamental steps:
• power supply test
• firmware downloading test
• power-on LED status check
• parameter setting test
• presence detection test
• power transfer switching test
• ST super charger (STSC) protocol test
• ASK demodulation test
• Q-factor accuracy test
STDES-50W2CWBC test report
TN1399
Technical note
TN1399 - Rev 1 - March 2022
For further information contact your local STMicroelectronics sales office.
www.st.com

1Overview
Wireless power transfer is a fast-growing technology in many application fields. The wireless power can be from
several mW (for example, in the medical field) to tens of kW (for example, an electronic vehicle).
There are multiple physical mechanisms to address the wireless power, such as magnetic inductance, magnetic
resonance, capacitive coupling, radio frequency, laser charging, etc.
The most popular mechanism is the magnetic inductive that follows the Qi standard defined by the Wireless
Power Consortium (WPC).
The STDES-50W2CWBC dual-coil reference design follows the WPC MP-A2 topology.
Figure 1. STDES-50W2CWBC reference design
Fully assembled board developed for
performance evaluation only,
not available for sale
Figure 2. Block diagram of a typical power transfer system
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Overview
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2Specifications
The STDES-50W2CWBC specifications can be summarized as follows (refer to the figure below for the related
blocks):
• the boost DC-DC supports 60 W (20 V/3 A) input and 30 V+ output
• the full bridge converter supports an AC voltage ≤ ±100 V
• the coil switcher alternatively switches the two LC tanks for coils alternatively into high voltage
• the STLINK-V3MINI interface with SWD for firmware debug and UART for demo GUI
• the I²C interface supports external daughter boards through I²C (for example, STSAFE-A110 for
authentication)
Figure 3. STDES-50W2CWBC main blocks
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Specifications
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3Test setup
3.1 Test conditions and equipment
The following tables list the equipment and tools used to test the STDES-50W2CWBC.
Table 1. Test equipment
Item Type Features/Description Reference
I1 STDES-50W2CWBC Evaluation board x1
I2 34401A 6 ½ digit multimeter by Agilent x1
I3 6403E PC oscilloscope by Pico x1
I4 E4980A LCR meter by Keysight x1
Table 2. Test tools
Item Type Description Order code/Reference Provided by
ST
C1 STLINK-V3MINI STLINK-V3 compact in-circuit debugger and
programmer for STM32 STLINK-V3MINI Yes
C2 STM32Cube STM32 programmer tool used to download
the firmware into the evaluation board STM32Cube Yes
C3 STWBC2 GUI Tool to check the board behavior, perform
the tuning, and collect logs in case of failure - Yes
C4 Firmware Firmware binary stdes-50w2cwbc_FW_v1.0.0.0.hex Yes
C5 STWLC88 or
STWLC98
Qi-compliant inductive wireless charger
power receiver for 50 W applications or 70
W applications
STWLC88 or STWLC98 Yes
C6 Wall adapter USB PD wall adapter - No
C7 USB Type-C™ cable 4 A or 5 A cable - No
3.2 Procedure
To achieve the best performance, follow the procedure below.
Step 1. Test the power supply.
The on-board DC-DC buck converter provides a supply voltage VDD starting from an external VIN DC
source. The VDD voltage is available on an external pin. It supplies the internal voltage regulators LDO
3V3 and LDO 1V8. These regulator outputs are available on an external pin. The STWBC2-HP should
generate its own power supplies directly from the VIN.
The aim of this test is to ensure that the STWBC2-HP is correctly powered. The table below shows the
reference range.
Table 3. Internal voltage range
Item Min. (V) Typ. (V) Max. (V)
VBUCK 3.42 3.6 3.78
LDO 3V3 3.1 3.3 3.5
LDO 1V8 1.7 1.8 1.9
Step 2. Download the firmware.
The firmware offers all the standard functionalities. It also supports the STWBC2-HP embedded USB-
PD.
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Test setup
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Step 3. Check the status of the power-on LEDs to ensure that the STWBC2-HP is correctly working.
There are three LEDs on the board that indicate the STWBC2-HP power-on status when the firmware
is available.
The table below shows the correct LED status.
Table 4. Power-on LED status
Item Color Behavior
D209 Green Always on
D202 Red Long blink once plus short blink once
D203 Green Long blink once
Step 4. Set the STWBC2-HP parameters for the board initialization.
Important: Disable the FOD and protection features in the STWBC2_GUI.
Step 5. Test the presence detection alternatively on the two coils.
The table below shows the level, duration, and cycle of the presence detection.
Table 5. Presence detection specifications
Item Level (V) Duration (ms) Cycle (ms)
RING_NODE1 ~6 ~80 ~1900
RING_NODE2 ~6 ~80 ~1900
Step 6. Test the power transfer switching.
The oscillation waveform appears in the activated RING_NODE, while the switching waveform appears
in another inactive RING_NODE. The switching waveform should be off in the half bridge mode and
square-waved in the full bridge mode.
Step 7. Test the ST super charger (STSC) protocol.
The STSC can support a higher power transfer than the Qi EPP. The table below shows its basic
behavior.
Table 6. Level of the STSC power supplies
Mode VIN VDCDC
Presence detection 5 V 12 V
Digital ping 9 V 12 V
STSC 5 V 9 V 12 V
STSC 9 V 9 V 9 V
STSC 12 V 12 V 12 V
STSC 15 V 15 V 15 V
STSC 18 V 15 V 16.5~18 V
STSC 20 V 20 V 20 V
Step 8. Test the ASK demodulation.
The firmware can route the demodulation result (V, I) to a GPIO, which should be close to the Rx
modulation waveform.
Step 9. Test the Q-factor accuracy.
Comparing the Q-factor measurement accuracy with the LCR meter, the Q-factor measurement
accuracy should be close to the LCR meter.
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Procedure
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4Measurements/waveforms/test data
4.1 STWBC2-HP startup waveform
Once the board is supplied, you can check each voltage during the startup as described below:
1. the board is supplied by the USB PD adapter and the voltage is ready and stable at about 5 V
2. the internal DC-DC buck converter and LDOs are starting
3. the internal 1.8 V LDO is ready and the output is stable at 1.8 V
4. the internal 3.3V LDO is ready and the output is stable at 3.3 V
5. the internal DC-DC buck converter is ready and the output is stable at 3.6 V
Figure 4. Typical startup waveform: power-on sequence
4.2 Presence detection waveform
Once the STWBC2-HP power-up is ready, you can check the presence detection waveform at RING_NODE1
triggered by TANK1_SEL and RING_NODE2 triggered by TANK2_SEL as described below:
1. the RING_NODE1 starts oscillating about 75 ms in the end of TANK1_SEL active high and the
RING_NODE2 is off
2. the RING_NODE2 starts oscillating about 75ms in the end of TANK2_SEL active high and the
RING_NODE1 is off
3. the RING_NODE1 starts oscillating again in the end of TANK1_SEL active high and the RING_NODE2 is off
4. the RING_NODE1 and RING_NODE2 repeat the above process in a period of about 900 ms
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Measurements/waveforms/test data
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Figure 5. Presence detection waveform
4.3 Power transfer switching waveform
Once the STWBC2-HP presence detection is working correctly, you can check the power transfer switching
waveform at RING_NODE1 reference to TANK1_SEL and RING_NODE2 reference to TANK2_SEL as described
below.
1. Put the Rx coil on the Tx coil 1 and set the Rx output to 5 V. The RING_NODE1 appears sine-waved while
the RING_NODE2 is off (see Figure 6).
2. Put the Rx coil on Tx coil 2 and set the Rx output to 5 V. The RING_NODE2 appears sine-waved while the
RING_NODE1 is off (see Figure 7).
3. Put the Rx coil on the Tx coil 1 and set the Rx output to 9 V. The RING_NODE1 appears sine plus
square-waved while the RING_NODE2 is square-waved (see Figure 8).
4. Put the Rx coil on the Tx coil 2 and set the Rx output to 5 V. The RING_NODE2 appears sine plus
square-waved while the RING_NODE1 is square-waved (see Figure 9).
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Power transfer switching waveform
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Figure 6. Coil 1 in half-bridge mode
Figure 7. Coil 2 in half-bridge mode
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Power transfer switching waveform
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Figure 8. Coil 1 in full-bridge mode
Figure 9. Coil 2 in full-bridge mode
4.4 STSC waveform
The STSC protocol supports a higher power transfer. The figure below shows the typical waveform.
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STSC waveform
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Figure 10. Power automatic boost (5-20 V)
4.5 ASK demodulation waveform
The firmware can route the demodulation result (V, I) to a GPIO, which should be close to the Rx modulation
waveform. The figure below shows the typical waveform.
Figure 11. ASK demodulation frame
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ASK demodulation waveform
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