STMicroelectronics STEVAL-WLC98RX User Manual

UM3194
User manual
STEVAL-WLC98RX wireless power receiver evaluation board
Introduction
The STEVAL-WLC98RX evaluation board is based on the STWLC98 wireless power receiver. The board allows users to quickly
start their 15 W Qi EPP compatible wireless charging receiver projects or up to 50 W charging using the proprietary STSC
protocol.
The STWLC98 receiver requires only a few external components and offers high design flexibility. The board can be connected
to a PC using the STEVAL-USBI2CFT converter board, allowing the user to monitor and control the device through the STSWWPSTUDIO GUI software.
The evaluation board includes several safety mechanisms providing overtemperature (OTP), overcurrent (OCP), and
overvoltage (OVP) protections, as well as foreign object detection (FOD) for reliable operation.
Figure 1. STEVAL-WLC98RX evaluation board
UM3194 - Rev 1 - March 2024
For further information contact your local STMicroelectronics sales office.
www.st.com
UM3194
Getting started
1
Getting started
To get started with STEVAL-WLC98RX, you will need the following items to use the reference design kit:
•
Evaluation kit components:
•
–
STEVAL-WLC98RX board
–
STEVAL-USBI2CFT converter board
Additional hardware
–
•
STEVAL-WBC2TX50 for best results in a 50 W turnkey wireless charging system, or other Qi
compliant transmitter available on the market for up to 15 W applications
–
Electronic load
–
Windows PC for measurements and configurations
Software:
•
–
STSW-WPSTUDIO Wireless Power Studio PC GUI installation package
–
I²C drivers
Application notes:
–
–
–
–
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STSC FOD tuning guide
Coil selection guide
GUI guide
STSC Application note
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Reference design specifications
2
Reference design specifications
Target specifications of STEVAL-WLC98RX evaluation board are as follows:
Table 1. Target design specifications
Parameter
Qi compatibility
Qi 1.3 BPP and EPP protocol
Rx application PCB area
81 mm x 81 mm
Rx coil specifications
Inductance 8 µH, DCR 190 mΩ, ACR 225 mΩ
Dimensions 57 mm x 57 mm x 0.42 mm (LD81FP008-1H)
Output voltage (Vout, continuous
operation)
5 V Baseline Power Profile / 12 V Extended Power Profile / up to 20 V in STSC
Output current (Iout, Load)
Recommended current load range is 0-2.5 A
Host MCU
STM32 used as a reference; the reference I²C driver can be ported to any other MCU
family
USB-to-I²C converter
Separate dongle board
Efficiency
Applicable charging gap between Tx
and Rx coils
(z-distance)
UM3194 - Rev 1
Description
83.8 % for 50 W power transfer with STEVAL-WBC2TX50
85.3 % peak efficiency (31 W) with STEVAL-WBCTX50
15 mm for maximum power (50 W)
20 mm stable communication, may not reach full output voltage range.
Misalignment between Tx and Rx coils
(x-y offset from the center)
10 mm for maximum power (50W)
Transmitter mode
Supported, but not covered in this document
Ambient temperature
25°C
15 mm stable communication, may not reach full output voltage range.
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Overview of the board
3
Overview of the board
The STEVAL-WLC98RX evaluation board is optimized for performance. The board features:
•
•
•
•
•
•
STWLC98 wireless power receiver chip with BPP and EPP compliant firmware and STSC ready
Very few external components, optimized BOM and PCB space
On-chip high efficiency rectifier
Support for external NTC for thermal monitoring
On-chip thermal management and protections
Up to 50 W with ST proprietary protocol (STSC)
Figure 2. Main board elements
•
•
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Series resonant capacitors (Ctank) and the receiving coil together form a resonant circuit. This circuit is in
charge of receiving the power signal, so any components/tracks involved should be rated accordingly
Red LED (D3) indicates STWLC98 core power status (on when powered).
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Overview of the board
3.1
Test points
The STEVAL-WLC98RX features several headers and test points to provide easy access to key signals.
Figure 3. Headers and test points
Table 2. Header and test point descriptions
Connector
Name
4-pin header: for mounting external RX coil:
P1
Rx Coil
P3
VOUT
2-pin header + J5: VOUT output
P17
GROUND
2-pin header + J4: GROUND output
P2
VRECT
2-pin header: VRECT output
P11, P12, P13, P14, P15
GROUND
GROUND test pads
P7
5V LDO
2-pin header: 5V internal LDO
P19
NTC
2-pin header: Ground and NTC input
P6
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Description
Pin 1,2 + J2 AC2; Pin3,4 + J1 AC1_COIL
5-pin header: TEST points
P4
I²C
6-pin header: connection to USB-I²C convertor
P5
GPIO
GPIO
P8
1V2 LDO
2-pin header: 1V2 internal LDO
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Overview of the board
3.2
Basic operating modes
The receiver generally works in two modes: DC (also called standalone) mode and Rx mode.
DC mode is characterized by the wireless receiver being powered from a DC power supply such as external
power supply or USB. This mode is used for patch and configuration loading (described later). Before entering
this mode, the device must not be powered by the power transmitter. This means that the device must either be
kept away from the power transmitter or the power transmitter should be turned off.
Rx mode is used when the wireless receiver is powered from a wireless power transmitter. A stable and ongoing
power transfer between the transmitter and the receiver is indicated by LED (D3). Make sure that Rx is not
powered by external DC power before entering this mode.
Note:
If the patch and/or configuration files are not loaded (missing or corrupted) the STWLC98 does not initiate
communication and power transfer will not be established. The STWLC98 will operate in DC mode.
If the WLC98 is powered by DC voltage (to Vout) and then placed on a power transmitter, the STWLC98 will not
initiate communication and power transfer will not be established. The STWLC98 will continue to operate in DC
mode.
3.3
Functional check
Figure 4. STEVAL-WLC98RX (left) placed on STEVAL-WBC2TX50 (right) transmitter coil
The first sign of an ongoing power transfer is the D3 LED, as this LED indicates the internal power supply of the
device is ready. A continuously shining LED indicates a stable power supply, while a blinking or inactive LED
indicates an unstable and/or insufficient power supply.
The LED D3 is permanently OFF means there is no power transfer between the transmitter and the receiver.
Check if the power supply of the transmitter is connected and working properly. Power transfer termination may
also be caused by a large enough misalignment (from an ideal center-to-center position) between receiver and
transmitter coils. This issue is, to a certain degree, mitigated by the ARC mode feature, which improves spatial
freedom of the charging.
The LED D3 is blinking means some power is being transferred, but the amount is insufficient, or the transfer is
unstable. One of the reasons for such instability may be communication issues between the power transmitter
and the power receiver. The instability may also be caused by one of the protections (OVP, OCP, OTP) being
triggered.
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Graphical user interface (GUI)
4
Graphical user interface (GUI)
STWLC98 (and other ST wireless charging devices) can be configured using the STCHARGE Wireless Power
Studio GUI (STSW-WPSTUDIO). The GUI can also be used to control, monitor, and program the device.
For more information, please see STCHARGE Wireless Power Studio User Manual.
4.1
Connecting STWLC98 to PC GUI
To connect the board to a PC, you will need a USB to I²C converter. ST offers STEVAL-USBI2CFT converter
board for this purpose.
Step 1.
Connect the STEVAL-WLC98RX SDA, SCL, and GND signals to the corresponding pins of the
converter board and connect the converter board to your PC.
The red PWR LED on the converter board indicates the converter is powered.
Step 2.
Power the STWLC98 before connecting to the GUI. This can be done in one of the following ways:
–
–
–
Note:
Step 3.
Placing it onto a power transmitter, the device operates in Rx mode.
Switching it into DC mode by connecting a DC power supply to the STWLC98 VOUT pins. The
voltage must be higher than 3 V.
Switching it into DC mode by connecting the STWLC98 Vout signal to the VBUS pin of the
converter board.
The Rx registers are available only if the device is operating in Rx mode. The DC mode is mainly
used for updating patch and configuration file.
Click the [Connection] tab in the top menu.
Up to two devices can be connected at a time.
Figure 5. PC GUI main screen
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Graphical user interface (GUI)
Step 4.
Select [WLC98] as the Rx and click the [Connect icon] on the right side of the pop-up window.
Figure 6. Device selection and connection
4.2
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 at www.st.com. Updating the firmware is not required but may improve the performance of the
board.
The device can be configured using a binary configuration file for all the register settings available 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.
4.3
Configuration file generation
The configuration file can only be generated using STSW-WPSTUDIO.
Modifications to registers colored in RED will only take effect if a configuration file is generated and written onto
the device. Modifications of registers colored in BLACK will take effect immediately and can be saved to a
configuration file. During power-up, these registers are set to values defined in configuration file written in the
device. Registers that cannot be saved to a configuration file and lose their value on reboot are noted as such in
the description.
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Step 1.
First check that the device is operating in Rx mode.
To ensure that the latest values are shown in GUI, it is recommended to use the [Read [RX]WLC98]
button to dump values from device to the GUI. Then the required changes of the register can be made.
This is especially necessary when going from DC mode to Rx mode.
Step 2.
Make required changes to registers.
Step 3.
Click [Write [RX]WLC98] in any tab to confirm changes.
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Graphical user interface (GUI)
Step 4.
Click the [Save RX] button in the RX Registers tab or the Common registers tab.
Figure 7. Save RX button
Step 5.
Enter a Configuration ID number (used for version control) and press [OK].
Figure 8. Configuration ID field
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Graphical user interface (GUI)
Step 6.
Note:
Choose your location for the save file.
After choosing a location, the configuration will be saved as a .memh file in the selected folder.
Modifications to registers colored in RED only take effect if the config file is generated first and then
uploaded to device. Those changes will be preserved upon reboot.
Figure 9. Save folder selection
4.4
Header file
The GUI can also be used to generate a binary .h header 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
simultaneously by simply including the header file in the host code.
4.5
Header file generation
A custom header file can be generated in the [Header Generator] tab.
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Graphical user interface (GUI)
Step 1.
Start by selecting [WLC98] in the top menu.
Figure 10. Device selection
Step 2.
Continue by selecting the patch and configuration files and press [Generate].
A pop-up window will appear, asking to confirm you have selected the correct patch version.
Figure 11. Confirmation of patch version
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Graphical user interface (GUI)
Step 3.
Choose a save destination.
After choosing a location, the header file will be saved as a .h file in the selected folder.
Figure 12. Header file save
4.6
Programming the device
To program the device, the device must be switched into a so-called DC mode. Before switching to DC mode, first
make sure power transfer is not active. The simplest way to achieve this is to either remove the receiver from the
transmitter or to power down the transmitter.
To enter DC mode, connect a DC power supply to the VOUT pins. The voltage must be higher than 3 V.
The device can be programmed in the following ways:
1. By using a header file that simultaneously loads the configuration and patch files.
2. By loading the two memh files separately using the GUI.
4.6.1
Using header file
Step 1.
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In the GUI, navigate to the [Programming] tab in the side menu.
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Graphical user interface (GUI)
Step 2.
Select [WLC98] in the top menu and [HEADER] in the toggle selector.
Figure 13. Loading the header file
4.6.2
Step 3.
Select the .h file you want to write.
The GUI will automatically identify the patch and configuration files included in the header file.
Step 4.
Press the [Write] button to load the header file onto the device.
Using memh files
Step 1.
To load the memh files (patch and configuration) using the GUI, navigate to the [Programming] tab in
the side menu.
Step 2.
Select [WLC98] in the top menu and [MEMH] in the toggle selector.
Figure 14. Loading the patch and configuration files
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Step 3.
Select the patch and configuration files you want to write.
Step 4.
Press the [Write] button to load the .memh files into the device.
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Device description and operation
5
Device description and operation
5.1
System block diagram
Figure 15. STWLC98 system block diagram
5.2
Integrated power rectifier
The synchronous rectifier is a key block in charge of converting the AC power signal from the receiving coil into a
DC supply rail for the following linear regulator. The rectifier consists of four N-channel MOSFET transistors in Hbridge configuration driven by a control block that monitors the voltage at the AC1 and AC2 pins to optimize
switching. Different driving schemes for the rectifier switches are possible. The MCU core dynamically selects the
optimal one to maximize the overall efficiency as a function of the operating point.
When selecting the filtering capacitor at the output of the synchronous rectifier, keep in mind that the capacitance
value should be designed large enough to minimize the residual AC voltage ripple and to provide sufficient energy
storage to sustain load transients and prevent the transients from impacting ASK communication with the
transmitter.
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Device description and operation
5.2.1
Iload
To maintain rectifier stability and communication clarity, providing a certain minimal load to the rectifier is
recommended. The STWLC98 Iload function draws sufficient current from the rectifier when the load current is
too small.
The rectifier current consists of the load current, the Iload current, and the IC consumption current. The Iload
function automatically adjusts its current to ensure that the rectifier current is 40 mA (Iload value set by default).
The Iload function is disabled when the rectifier current exceeds 40 mA, and is enabled again when the rectifier
current drops below 40 mA.
The Iload current value is set to 40 mA as default, and the function cannot be disabled in the GUI. The Iload
current value can however be adjusted in the GUI in the RX ILOAD RESERVOIR register from 10 mA to 500 mA.
5.3
Internal ADC channel monitor
The STWLC98 allows the user to monitor key operational parameters using an internal ADC. Instantaneous
values can be displayed in the [Charts] tab of the GUI.
Up to four graphs can be displayed simultaneously. In addition to the values that can be plotted in a graph, the
STWLC98 ADC also measures other signals, as well as external ADC inputs. These values can be found in the
GUI under [Common Registers]>[Mode Monitor].
Figure 16. PC GUI charts
5.3.1
NTC
This external ADC input is used to monitor temperature with help of an external temperature sensor (NTC). This
value is stored in register labeled NTC TEMP. The GUI is always converting and displaying the value of this
register in mV. If external host MCU is used, it can read the value of this register and convert to volts using the
following formula:
NTC_Voltage V =
RegisterValue
∙ 0.9
210 ∙ 16
Note:
The maximum voltage applied to this input must not exceed 1.2 V and ADC range is 0 - 0.9 V. NTC
overtemperature protections monitor this input; see the relevant section.
5.3.2
ADCIN
This external ADC can be used for any purpose the application may require. Take note that the maximum voltage
applied to this input must not exceed 1.2 V and the ADC range is 0 - 0.9 V. This input is scanned periodically and
the value is stored in the ADC IN register. There is no action/protection tied to this register.
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Device description and operation
The GUI always converts and displays the value of this register in mV. If external host MCU is used, it can read
the value of this register and convert to volts using the following formula:
ADCIN_Voltage V =
5.4
Main LDO regulator
RegisterValue
∙ 0.9
210 ∙ 16
The main LDO regulates the rectified voltage to a target value specified by the user. The output voltage is
configurable in the 0.5–20 V range in 25 mV steps. The default value of output voltage is 5 V for BPP (5 W) mode
and 12 V for EPP (15 W) mode, respectively. However, the target value can be easily changed in the GUI ([Rx
Configuration]>[RX VOUT SET register]) or by an external host controller.
5.4.1
Regulation loops and protections
The main LDO regulator is equipped with two protections:
1. Input voltage loop (IVL): when the Vrect voltage falls below a set threshold, the Vout is temporarily limited until
the Vrect rises above the threshold again. The default threshold for this protection is 3.5 V, but can be set from
3.5 V to 11 V in 0.5 V steps.
2. Input current loop (ICL) with overcurrent protection (OCP): this protection is triggered when the rectifier current
rises above a set threshold. The threshold can be adjusted from 0.1 A to 2.5 A.
Note:
For more information refer to the Protection section.
5.4.2
Dload
To guarantee the stability of the main LDO regulation loop, a dummy load (dload) is connected between output of
the main LDO and ground. It is used to ensure that output current is at least 10 mA.
5.5
UVLO
The STWLC98 is also equipped with a UVLO function. The UVLO is triggered when the digital core input voltage
(VRECT) drops below 3 V, which results in the device being powered down. Normal operation is resumed as soon
as the input voltage rises above 3 V.
Note:
This protection ensures that the digital core is powered by a sufficiently high voltage. Not to be confused with
VOUT UVLO, which will be described later.
5.6
Chip enable
The device can be disabled (forced into reset) by pulling the RSTB signal to the ground. When the RSTB signal is
released and left to be pulled up, the device resumes normal operation. During reset, AC1 and AC2 signals are
connected to ground (coil is shorted) to protect the device.
Placing a power receiver with a shorted coil on the power transmitter will cause high current spikes in the
transmitter coil. An alternative way to ensure that power transfer does not start is to use the GPIO function called
GPIO_FUNC_RX_DIS_COM. This function disables ASK communication of STWLC98, so there will be no
response to the digital ping and power transfer will not start.
5.7
Power up sequence
When the device is placed onto a power transmitter and the patch and configuration files are loaded into the
device, the device initiates communication with the transmitter and power transfer commences once all the steps
required by the Qi specification (see Section 5.10: WPC Qi wireless power transfer) are completed.
If the patch and/or configuration files are not loaded, the device does not initiate communication or power transfer.
See Section 4.6: Programming the device for device programming instructions. Communication is also not
initiated if one or both of the patch or configuration files are corrupted.
During the initial phase of power transfer, STWLC98 operates in proprietary ARC mode, which renders the powerup sequence smoother and more reliable (see Section 5.14: Adaptive rectifier configuration (ARC) mode ).
Once VRECT rises to a sufficient voltage, the internal power management system starts operating. The digital
core is powered up and ready to control the internal circuitry. Default device settings are used until the digital core
is woken and the firmware loads the settings from the configuration file, at which time the device is then ready to
operate.
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Device description and operation
5.7.1
Vout soft start
Once power transfer is established and VRECT reaches the required voltage, Vout can be enabled to effectively
connect the load. To eliminate high current spikes during load connection, Vout soft start can be enabled. The
time duration of the Vout soft start functionality is specified in RX VOUT SOFT START DELAY register. There are
two different limitation during soft-start:
1. The RX SOFT START IIN will efffectively limit the load current to the value specified in RX SOFT START
IIN SEL register by lowering output voltage.
2. RX SOFT START VIN will lower the output voltage if the Vrect voltage falls below the threshold specified in
RX SOFTSTART VIN SEL.
Figure 17. Vout soft start configuration
5.8
LDOs
The device is equipped with a 5 V, a 1.8 V, and a 1.2 V linear regulator (LDO), with the 1.8 V and 1.2 V LDOs
deriving their power from the former.
The 1.2 V LDO powers the digital part of the IC, while the 5 V LDO powers the analog part of the IC but can also
be used to power external low-power circuitry (such as LEDs). The maximum current externally drawn from this
LDO should not exceed 20 mA.
External LDO capacitors should be placed as close to the IC as possible.
The STWLC98 is most often used in high power applications with an output voltage close to 20 V. Deriving the
5 V necessary for the internal circuitry may cause temperature rise in the device because of the power dissipated
on the internal LDO. To prevent this, an external 5 V source can be used to supply internal 5 V power rail. Please
refer to the relevant guidelines in this document.
5.9
Protections overview
STEVAL-WLC98RX board uses both hardware and software protections to ensure safe operation of both the
device and the board. The purpose of those protections is to avoid damage caused by sudden overvoltage or
overcurrent operating conditions. Temperature is also monitored; the device is equipped with an internal
temperature sensor and pins for external NTC connection.
Protections can be configured in the GUI and changes applied in the generated .memh configuration file. Each
protection can also be configured to disable device output and force the receiver to send an EPT packet when
triggered. If a transmitter receives this packet, it terminates power transfer immediately.
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Device description and operation
As mentioned above, the protections are divided into hardware operated protections and firmware controlled
protections. Hardware protections are generally much faster but have limited threshold settings in terms of step
size. Firmware protections instead use ADC sampled data and offer finer threshold settings but slower trigger
times. According to best practice, the lower threshold is usually set for firmware protection, which should first raise
interrupts to inform the host MCU, while hardware protection will intervene with more forceful actions (for
example, grounding AC1/AC2) if the situation continues to deteriorate.
All the protections are listed and described below, followed by a detailed description of each protection.
Overvoltage protections (OVP)
•
Ping overvoltage protection (POVP):
–
•
Protects the device against excessive rectifier voltages (VRECT) during the ping phase (first few
milliseconds after the power-up and before the device is started with OVPH properly activated).
–
The threshold is set to 14 V and is released as soon as the rectifier voltage drops below 11 V.
–
It is disabled after the digital part of the device is powered up (the internal 2.5 V LDO reaches the
target value).
–
When triggered, the AC1 and AC2 pins of the device are shorted to ground
–
It cannot be disabled, and the threshold cannot be adjusted
Two stage soft overvoltage protection (OVPS):
–
•
Connects external resistors between the VRECT node and ground. This causes the VRECT voltage
to drop, without dropping low enough to lose communication with the transmitter.
–
It can be disabled in the GUI
–
It can be configured to disable VOUT when triggered
–
It can also be configured to force the receiver to send an EPT packet when triggered
–
The threshold of this protection is programmable from 22.5 to 25 V; the protection is released when
Vrect drops by the hysteresis value
Hard overvoltage protection (OVPH):
–
–
–
–
•
It shorts AC1 and AC2 pins to ground when triggered
It can be disabled in the GUI
This protection can be configured to disable VOUT when triggered
The threshold of this protection can be set from 25 to 26.5 V with a 0.5 V step. The protection is
released when Vrect drops to the release value.
Firmware overvoltage protection (ADC OVP):
•
–
This protection monitors the VRECT voltage, based on AD converter sampling
–
This protection can be configured to disable VOUT when triggered
–
The protection can also be configured to force the receiver to send an EPT packet when triggered
–
The threshold of this protection can be set in range of 0 to 26 V
Vout overvoltage protection (VOUT OVP):
–
–
–
This protection monitors the output voltage and has fixed threshold of 21 V
It can be configured to disable VOUT when triggered
It can also be configured to force the receiver to send an EPT packet when triggered
Undervoltage protections (UVLO)
•
Input voltage loop (IVL):
•
–
Monitors the rectifier voltage and limits VOUT when VRECT drops below a set threshold.
–
The threshold can be set from 3.5 to 11 V in 0.5 V increments. The default value is 4 V.
Output undervoltage protection (VOUT UVLO):
–
–
–
–
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Monitors the rectifier voltage and sets an interrupt bit when VRECT drops below a set threshold.
Can be configured to disable the output when VRECT drops below a set threshold.
Can also be configured to force the receiver to send an EPT packet
The threshold can be set from 3.5 to 11 V in 0.5 V increments
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Device description and operation
Overcurrent protections (OCP)
•
Input current loop (ICL) with over current protection (OCP):
–
–
•
–
Monitors the output current
If OCP is disabled: after output current reaches ICL threshold, main LDO will lower output voltage to
maintain output current below ICL threshold
If OCP is enabled: after reaching ICL threshold, OCP interrupt bit is set and:
–
◦
OCP can be configured to also disable VOUT when triggered
◦
OCP can also be configured to force the receiver to send EPT packet when triggered
The threshold can be set from 0 mA to 2.5 A with 0.1 A increments
Firmware overcurrent protection (ADC OCP):
–
–
–
–
•
Monitors the output current, based on AD converter sampling
Can be configured to disable VOUT when triggered
Can also be configured to force the receiver to send an EPT packet when triggered
The threshold can be set from 0 to 3.5 A with 1 mA increments
Output short current protection (SCP):
–
–
–
Monitors if VOUT is shorted
Can be configured to disable VOUT when triggered
Can also be configured to force the receiver to send an EPT packet when triggered
Overtemperature protections (OVTP)
•
Hardware thermal shutdown (TSHUT):
•
–
Monitors internal chip temperature (close to main LDO)
–
Can be configured to disable VOUT when triggered
–
For internal temperature threshold, can be set from 105 to 135°C with 10°C increments
Firmware overtemperature protection (ADC OVTP):
•
–
Sense internal chip temperature (close to main LDO), based on AD converter sampling
–
Can be configured to disable VOUT when triggered
–
Can also be configured to force the receiver to send an EPT packet when triggered
–
The threshold can be set from 0 to 200°C with 0.1°C increments.
NTC OVTP
–
–
–
–
–
5.9.1
Senses NTC voltage, usually used for coil temperature monitoring
Can be configured to disable VOUT when triggered
Can also be configured to force the receiver to send an EPT packet when triggered
For hardware protection, threshold can be set at 250, 300, 350, or 400 mV.
For firmware protection, threshold can be set from 0 to 900 mV with 1 mV increments.
Two-stage soft overvoltage protection (OVPS)
OVPS protects the device against excessive rectifier voltage. When VRECT rises above a set threshold, the
device tries to lower its value by connecting external power resistors (labeled IEXT) from VRECT to ground
through internal transistors. This approach should lower the rectifier voltage without losing communication with
the transmitter. Therefore, triggering this protection does not necessarily lead to regulation failure or power
transfer termination. The protection can also be configured to disable the output and/or force the receiver an to
send EPT packet when triggered.
This protection has two stages (OVPS1 and OVPS2). For each stage, the thresholds can be set separately
(OVPS1 must have a lower threshold than OVPS2):
•
•
OVPS1 thresholds: 22.5, 23.0, 23.5, 24.0 V
OVPS2 thresholds: 23.5, 24.0, 24.5, 25.0 V
Both stages are released after VRECT falls below “OVPS1 threshold - 1 V"
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Device description and operation
Figure 18. Two-stage OVPS Rx protection threshold setting
Figure 19. Two-stage OVPS Rx protection settings
5.9.2
Hard overvoltage protection (OVPH)
OVPH is the fastest (hardware) overvoltage protection and prevents the rectifier voltage from rising above a safe
level. Triggering the protection causes STWLC98 to short AC1 and AC2 to ground, effectively shorting the
receiving coil. This protection should be used as the last resort, as shorting the receiving coil will cause the
transmitter current to rise dramatically. The HOVP threshold should be set higher than all other STWLC98
overvoltage protection thresholds (but still lower than AMR listed in the datasheet).
The threshold value can be: 25.0, 25.5, 26.0, 26.5 V. It is set in RX THRES OVPH register.
Release value can be 10.0, 13.0, 16.0, 19.0 V. It is set in the RX RELEASE OVPH register.
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Device description and operation
Figure 20. HOVP Rx protection threshold setting
Figure 21. HOVP Rx protection settings
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Device description and operation
Figure 22. Hard overvoltage protection
Typical voltage waveforms of AC1, AC2 (rectifier input) signals and Vrect (rectifier output) signal during protection engaged:
cursors show Vrect voltage levels for protection engagement and disengagement.
5.9.3
Firmware overvoltage protection (ADC OVP)
Firmware OVP is the slowest overvoltage protection, so its threshold should be the lowest among the available
overvoltage protections. It monitors the rectifier voltage (Vrect) and can be configured to disable device output
and/or force the receiver to send an EPT packet when triggered. The threshold range is 0 to 26 V.
Figure 23. Firmware OVP Rx threshold setting
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Device description and operation
Figure 24. Firmware OVP Rx settings
5.9.4
Output overvoltage protection (VOUT OVP)
Firmware VOUT overvoltage protection monitors VOUT against a fixed 21 V threshold that cannnot be changed.
This protection can be configured to disable VOUT and/or send an EPT when triggered.
Figure 25. Firmware VOUT OVP Rx threshold setting
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Device description and operation
5.9.5
Overcurrent protections (OCP)
The STWLC98 IC is equipped with two separate overcurrent protections, one operated by hardware and one
managed by the firmware.
The hardware OCP can generate interrupts, disable STWLC98 output, and/or send an EPT. The threshold can be
set from 0 to 2.5 A in 100 mA increments. This hardware protection is tied to ICL (input current loop) functionality
and shares the same threshold. This protection first requires ICL enabled, before the OCP and appropriate
functions (EPT/VOUT off) are enabled.
Table 3. Description of OCP protection behavior for combinations of all related setting registers
ENABLE: logic 1 in given register
DISABLE: logic 0 in given register
X: does not matter
Note:
Rx ICL EN
RX OCP EN
PROT
RX OCP
VOUT OFF
RX OCP EPT
ENABLE
DISABLE
X
X
ENABLE
ENABLE
DISABLE
DISABLE
Main LDO lowers output voltage to maintain output current
below threshold. OCP can then trigger interrupt (depending on
interrupt settings)
ENABLE
ENABLE
ENABLE
DISABLE
OCP turns off VOUT. Can also trigger interrupt (depending on
interrupt settings).
ENABLE
ENABLE
DISABLE
ENABLE
Main LDO lowers output voltage to maintain output current
below the threshold and OCP sends EPT. Can also trigger
interrupt (depending on interrupt settings).
ENABLE
ENABLE
ENABLE
ENABLE
OCP sends EPT and turns off VOUT. Can trigger interrupt
(depending on interrupt settings).
DISABLE
X
X
X
Reaction on reaching threshold (RX ICL THRES)
Main LDO lowers output voltage to maintain output current
below the threshold.
Nothing happens
As the threshold of this OCP protection is shared with ICL functionality, ensure that the ICL threshold is set in
the [Rx Configuration] tab.
Figure 26. ICL Rx selection and threshold
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Device description and operation
Figure 27. OCP Rx protection settings
The firmware OCP threshold can be adjusted from 0 to 3.5 A. It can also be configured to disable device output
and/or force the receiver to send an EPT packet when triggered. This protection is independent of ICL
functionality. The ADC sample value of current used by firmware OCP is accessible to the user in [Common
Registers]>[Mode Monitor]>[ICUR].
Figure 28. Firmware OCP threshold settings
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Device description and operation
Figure 29. Firmware OCP setting
5.9.6
Overtemperature protections (OVTP)
The STWLC98 is equipped with two overtemperature protections: one operated by hardware and one managed
by the firmware.
The hardware OVTP (called TSHUT) causes the AC1 and AC2 pins to be shorted to ground when triggered. The
default threshold value is set to 105°C (released at 95°C), however the threshold can be adjusted in the GUI
(options: 105, 115, 125, 135°C).
Figure 30. TSHUT Rx protection threshold setting
Hardware OVTP can also be configured to disable the device output when triggered. Sending EPT is unavailable
because AC1 AC2 are shorted to ground after the protection is triggered, which renders ASK communication
impossible.
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Figure 31. TSHUT Rx protection setting
The firmware OVTP can be adjusted from 0 to 200°C (with a 0.1°C increment) and can be accessed in the GUI.
Figure 32. Firmware OVTP protection threshold setting
Firmware OVTP can also be configured to disable the device output and/or force the receiver to send an EPT
packet when triggered.
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Device description and operation
Figure 33. Firmware OVTP Rx protection setting
5.9.7
NTC protection
An external NTC can be used to further monitor the operational temperature of the board. The user may choose a
component or board region to be monitored by placing the NTC on or around it, although monitoring the receiving
coil is the most common practice.
Together with a pull-up resistor, the NTC forms a voltage divider, which is connected to the STWLC98 NTC pin. It
is recommended to design the voltage divider (from 1V2 voltage rail) to reach the (low) NTC threshold at the
highest allowed temperature.
Note:
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Even though the NTC pin is 1.2 V tolerant, the maximum sampled voltage by the internal ADC is 0.9 V, which
must be considered during NTC and pull-up resistor selection.
There are two NTC protections, one is operated by hardware (which is faster) and one managed by firmware.
In hardware protection, NTC voltage is compared with a selectable internal reference, which can be set to 250,
300, 350, or 400 mV. When the NTC voltage reaches the selected reference and triggers the protection, AC1 and
AC2 are shorted to ground, effectively shorting the receiving coil. This protection should be used as the last
resort, as shorting the receiving coil will cause the transmitter current to rise dramatically. This protection can be
configured to also disable device output.
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Device description and operation
Figure 34. Hardware NTC protection (NTC TSHUT) threshold settings
Figure 35. Hardware NTC protection (NTC TSHUT) settings
Firmware operated NTC protection has a threshold range from 0 to 900 mV with 1 mV increments. This threshold
is compared with voltage fed from the NTC voltage divider to the NTC pin. This protection can be configured to
only rise interrupt and/or turn off output and/or send EPT. In firmware NTC protection, the threshold value and
actual reading are presented in raw values (ADC values), which the GUI converts into millivolts.
If a different host controller is used, use following formula to calculate ADC millivolt values from the I²C register
readout:
NTCvoltage mV
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0.9 ∙ REG
value
210
=
16
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Device description and operation
Figure 36. Firmware NTC protection threshold setting
Figure 37. Firmware NTC protection setting
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Device description and operation
Figure 38. Reading current measured value on NTC pin
5.9.8
Foreign object detection (FOD)
Foreign object is any object placed either on or near the transmitting coil, which is not considered a valid wireless
power receiver and is magnetically active. Presence of the magnetic field generated by the transmitting coil may
cause eddy currents to form in the foreign object (such as coins, keys etc.), which in turn would heat the object to
potentially dangerous temperatures. To avoid possible damage to the device or even injury of the user, the power
transmitter must be able to detect presence of a foreign object. This detection can be implemented in several
different ways.
One of the most common ways is estimating the amount of power lost in the system. The power receiver indicates
the total amount of received power from the power transmitter. This power consists of power available to the load
and power loss which occurs on the supporting circuitry. Power loss on the power receiver side may occur in the
following locations:
•
•
•
•
•
The receiving coil and series resonant capacitors
The rectifier
The post-regulation stage
In tracks and cables
Other locations
A high power loss value may indicate presence of a foreign object.
The STWLC98 uses precise internal AD converters to perform voltage and current measurements and 32-bit
arithmetic to ensure sufficient accuracy. The STWLC98 then uses the measured values to create a mathematical
model to estimate the received power, which are then sent to the power transmitter for evaluation.
For more information regarding FOD please refer to the Qi specification, the guide shown later in this document,
and the FOD tuning application note.
5.10
5.10.1
WPC Qi wireless power transfer
Qi Baseline Power Profile
The flowchart in the figure below shows steps required to achieve power transfer in the Baseline Power Profile
(BPP) according to Qi 1.3.
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Device description and operation
Figure 39. Qi Baseline Power Profile flowchart
•
•
•
•
5.10.2
Selection: is the default state in which the power transmitter periodically scans its wireless power interface
for a potential power receiver. When a suitable power receiver is detected, the power transmitter proceeds
to the (digital) ping phase.
Digital ping: this phase is an interrogation session during which is the potential power receiver expected to
reply through amplitude shift-keying (ASK) modulation as defined by the Qi specification. After a valid
power receiver is detected, the transmitter proceeds to the Identification & Configuration phase.
Identification & Configuration: this phase is aiming to identify the receiver and to gather information
necessary for a stable and reliable power transfer, such as the maximum power or FSK communication
parameters. After receiving the information, the power transmitter creates a Power transfer contract,
basically a summary of the operational parameters. After the power receiver is identified and the power
transfer is created, the power transmitter proceeds to the power transfer itself.
Power transfer: this is the final step. The power transmitter initially increases and subsequently modulates
the transmitted power in response to control (feedback) data from the receiver. The receiver periodically
sends information to the power transmitter, such as required power (CEP), received power (RPP) etc.
which are used to maintain a closed control loop. If a critical event (e. g. over-voltage, over-current or overtemperature) occurs, the power transmitter shall terminate the power transfer immediately.
Qi Extended Power Profile (EPP)
Extended Power Profile (EPP) is another wireless power transfer profile described by the Qi specification and is
used to deliver up to 15 W of power. To enter EPP, both the transmitter and the receiver must comply with the Qi
EPP specification. Negotiation and calibration steps are required before entering power transfer. A renegotiation
phase might be used after initiating the power transfer. In the renegotiation phase, the power receiver may
request adjustments of the power transfer contract.
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Device description and operation
Figure 40. Qi Extended Power Profile flowchart
•
•
Note:
•
•
•
5.10.3
Negotiation: in this phase the power receiver negotiates with the power transmitter to fine tune the power
transfer contract.
Calibration: in this phase the power transmitter can improve its ability to detect foreign objects during
power transfer by receiving additional information at two different loads from the power receiver.
Changing the output voltage must respect the overall system design (selected coil, transmitter type etc.).
Output load transient response strongly depends on correct output capacitors design. Severe load
transients may lead to temporary output voltage collapse due to the overall TX-RX response time.
The initial load at power-up should not exceed 2.5 W and should be ramped up smoothly to full power
after power transfer is established.
Wireless power interface
Wireless power interface is the area in which power transfer takes place. It consists of the transmitter (primary)
power interface and the receiver (secondary) power interface. The main component of the interfaces is the
transmitting/receiving coil. The user should avoid placing any objects which are magnetically active and not
required for power transfer on or near the wireless power interface in order to avoid possible damage or injury
(see Section 5.9.8: Foreign object detection (FOD)). Detection of a valid receiver on the primary wireless power
interface is performed by analog and digital pings.
Analog ping is a short burst generated by the power transmitter. The power transmitter then evaluates if the
resonant frequency and/or resonant circuit capacitance changed, as such change might indicate presence of a
potential power receiver. However, the burst does not carry sufficient energy to wake the power receiver.
Digital ping is a more energetic burst of power generated by the transmitter; its parameters are defined by the Qi
specification. The target of this burst is to generate enough power for the receiver to establish communication
between the transmitter and the receiver.
The Qi specification defines a specific way the receiver is expected to answer the digital ping. The reason is that
only a proper answer can inform the transmitter that a valid power receiver was placed on the wireless power
interface.
5.11
Bidirectional communication
The amount of power transmitted is (from a control standpoint) fully dependent on the operating conditions of the
power transmitter (i.e., its bridge voltage, operating frequency, and duty cycle).
Since there is no direct electrical feedback from the load (system output) to the power transmitter, the power
receiver must establish communication with the power transmitter to provide this feedback instead.
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Device description and operation
To match load requirements and prevent excessive power transmission, the power receiver communicates to the
power transmitter the required power level using amplitude shift keying (ASK). This is done by the receiver
modulating the amount of power it draws from the power signal. The transmitter detects this as a modulation of
the voltage across and/or current through the transmitting coil and adjusts its operating conditions accordingly.
The power transmitter can communicate to the receiver as well, this time using frequency shift keying (FSK). This
is done by the power transmitter directly modulating the power signal. Communication in this direction enables
proprietary communication.
5.11.1
ASK communication
A state (either HI or LO) is characterized by the amplitude being constant (with a certain variation Δ) for at least
150 µs.
If the power receiver and power transmitter coils are properly aligned, then for all appropriate loads, at least one
of the following three conditions shall apply.
•
•
•
The difference of the amplitude of the transmitter coil current in the high and low state is at least 15 mA.
The difference of the amplitude of the transmitter coil voltage in the high and low state is at least 200 mV.
The difference of the transmitter coil current in the high and low state is at least 15 mA. The transmitter coil
current is measured at instants in time that correspond to one quarter of the cycle of the control signal
driving the half-bridge inverter.
Figure 41. HI and LO states in ASK communication
Table 4. HI and LO state parameters
Parameter
Symbol
Value
Unit
Maximum transition time
tT
100
µs
Minimum stable time
tS
150
µs
Current amplitude variation
Δ
8
mA
Voltage amplitude variation
Δ
110
mV
The power receiver uses a differential bi-phase encoding scheme to modulate the data bits onto the power signal.
The power signal is then demodulated by the power transmitter demodulation circuit and the demodulated signal
is processed.
The communication itself is carried out via packets. Each packet consists of 4 parts and each of those parts
consists of several bits/bytes.
Each communication bit is synchronized to the power receiver’s internal 2 kHz clock signal period. A ONE bit is
encoded as two transitions of the power signal, while a ZERO bit is encoded as a single transition.
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Figure 42. Example of a differential bi-phase encoding scheme
To transmit a single byte of data, the power receiver must send an 11-bit sequence. This sequence consists of a
START bit (ZERO), the 8 data bits of the byte (LSB first), a parity bit and a STOP bit (ONE). The parity is odd,
meaning an even number of ONE bits in the data byte results in the parity bit being equal to ONE, while an odd
number of ONE bits in the data byte results in the parity bit being equal to ZERO. An example of such message
can be seen in the picture below:
Figure 43. Example of asynchronous serial format
A packet consists of a preamble, header, message, and checksum. The preamble contains 11 to 25 ONE bits
and enables the power transmitter to synchronize with the incoming data. The header, message and checksum
are sequence of three or more bytes. The header indicates the packet type while also implicitly providing the size
of the message. The checksum consists of a single byte. It is calculated as an exclusive-OR of both the header
and message bytes and enables the power transmitter to check for transmission errors.
For a more detailed explanation please refer to the Qi Specification, Section Power Receiver to Power Transmitter
communications interface.
STWLC98 uses integrated low resistance N-channel MOSFET transistors to modulate the power signal. The
internal switches are connected to the COMA1, COMB1, COMC1, COMA2, COMB2, and COMC2 pins. As shown
below, these pins are connected to the AC1 and AC2 nodes through external capacitors, therefore connecting
those capacitors modulates the impedance seen by the coil, which is reflected onto the primary (transmitter) coil
as a change in current and/or voltage.
The figure below shows the ASK modulation capacitor connections, as well as an optional ASK demodulation
circuit that is required for transmitter mode operation. From an application point of view, the physical layer of
communication is handled by the STWLC98 firmware and the host MCU only fills data to send to relevant register.
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Device description and operation
Figure 44. ASK modulation capacitor connections
5.11.2
FSK communication
The power transmitter modulates the power signal by switching between its normal operating frequency fop and its
modulated frequency fmod. The difference between fop and fmod can be described by two parameters: polarity
and depth.
Polarity is given by the difference between fmod and fop. A positive polarity corresponds to a positive difference,
while a negative polarity corresponds to a negative difference.
Depth describes the magnitude of difference between fop and fmod.
Both polarity and depth may be changed by power the receiver via a configuration packet sent during the
establishment of a power contract. The values of polarity and depth contained in the configuration packet may be
changed in the GUI in the RX PT Contract tab.
Note:
A negative polarity results in a higher induced voltage on the power receiver coil and should therefore be used
with care.
FSK communication is executed via packets consisting of a header, a message, and a checksum. The header is a
single byte which indicates the packet type, while also implicitly providing the size of the message part. The
message size can range from 1 up to 27 bytes. The checksum is a single byte which provides a way to check for
transmission errors. It is calculated as an exclusive-OR of the header bytes and the message bytes.
Each FSK bit is aligned to 512 periods of the power signal. A ONE bit is represented by two transitions over the
512-period slot - the frequency change occurs at the very start of the slot and after 256 power signal periods
pass. A ZERO bit is represented by a single transition (at the start of the 512-period slot).
Figure 45. Example of differential bi-phase encoding
Each data byte is transferred as a sequence of 11-bits. The sequence consists of a start bit (ZERO), the data
byte itself, a parity bit and a stop bit (ONE). The parity used for byte encoding is even – the parity bit set to a ONE
if the data byte contains an odd number of ONE bits. If the data byte contains an even number of ONE bits, the
parity bit is set to a ZERO instead. This encoding scheme is used for all 3 parts of the FSK packet - the header,
message and checksum.
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Device description and operation
There is also an additional type of message which can be sent from the transmitter to the receiver – a response to
a receiver’s message. A response consists of 8 bits, so the receiver can use quite a simple logic to decode it. The
response can be either Acknowledge (ACK), Not-Acknowledge (NACK), Attention (ATN), or Not-Defined (ND).
ACK is encoded as a series of 8 ONE bits, NACK is encoded as 8 zero bits, ND is encoded as a series of 8 bit of
alternating ZERO and ONE bits (‘01010101’), and ATN is encoded as alternating double bits of ZEROS and
ONES ('11001100'). FSK response patterns are handled by STWLC98 firmware. If any proprietary communication
(proprietary message, DTS) is received, it will be available in the relevant register and the host MCU will be
notified by an interrupt.
Figure 46. Example of different response patterns
For a more detailed explanation please refer to the Qi Specification, Section Power Transmitter to Power Receiver
communications interface.
5.11.3
Most common Qi communication packets
•
•
•
UM3194 - Rev 1
Control Error Packet (CEP) provides feedback from the power receiver to the power transmitter about the
amount of power required by the load. CEP is a two’s complement signed integer; its maximum range is
-128 to +127. Its value is calculated by the receiver as a portion of the currently transmitted power, by
which the current power level should be increased/decreased. A negative CEP indicates less power is
required, while a positive CEP indicates more power is required. CEP equal to zero indicates no changes
of the operation point are required. This packet is handled automatically by the STWLC98 firmware.
Received power packet (RPP) value is calculated by the power receiver as a portion of the maximum
power value contained in the configuration packet and is used to inform the transmitter about the amount of
power received by the receiver. This information is mainly used for foreign object detection. This packet is
handled automatically by the STWLC98 firmware.
Signal strength packet (SS) indicates the degree of coupling between the transmitting and receiving coils.
Its value is an unsigned integer, and it is calculated from the current power/voltage level as a portion of the
maximum expected power/voltage once at the startup of the power receiver. This packet is handled
automatically by the STWLC98 firmware.
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Device description and operation
•
•
•
Proprietary packet (PP) enables sending custom messages between the transmitter and the receiver. Qi
standard defines different proprietary packet types, which can range in length from 1 to 20 bytes.
Data transport stream (DTS) is used to pass application-level data between power receiver and power
transmitter. It is capable of transferring up to 2047 bytes in one stream. This DTS is also used for
Authentication (defined in Qi specification).
End power transfer (EPT) is used by the power receiver to request power transfer termination. The power
transmitter shall terminate the power transfer immediately after receiving an EPT packet. The EPT packet
should contain a message indicating the reason for the termination. The following table lists the codes used
for various reasons.
Table 5. EPT codes
Reason
Value
Recommended usage of the values (informative)
EPT/nul
0x00
Use if none of the other codes is appropriate
EPT/cc
0x01
Charge complete; use to indicate that the battery is full
EPT/if
0x02
Internal fault; use if an internal logic error has been encountered
EPT/ot
0x03
Overtemperature, use if the battery temperature exceeds a limit (for example).
EPT/ov
0x04
Overvoltage; use if a voltage exceeds a limit
EPT/oc
0x05
Overcurrent; use if the current exceeds a limit
EPT/bf
0x06
Battery failure: use if the battery cannot be charged
EPT/nr
0x08
No response: use if the target operating point cannot be reached
EPT/an
0x0A
Aborted negotiation: use if Power Transfer Contract cannot be negotiated
EPT/rst
0x0B
Restart; use to restart the power transfer
5.11.3.1
ASK communication example: sending a proprietary packet from STWLC98 to STWBC2
A proprietary packet can be sent from STWLC98 using the GUI. To send a proprietary packet, navigate to the
[Communication] section of the Common registers.
First fill the message in the MSG SEND register. The entered data should contain a header and payload; CRC is
calculated automatically. Then execute RX SEND MSG (tick box and press [W]). RX SEND MSG is zeroed once
the operation is completed (press [R] to update value from device to check).
If a response is from Tx is expected, use SEND MSG WAIT RPLY instead of RX SEND MSG. It is recommended
to clear MSG RECV buffer (fill with zeros) before the command.
Note:
To be notified when reply is received, enable the RX MSG RECVD interrupt and make sure it is cleared before
sending the message (for more information about interrupts, please see the relevant section).
There are two ways to fill the data in the MSG SEND register:
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Device description and operation
1. The first option is to use MSG SEND GUI line.
Note:
Only the first 11 bytes can be use with this method. To work with the whole register, use the second option.
Data are filled by following order:
Zeroes for unused bytes
Data
Header
Figure 47. GUI example with header 0x48 and payload 0xA5 0x01 0x77 0xCE
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Device description and operation
2. The second option is to use the [Step Sequencer] function (in the left menu bar of the GUI), for more
information about this function, refer to GUI user manual.
Step sequencer works with a two-byte register address. To obtain this address, refer to STWLC98 datasheet.
For this example, the SEND MSG register starts at 0x0180 address.
Note:
Be sure to select the correct device (in this case, [[RX]WLC98]) and correct method (in this case, [Write])
from drop down menus.
Figure 48. Step Sequencer example with header 0x48 and payload 0xA5 0x01 0x77 0xCE
To send the message, the SEND MSG command must be executed. The I²C address can be found in device
datasheet; in this case, it is 0x0090 and it is 3rd bit
Figure 49. Step Sequencer example MSG SEND
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Device description and operation
5.11.4
Data transport stream (DTS)
Data transport stream is defined in Qi version 1.3 specification and above. DTS essentially consists of auxiliary
data control (ADC) and auxiliary data transport (ADT) packet types. Data to be sent is divided into multiple ADT
packets (from 1 to 7 bytes). The data transmitter first sends an ADC packet to specify the DTS type
(authentication or proprietary) and the total byte count for the transmission, before ADT packet transmission
commences.
To maintain power transfer, control error and other types of packets can be sent between DTS packets, but they
are not recognized as part of the DTS stream.
After all DTS packets are sent and reception is acknowledged, the data transmitter sends another ADC packet to
end the stream. Refer to the Qi specification for a more detailed description of DTS and individual packets.
In the Qi specification, the power receiver can initiate a data transport stream at any time, but if a power
transmitter wants to open a data stream or send data, it must send an ATN response to any incoming singlequery packet, and the power receiver responds via a DSR/poll packet.
Most of the steps for DTS are handled by STWLC98 firmware. To make DTS functionality available on the
STWLC98, the RX NEG bit is set to 1 (EPP in GUI). The following steps describe how to send data via DTS:
1. If not yet done, set the requirement to acknowledge reception of power packet by the transmitter (RX RPP
FORM). A second option is to set RX RP24 REPLY register to reply mode; this requires generating a new
configuration file and uploading to the device.
2. Set the byte length of data to be sent in the register (RX DTS SEND LEN)
3. Set the auxiliary data control header by writing to the register (RX DTS SEND ADC)
4. Fill the data in the DTS packet buffer (DTS SEND)
5. Clear receive buffer by filling it with zeroes DTS RECV (optional)
6. Start DTS stream by setting the register to 1 (SEND DTS)
Figure 50. Setting RPP with acknowledgment in GUI (can only be set once, not persistent on reboot)
Get digest DTS packet is chosen for this example. This packet is part of Qi authentication, so DTS SEND ADC is
set to 0x02. From the Qi specification, the payload of this packet is two bytes long and is 0x19 0x0F.
The figure below shows the Step Sequencer commands, which are numbered in the same way as the DTS step
list above. The last line/command is used to read 32 bytes of content of the Tx DTS response (in this case,
response to get digest request).
The log of each command and the results of DTS RECV buffer reads are visible on the right of the GUI window.
In case of receiving data via DTS, most of the actions are performed by STWLC98 firmware, including ATN and
DSR/poll handshake.
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Device description and operation
After STWLC98 receives a DTS, the firmware sets an interrupt bit to indicate whether stream reception was
successful or an error occurred (timeout or reset). If reception was successful, the user can read information from
following registers:
•
RX DTS RECV LEN length of received data (number of bytes)
•
RX DTS RECV ADC DTS ADC header (refer to Qi specification for its meaning)
•
DTS RECV buffer where received data are stored
Figure 51. Reading DTS buffer contents
5.12
Authentication
The Qi specification defines the authentication protocol for power receivers to authenticate power transmitters,
refer to the Qi specification for full details.
From the perspective of the power receiver, the current Qi authentication protocol (version 1.0) uses DTS to
exchange all necessary data (see Section 5.11.4: Data transport stream (DTS) on how DTS works on the
STWLC98, with an example of a get digest request).
During the authentication process, the STWLC98 only behaves as a messenger. This means that requests for all
required data (by sending appropriate DTS messages) are handled by the host (MCU). Storing and processing
data (certificates) must be performed on the host side.
The size of the STLWC98 receive buffer is limited, so some data must be requested in pieces.
5.13
ST Super Charge (STSC)
The STSC (ST Super charge) protocol developed by ST enables power transfer above 15W. This protocol uses
Qi-specified proprietary packets to exchange the necessary data between the power transmitter and power
receiver.
A quick guide for STSC with GUI can be found at the end of this document, while detailed information about
STSC can be found in the relevant application note.
5.14
Adaptive rectifier configuration (ARC) mode
ARC mode improves the ping-up and spatial freedom of the system in both X and Y directions during power
transfer, without any change in hardware or optimization of the coil. The feature mode can provide up to seven
additional millimeters of spatial freedom in the up, down, left, and right directions. The ARC mode function can be
configured to be disabled by the firmware after VRECT voltage rises above a set threshold (default 10 V), the
threshold can be configured in the GUI by the RX ARC THRES register.
UM3194 - Rev 1
page 42/94
UM3194
Device description and operation
If RX ARC EN bit is set to 0, the ARC mode is disabled once the firmware is initialized during startup without
waiting for Vrect to reach RX ARC THRES.
Figure 52. Startup waveform with ARC mode at normal Z distance
Figure 53. Startup waveform with ARC mode at high Z distance
ARC mode is a dedicated rectifier setting that increases spatial freedom of charging. When ARC mode is
deactivated, the rectifier switches to regular full synchronous operation mode.
The table below shows how ARC mode improves ping up spatial freedom.
UM3194 - Rev 1
page 43/94
UM3194
Device description and operation
Table 6. Possible separation without and with ARC mode
Separation (mm)(1)
Ping without ARC mode
Ping with ARC mode
2
OK
OK
4
OK
OK
8
OK
OK
12
OK
OK
16
Cannot ping up
OK
18
Cannot ping up
OK
19
Cannot ping up
OK
20
Cannot ping up
Cannot ping up
1. Defined as coil to coil distance
5.15
Transmitter (Tx) mode
The STWLC98 dual wireless power receiver can also function as a wireless power transmitter. Full details on
wireless transmitter (RTx) mode operation are, however, beyond the scope of this user manual.
The transmitter mode allows low power transmission for charging wearables and similar products requiring
relatively small amounts of charging power.
Figure 54. STWLC98 Transmitter mode schematic
UM3194 - Rev 1
page 44/94
UM3194
Device description and operation
To operate in the transmitter mode, the device requires an external ASK demodulation circuit. The demodulation
circuit can be seen in the figure above (labeled TX mode only). This circuit is essential for ASK communication
demodulation, as communication from the receiver to the transmitter is crucial in establishing a regulation loop.
Note:
Transmitter mode is not supported by default. Please contact local ST support team if the TX mode
implementation is required.
5.16
I²C Interface
STWLC98 can operate fully independently, without being interfaced with a host system. In applications in which
the STWLC98 is a part of peripherals managed by the host system, the two SDA and SCL pins may be connected
to the existing I²C bus. The device works as an I²C secondary device and supports standard (100 kbps), fast (400
kbps), and fast mode plus (1Mbps) data transfer modes.
STWLC98 is assigned the 0x61 7-bit hardware address.
The pins are up to 1.8 V tolerant, and the pull-up resistors should be selected as a trade-off between
communication speed (lower resistors lead to faster edges) and data integrity (the input logic levels must be
guaranteed to preserve communication reliability). When the bus is idle, both SDA and SCL lines are pulled
HIGH.
5.16.1
Data validity
The data on the SDA line shall remain stable during the high state of every SCL clock pulse. The high and low
states of the SDA line shall only change when the SCL clock signal is low.
5.16.2
Start and stop conditions
Both the SDA and the SCL lines remain high when the I²C bus is not busy. A START condition is indicated by a
high-to-low transition of the SDA line when SCL is HIGH, while the STOP condition is indicated by a low-to-high
transition of the SDA line when SCL is HIGH. A STOP condition must be sent before each START condition.
5.16.3
Byte format
Every byte transferred over the SDA line contains 8 bits. Each byte received by STWLC98 is generally followed
by an acknowledge (ACK) bit. The most significant bit (MSB) is transferred first. A single data bit is transferred
during each clock pulse.
The device generates an ACK pulse (by pulling the SDA line low during the acknowledge clock pulse) to confirm a
correct device address or data byte reception.
5.16.4
Interface protocol
The interface protocol consists of:
•
•
•
•
•
•
A start condition (START)
A device address + R/W bit (read =1 / write =0)
A register H address byte
A Register L address byte
A sequence of n data bytes (each data byte must be acknowledged by the receiver)
A stop condition (STOP)
The register address byte determines the first register in which the read or write operation takes place. When a
read or write operation is finished, the register address is automatically incremented.
5.16.5
Writing to a single register
Writing to a single register begins with a START condition followed by the device address 0xC2 (7-bit device
address plus R/W bit cleared), two bytes of the register pointer and the data byte to be written in the destination
register. Each transmitted byte is acknowledged by the STWLC98 through an ACK pulse.
UM3194 - Rev 1
page 45/94
UM3194
Device description and operation
Figure 55. Writing to a single I²C register
5.16.6
Writing to multiple registers with incremental addressing
STWLC98 supports writing to multiple registers with auto-incremental addressing. When data is written into a
register, the register pointer is automatically incremented, therefore transferring data to a set of subsequent
registers (also known as page write) is a straightforward operation.
Figure 56. Writing to multiple I²C registers
5.16.7
Reading from a single register
Reading from a single register begins with a START condition followed by the device address byte 0xC2 (7-bit
device address plus R/W bit cleared) and two bytes of register pointer, then a restart condition is generated and
the device address 0xC3 (7-bit device address plus R/W bit asserted) is sent, followed by data reading. ACK
pulse is generated by the STWLC98 at the end of each byte, but not for data bytes retrieved from the register. A
STOP condition is finally generated to terminate the operation.
Figure 57. Reading from a single I²C register
UM3194 - Rev 1
page 46/94
UM3194
Device description and operation
5.16.8
Reading from multiple registers with incremental addressing
Similarly, to multiple bytes (page) writing, reading from subsequent registers relies on an auto-increment of the
register: The master can extend data reading to the following registers by generating and an ACK pulse at the
end of each byte. Data reading starts immediately, and the stream is terminated by a NMAK at the end of the last
data byte, followed by a STOP condition.
Figure 58. Reading from multiple I²C registers
5.17
GPIOx and INTB pins
GPIO0 through GPIO5 are programmable general-purpose I/O pins. These pins can be configured as inputs or
outputs (push-pull or open-drain) and assigned various functions.
Table 7. Available functions on GPIO pins
Code
I/O
Type
Function
Code
I/O
Type
Function
0x00
In
Floating
No function (GPIO configured as input floating)
0x01
In
Pull-up
No function (GPIO configured as input pull-up)
0x02
In
Pull-down
No function (GPIO configured as input pull-down)
0x03
Out
Push-Pull
No function (GPIO configured as output drive low)
0x04
Out
Push-Pull
No function (GPIO configured as output drive high)
0x05
Out
Open drain
Interrupt, internal pull-up (0=active, 1=inactive)
0x06
Out
Push-Pull
Interrupt (0=active, 1=inactive)
0x07
Out
Push-Pull
High on FW ready
0x08
In
Pull-down
Main LDO block (0=unblock, 1=block)
0x09
In
Pull-down
Rx stop ASK communication (0=unblock/unstop, 1=block/stop)
0x0A
Out
Push-Pull
Power output enabled (0=off. 1=on)
0x0B
Out
Open drain
Power output enabled (0=off. 1=on)
0x0C
Out
Push-Pull
Power negotiated (0=off, 1=on)
0x0D
Out
Open drain
Power negotiated (0=off, 1=on)
The INTB (GPIO6) pin is, by default, an interrupt output line which is assigned to any enabled internal interrupt
condition and used to inform the host system about a specific event.
5.18
Interrupt registers
There are 4 bits (enable, clear, latch, and status) assigned to each interrupt sorted into separate tabs.
The enable tab can be used to either enable the corresponding interrupt (write), or to check whether the interrupt
is already enabled (read). The enable state is updated immediately and can be saved to the configuration file.
The latch tab can be used to determine which interrupts have been triggered (read only). After being triggered,
the bit remains set to 1 until cleared by writing a 1 into the corresponding clear register (write only). The clear
register is cleared automatically.
UM3194 - Rev 1
page 47/94
UM3194
Device description and operation
The status tab can be used to determine which interrupt is being triggered at a given moment (read only). The
status bit returns to zero after the triggering condition is removed.
All clear, Latch and Status register values are lost upon device reboot.
Figure 59. Interrupt register settings
Table 8. Interrupt description
UM3194 - Rev 1
Interrupt label
Description
RX DTS RCVD RESET END
DTS receiving stopped due to reset by ADC (Auxiliary Data Control), refer to Qi specification for
more details
RX DTS RCVD SUCCESS
DTS stream successfully received
RX DTS RCVD TO END
DTS receiving stream stopped due timeout
RX DTS SEND RESET END
DTS sending stopped due to reset by ADC (Auxiliary Data Control), refer to Qi specification for
more details
RX DTS SEND SUCCESS
DTS stream successfully sent
RX DTS SEND TO END
DTS stream sending stopped due timeout
RX EXT 5V FAULT
Failure during connection or disconnection of external 5 V.
RX MSG RECVD
Proprietary packet received
RX OCP
Triggered by OCP protection or ADC OCP protection, for details see Protections overview
section.
RX OUTPUT OFF
Output disabled (main LDO turned off)
RX OUTPUT ON
Output enabled (main LDO turned on)
RX OVP
Any enabled over voltage protection has triggered: OVPS, OVPH, ADC OVP, VOUT OVP. For
more information about individual protections refer to Protections overview section.
RX OVTP
Triggered by any over temperature protection: ADC OVTP (chip internal), TSHUT (chip internal)
or NTC protection. For details see Protections overview section.
RX SCP
Triggered by output short current protection (SCP). For details see Protections overview
section.
RX SEND PTK TO
Response for proprietary packet not received (timeout)
RX SIG STR
Signal strength packet received
page 48/94
UM3194
Device description and operation
Interrupt label
UM3194 - Rev 1
Description
RX SYS ERROR
STWLC98 internal error occurred, please in GUI check Common registers → System error info
tab for more details
RX TX REMOVAL
Power receiver removed from power transmitter or power transmitter removed power. Useful
when STWLC98 powered by external 5 V.
RX VRECT RDY
Vrect voltage reaches sufficient value for enabling Vout
page 49/94
UM3194
STEVAL-WLC98RX description and operation
6
STEVAL-WLC98RX description and operation
6.1
Schematic diagrams
Figure 60. STEVAL-WLC98RX circuit schematic
UM3194 - Rev 1
page 50/94
UM3194
STEVAL-WLC98RX description and operation
6.2
Bill of materials
Table 9. STEVAL-WLC98RX bill of materials
Item
Q.ty
Ref.
17
TP1, TP2,
TP3, TP4,
TP5, TP6,
TP7, TP8,
TP9,
TP10,
TP11,
TP12,
TP16,
TP17,
TP18,
TP19,
TP20
SMD TP 2mm
Harwin
S2751-46R
10
C1, C2,
C3, C4,
C20, C23,
C25, C27,
C29, C30
100n,
C_SMD_0603_DIN1608M
_IR, 50 VDC
Wurth
885012206095
3
7
P2, P3,
P7, P8,
P16, P17,
P19
HDR1X2
Harwin
M20-9990245
4
5
C16, C17,
C18, C19,
C21
10u,
C_SMD_0805_DIN2012M
_IR, 50 VDC
Murata
GRM21BR61H106KE
43L
5
5
P11, P12,
P13, P14,
P15
P_PTH_TP_P12D06_SO
LD_T-B+
(not assembled) Any
Any
6
4
D4, D5,
D6, D7
DIOMELF1006N
(not assembled) Any
1N4448HLP-7
7
4
TP13,
TP14,
TP15,
TP21
SMD TP 2mm,
J_2mm_HOOK
(not assembled) Any
S2751-46R
8
3
C13, C14,
C15
4n7,
C_SMD_0603_DIN1608M
_IR, 50 VDC
9
3
4k7,
R7, R8, R9 R_SMD_0603_DIN1608M
_IR, 100mW
10
2
C7, C8
11
2
12
13
1
2
UM3194 - Rev 1
Value
Description
Manufacturer
Part number
Wurth
885012206087
YAGEO
RC0603FR-074K7L
47n,
C_SMD_0603_DIN1608M
_IR, 50 VDC
Wurth
885012206093
C9, C10
22n,
C_SMD_0603_DIN1608M
_IR, 50 VDC
Wurth
885012206091
2
C11, C12
10n,
C_SMD_0603_DIN1608M
_IR, 50 VDC
Wurth
885012206089
2
C24, C26
1u,
C_SMD_0603_DIN1608M
_IR, 16 VDC
Wurth
885012206052
page 51/94
UM3194
STEVAL-WLC98RX description and operation
UM3194 - Rev 1
Item
Q.ty
Ref.
Value
Description
Manufacturer
14
2
C32, C33
10n,
C_SMD_0603_DIN1608M (not assembled) Any
_IR
885012206089
15
2
D1, D2
G_SMD_SMA_DO-214AC
_UNIPOLAR
Littelfuse
SMAJ22A
16
2
J1, J2
J_PTH_BANAN
A2MM
Cinch
Connectivity
Solutions
105-0751-001
17
2
R1, R2
100R,
R_SMD_0805_
DIN2012M_IR,
500mW
Panasonic
ERJ-UP6J101V
18
2
R3, R4
(not assembled)
47R,
R_SMD_0805_
DIN2012M_IR,
500mW
Panasonic
ERJ-UP6J470V
19
1
C5
C_SMD_0603_DIN1608M
_IR
Any
Any
20
1
C6
3n3,
C_SMD_0603_DIN1608M (not assembled) Wurth
_IR, 50 VDC
885012206086
21
1
C22
C_SMD_0805_DIN2012M
_IR
Any
Any
22
1
C28
4u7,
C_SMD_0603_DIN1608M
_IR, 10 VDC
Wurth
885012106012
23
1
C31
470p,
C_SMD_0603_DIN1608M (not assembled) Any
_IR, 50 VDC
24
1
C34
(not assembled) Any
25
1
C35
680p,
C_SMD_0603_DIN1608M (not assembled
_IR
Any
885012206082
26
1
C39
100n,
C_SMD_0603_DIN1608M (not assembled) Any
_IR
885012206095
27
1
D3
Q_SMD_LED_0603_DIN1
608M, 2 VDC, 20mA
Wurth
150060RS75000
28
1
D8
D_SOD523 20 VDC, 1A
Nexperia
PMEG2010AEBF
29
1
J4
J_PTH_BANANA2MM
Cinch
Connectivity
Solutions
105-0753-001
30
1
J5
J_PTH_BANANA2MM
Cinch
Connectivity
Solutions
105-0752-001
31
1
JP1
P_solderingoption_02_v3
Any
Any
32
1
JP2
P_solderingoption_02_v3
(not assembled) Any
Any
33
1
JP1
HDR1X4
Harwin
M20-9990445
34
1
JP4
HDR1X6
Harwin
M20-9990645
35
1
P5
HDR1X8
Harwin
M20-9990845
36
1
P6
HDR1X5
Harwin
M20-9990545
37
1
P18
HDR1X2
(not assembled) Any
Part number
m885012206081
885012206091
M20-9990245
page 52/94
UM3194
STEVAL-WLC98RX description and operation
6.3
Item
Q.ty
Ref.
Value
Description
Manufacturer
38
1
Q1
SOT23A
39
1
R5
15k,
R_SMD_0603_DIN1608M
, 100mW
Yageo
RC0603FR-0715KL
40
1
R6
220R,
R_SMD_0603_DIN1608M
_IR, 100mW
Yageo
RC0603FR-07220RL
41
1
R10
100k,
R_SMD_0603_DIN1608M (not assembled) Any
_IR
AC0603FR-07100KL
42
1
R11
0R,
R_SMD_0603_DIN1608M (not assembled) Any
_IR
RC0603JR-070RL
43
1
R12
75R,
(not assembled) Any
R_SMD_0603_DIN1608M
RC0603FR-0775RL
44
1
R13
5k1,
(not assembled) Any
R_SMD_0603_DIN1608M
RC0603FR-0775RL
45
1
R14
220k,
(not assembled) Any
R_SMD_0603_DIN1608M
RC0603FR-07220KL
46
1
R15
10k,
(not assembled) Any
R_SMD_0603_DIN1608M
RC0603FR-0710KL
47
1
U1
WLCSP90
ST
STWLC98JR
48
1
Spacer,
part A and
Part B
Spacer/STEVAL-WLC98
UL-94 V0 or V1
certified
material
Any
Any
49
4
Standoff
M3x20mm
Wurth
970200365
50
4
Screw with
flat head
M3x8mm flat
head
Essentra
components
50M030050I008
51
4
Screw
M3x6mm
Essentra
components
50M030050P006
52
1
Coil
Luxshare
Luxshare
LD81FP008-1H
53
1
Wires for
coil
CNC tech
610220
54
1
Glue
Loctite
Loctite 454
(not assembled) Any
Part number
DMP6350S
STEVAL-WLC98RX coil description
Table 10. Electrical characteristics of the receiver coil
Parameter
UM3194 - Rev 1
Specification
Part number
LD81FP008-1H
Vendor
Luxshare-ICT
Inductance (@ 100 kHz)
8 ±0.2 µH
DC resistance (DCR)
190mΩ (±10%)
AC resistance (ACR)
225mΩ (±10%)
page 53/94
UM3194
STEVAL-WLC98RX description and operation
Figure 61. Mechanical characteristics of the receiver coil 1
Figure 62. Mechanical characteristics of the receiver coil 2
UM3194 - Rev 1
page 54/94
UM3194
STEVAL-WLC98RX description and operation
Figure 63. Mechanical characteristics of the receiver coil 3
6.4
STEVAL-WLC98RX PCB layout
Figure 64. STEVAL-WLC98RX PCB layout top layer
UM3194 - Rev 1
page 55/94
UM3194
STEVAL-WLC98RX description and operation
Figure 65. STEVAL-WLC98RX PCB layout inner 1 layer
Figure 66. STEVAL-WLC98RX PCB layout inner 2 layer
UM3194 - Rev 1
page 56/94
UM3194
STEVAL-WLC98RX description and operation
Figure 67. STEVAL-WLC98RX PCB layout bottom layer
UM3194 - Rev 1
page 57/94
UM3194
STEVAL-WLC98RX description and operation
6.5
STWLC98 default configuration
Table 11. STWLC98 default configuration
Parameter
Output voltage (BPP mode, 5 W)
5V
Output voltage (EPP mode, 15 W)
12 V
Guaranteed power (BPP)
5W
Guaranteed power (EPP)
15 W
Guaranteed power (STSC)
50 W
Input voltage loop (IVL)
Disabled
Firmware overcurrent protection (ADC OCP)
2.7 A
Soft overvoltage protection stage 1 (SOVP1)
24 V
Soft overvoltage protection stage 2 (SOVP2)
25 V
Firmware overtemperature protection (ADC OVTP)
95°C
Hardware overtemperature protection (TSHUT)
115°C
Iload
40 mA
ARC mode disable threshold
10 V
Manufacturer ID
I²C address
Vout setting +80 mV
0x0016
0x61 (7-bit address)
16-bit register address
high-byte first
low-byte second
Frequency band: 140.6–142.9 kHz;
H-field: -5.17dBµA/m at 10 m (for EU/UK)
•
LDO setting (output current dependent):
•
–
Highest LDO drop: 320 mV
–
Lowest LDO drop: 144 mV
Active interrupts:
•
–
Message received from TX
–
OCP (overcurrent) protection
–
RX Output on
–
OVP (overvoltage) protection
–
OVTP (overtemperature) protection
–
Short-circuit protection
–
Ext 5 V Tx removal
GPIO functions:
–
–
UM3194 - Rev 1
4V
Hardware overcurrent protection (HW OCP)
Vrect ready threshold (Vout is enabled)
Note:
Value
GPIO6 as Interrupt
other GPIOs: no function
page 58/94
UM3194
STEVAL-WLC98RX description and operation
6.6
Typical performance characteristics
Board specifications as defined before (see Reference design specifications)
6.6.1
Power up waveforms
The following figure shows the power up waveforms (receiver side) of a STWLC98 (RX) and STEVAL-WBC2TX50
(TX) setup. The transmitter and receiver coils are aligned; a 500-mA resistive load is connected to the receiver
output.
Figure 68. Power up waveforms of a STEVAL-WLC98RX (Rx) and STEVAL-WBC2TX50 (Tx) setup
6.6.2
Efficiency and spatial freedom in the XY plane
Efficiency is one of the most important metrics of wireless charging performance evaluation. Spatial freedom, size
of the area in which a power receiver can be placed on the power transmitter which still allows sufficient power to
be transmitted, is another important metric.
Efficiency and spatial freedom of STEVAL-WLC98 were measured with STEVAL-WBC2TX50 as the transmitter.
The efficiency was measured from the transmitter DC input to the receiver DC output. The measurement does not
include any power losses in the wall adapter or the cable.
The test setup consisted of:
•
•
•
•
•
•
•
UM3194 - Rev 1
Wall adapter Baseus GaN Mini Quick Charger 120 W, model CCGAN120E
USB-C power cable from Vention, model COT
STEVAL-WBC2TX50
STEVAL-WLC98RX as the receiver
Electronic load in CC mode, model BK Precision 8500
STEVAL-USBI2CFT converter to perform STSC commands
Power transmitter input voltage 20 V, power receiver output voltage 20 V
page 59/94
UM3194
STEVAL-WLC98RX description and operation
Figure 69. Efficiency curves for various misalignments in the X-axis
6.6.3
Spatial freedom in the Z-axis
Z-axis distance between the coils, also known as charging gap, is an additional parameter which significantly
affects charging performance. Therefore, STEVAL-WLC98RX was also tested at various charging gap distances.
The measurements examined two key performance indicators – efficiency and maximum delivered power.
Figure 70. Efficiency curves for various misalignments in the Z-axis
UM3194 - Rev 1
page 60/94
UM3194
STEVAL-WLC98RX description and operation
Table 12. Maximum power for Z-axis gaps
Z gap [mm]
Maximum power [W]
4
50.0
6
50.0
8
50.0
11
50.0
15
50.0
17
43.9(1)
1. Limitation due to USB-PD power adapter capability 20V/5A
ARC mode also improves performance at higher Z-axis distances. The following waveform shows how STWLC98
is able to establish communication even at a high Z-distance (19 mm), and after reaching the default 10 V VRECT
threshold, switches to a different operating mode where output can be enabled.
Figure 71. STWLC98 communication performance at high Z distances
UM3194 - Rev 1
page 61/94
UM3194
STEVAL-WLC98RX description and operation
6.6.4
Thermal performance
All thermal images were taken at 25°C ambient temperature.
Figure 72. Thermal performance with a 5 W load (5 V/1 A) after 5 minutes
Figure 73. Thermal performance with a 15 W load (12 V/1.25 A) after 5 minutes
UM3194 - Rev 1
page 62/94
UM3194
STEVAL-WLC98RX description and operation
Figure 74. Thermal performance with a 50 W load (20 V/2.5 A) after 5 minutes
UM3194 - Rev 1
page 63/94
UM3194
Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
7
Designing an up to 50 W wireless power receiver based on the
STEVAL-WLC98RX evaluation board
The design should begin with external component selection, which can have a significant impact on the board
performance. Modifications of the external components are also harder to implement after the board is
manufactured and assembled.
7.1
External component design
STWLC98 requires only a few external components to work properly. The design should begin with coil and series
resonant capacitor selection, as these are crucial design elements that have the greatest impact on device
functionality.
7.1.1
Coil selection
Coil selection is complex as there are several factors which influence the resulting performance. When selecting
the coil, the designer should consider the coil inductance, DCR, ACR, current rating, dimensions, maximum zdistance and layout.
DCR, ACR (DC and AC resistance) should be kept as low as possible to minimize power loss caused by the
current flowing through the coil.
Dimensions, maximum z-distance and coil layout must be considered to achieve the best coupling possible, as
better coupling results in higher efficiency. Similar sized coils might offer a higher coupling factor, on the other
hand a different sized RX/TX coil might offer greater freedom of positioning.
Using the default coil combination found in ST evaluation kits should be a good starting point. For more
information regarding coil selection, please refer to Coil selection guide.
7.1.2
Series and parallel resonant capacitor selection
Selection of the series and parallel capacitors is greatly influenced by the transmitting coil design. The value
should be selected so that the resulting circuit has its resonant peak located at, or very close to, 100 kHz. The
following formula can be used to calculate the series capacitance value:
f = 2 ⋅ π ⋅1 L ⋅ C
C=
1
L⋅ 2∙π∙f
2
The parallel capacitance can be omitted, as it is only used for backwards compatibility with certain power
transmitters (required during Qi certification). It may, in theory, be omitted if Qi certification is not required.
Voltage rating of the capacitors should consider that during operation, voltage generated across the capacitors is
usually much higher than the input/output voltage of the system. Also, a quick movement of the receiving coil from
a misaligned position to the transmitting coil center may generate a voltage peak, as the regulation loop is quite
slow. Therefore, the minimum recommended voltage rating of the series resonant capacitors is 50 V. X5R/X7R
dielectric capacitors are recommended if price is the deciding factor, C0G dielectric capacitors are recommended
for better performance (lower derating caused by voltage biasing and temperature shift).
For more information regarding capacitor value selection, please refer to Wireless Power Consortium
documentation, which describes capacitors used in the Qi certified topologies.
7.1.3
VRECT and VOUT capacitor selection
VRECT and VOUT capacitor value selection is mostly a tradeoff between load transition response time and
capacitor cost and/or size. A capacitance of 20-30 µF for each of the nodes should be a good starting point.
The VRECT capacitor voltage rating should respect the maximum input voltage. Voltage peaks generated by
quick coil movements should also be a concern when determining the voltage rating. Leaving a greater margin is
advisable. The VOUT capacitor voltage rating is determined by the selected output voltage. Ceramic X5R or X7R
(preferred) dielectric capacitors are recommended for both VRECT and VOUT.
Capacitor derating caused by temperature shift and DC bias should also be considered, as the capacitance
decrease caused by those effects may be quite significant. Refer to the capacitor datasheet for more information.
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
7.1.4
ASK modulation capacitor selection and configuration
STEVAL-WLC98RX features the following pairs of modulation capacitors, with each pair having a different
capacitance value: 10 nF for COMA, 22nF for COMB, and 4.7 nF for COMC.
The modulation capacitors used in STEVAL-WLC98RX were chosen to ensure good communication performance
under all operating conditions. Using a custom board design may require changing the COMA, COMB, and
COMC capacitors.
The COMx capacitors are used for power signal modulation. Although the modulation period is short, the voltage
drop it creates across the LDO must be considered, as this drop further increases overall losses of the system.
This is particularly important when the device is delivering a high load current.
The GUI allows the customer to enable a particular pair to be active during low output current operation, while
using the other and/or same during high current operation. The same can be set for low/high VRECT voltage
condition. Therefore, nine separate capacitor combinations can be selected in total.
For each of nine combinations, there is the possibility of running them normal or inverted mode.
In normal mode, communication switch is normally open (capacitor is disconnected). Communication switch will
only close (short communication capacitor to ground) only during modulation.
In inverted mode, the communication switch is instead always closed (communication capacitor shorted to
ground) and communication switch is open only when modulation is needed.
Figure 75. Rx ASK configuration
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Table 13. Default STWLC98 ASK configuration
Low Current (LC)
Low Voltage (LV)
Threshold (low)
Middle Voltage (MV)
High Voltage (HV)
Middle Current (MC)
Threshold (high)
High Current (HC)
COMA enabled
COMA enabled
COMA enabled
COMB enabled
COMB enabled
COMB enabled
COMC disabled
COMC enabled
COMC enabled
8V
8V
8V
COMA enabled
COMA enabled
COMA disabled
COMB disabled
COMC disabled
Threshold (high)
Threshold (low)
600 mA
COMB disabled
COMC disabled
1200 mA
COMB enabled
COMC disabled
16 V
16 V
16 V
COMA disabled
COMA disabled
COMA disabled
COMB disabled
COMB enabled
COMB enabled
COMC enabled
COMC disabled
COMC enabled
The following waveforms show an example of RX VRECT, COM A, COM B, COM C (Rx communication
capacitors). The figures show how the modulation capacitors affect the Vrect voltage on Rx and coil voltage sense
on coupled Tx.
The modulation effect is considered in regard to the overall power loss, as the LDO voltage drop (Vrect-Vout)
multiplied by the output current adds additional power loss into the system.
Changing the modulation capacitor value may have an impact on the TX coil voltage sense. This voltage is used
as the input for the ASK demodulation circuit. The impact depends on various variables, such as coil, coil-to-coil
distance, voltage, transferred power, misalignment, and other parameters.
This should be considered when configuring the LDO drop curve (refer to section LDO configuration).
Figure 76. Example of waveform with no output load, COM A enabled, COM B and COM C disabled
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Figure 77. Example of waveform with 1200 mA output load, COM A and COM B enbaled, COM C disabled
7.1.5
SOVP clamp resistor selection
SOVP clamp resistors, also known as IEXT resistors, are used as a part of the SOVP protection. When triggered,
STWLC98 pulls VRECT to ground through those resistors in an attempt to lower the VRECT voltage. Therefore,
the resistance value must be selected according to the selected SOVP threshold and power dissipation
capabilities of the resistors. IEXT pins’ current capabilities must also be considered, as the internal switches can
only withstand up to 300 mA of current.
7.1.6
ESD/TVS diodes
STEVAL-WLC98 also features two external TVS diodes which protect the STWLC98 input pins (AC1 and AC2)
against excessive input voltage. The breakdown voltage of those diodes is 24.4 V.
7.1.7
NTC thermistor connection
The figure below shows external NTC connection. Together with the Rhs (R7) pull-up resistor the NTC forms a
voltage divider, which is connected to the STWLC98 NTC pin. It is recommended to design the voltage divider to
reach the (low) NTC threshold at the highest allowed temperature.
Even though the NTC pin is 1.2 V tolerant, the maximum sampled voltage by the internal ADC is 0.9 V, which
must be considered during NTC and pull-up resistor selection.
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Figure 78. External NTC connection
7.2
PCB layout guidelines
•
•
•
•
•
•
•
•
•
7.3
Power tracks (AC1, AC2, VRECT, VOUT) and power ground tracks should be kept wide enough to sustain
high current. Duplicating these tracks in inner layers and adding vias is advisable wherever possible to
lower impedance as much as possible.
AC1, AC2, BOOT1, BOOT2, COMAx, COMBx, and COMCx nodes generate noise. Using shielding near
those signal tracks (by placing ground planes below) is recommended.
Power ground carries the sum of ripple current from VRECT/Crect and DC current from VOUT/Load.
Current return paths from LDO capacitors should be routed separately from the high current paths.
AC1 and AC2 tracks should be routed close together to minimize the area of the resulting loop.
Communication (I²C) and sensing signals should be routed far from noise generating nets (AC1, AC2,
COMAx, COMBx, COMCx, BOOT) to minimize the effects of interference induced from those high di/dt
nets.
COMAx, COMBx, COMCx, BOOT1, and BOOT2 capacitors should be placed as close to the device as
possible.
VRECT and VOUT capacitors should be placed close to the device to minimize the area of high current
loops.
Auxiliary LDO capacitors should be placed as close to the device as possible.
Thermal performance and grounding can be enhanced by dedicating one layer as a ground plane. No
signal/power tracks should be routed on this layer to maximize ground integrity.
LDO configuration
Configuration of the LDO has a major impact on efficiency, as it directly affects the magnitude of the power loss
created by the passing current. Therefore, minimizing the voltage drop is desired when aiming for higher
efficiency.
However, a higher LDO drop improves communication stability and helps prevent negative modulation, which
might leak into the output voltage. Lastly, different rectifier operating modes also affect the VRECT waveform.
Therefore, LDO drop configuration is a tradeoff between efficiency and communication/output voltage stability.
During LDO drop selection, the minimum achievable voltage drop due to electrical limitations (internal resistance)
must be taken into account. For STWLC98, the internal resistance is 50 mΩ, so the minimal LDO drop for a
maximum current in a given segment is calculated using following formula:
VDROPmin mV = 50 ∙ Imax A
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Figure 79. Default LDO configuration
Figure 80. Default LDO drop curve
7.4
External 5V provision
When using the STWLC98 in high power applications with output voltage (Vout) close to 20 V, the voltage drop on
the internal LDO to derive the system 5 V may provoke high chip temperatures on the IC. To prevent this, an
external 5 V can be used to supply internal 5 V power rail.
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
7.4.1
Conditions for using external 5V
•
•
•
•
•
•
Connection and disconnection of the external 5 V must follow the procedure below.
External 5 V is provided to the V5V0 pin of STWLC98 or V5V0 header (P7) of the STEVAL-WLC98.
The final product must implement a host-controlled switch to connect and disconnect external 5 V power
supply rail to STWLC98’s 5 V internal power supply rail.
If STWLC98 is removed from Tx or Tx power is removed (for example by EPT or FOD reason) the host
must disconnect the external 5 V from the STWLC98. Removal of STWLC98 from Tx if external 5 V is used
is signaled by the RX TX REMOVAL interrupt.
STWLC98 startup is possible only with 5 V internal LDO.
The supply circuit of the external 5 V to STWLC98 should be able to deliver 70 mA. This value can
increase if there is an external circuit using, for example, 1V8 from the STWLC98 internal LDO.
Before starting, it is highly recommended to enable the following interrupts and protections:
•
•
•
RX TX REMOVAL interrupt: the interrupt informs the host MCU that power from PTx was removed.
External 5V must be disconnected upon interrupt, effectively powering down the STWLC98.
RX EXT 5V FAULT interrupt: the interrupt informs that the issue occurred during the process of connection
or disconnection of the external 5V.
Rx UVLO protection (RX UVLO PROT EN register) with the RX UVLO VOUT OFF option to ensure correct
load disconnection once PTx power is removed.
Figure 81. Recommended interrupts to enable for using external 5 V
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Figure 82. Recommended protection setting for using external 5 V
Procedure for connection of external 5 V to STWLC98:
1. Host writes 0x01 to RX EXT 5V ON register (address 0x0091)
2. STWLC98 lowers its internal LDO voltage to 4.2 V and clears RX EXT 5V ON register.
3. Once RX EXT 5V ON register is self-cleared, there is a 100 ms interval for the host to provide an external 5 V
to the STWLC98
If connection is successful, the STWLC98 is powered from the external 5 V supply and its internal LDO is
disabled. If connection is unsuccessful, the EX EXT 5V FAULT interrupt is raised and the host must remove the
external 5 V supply. Before the host attempts this connection procedure again, it must clear the RX EXT 5V
FAULT interrupt.
Procedure for disconnection of external 5 V from STWLC98:
1. Host writes 0x02 to RX EXT 5V OFF register (address 0x0091)
2. STWLC98 enables internal LDO with voltage of 4.2 V and clears RX EXT 5V OFF register.
3. Once RX EXT 5V OFF register is cleared there is a 100 ms interval for the host to remove external 5 V from
the STWLC98.
If disconnection is successful, STWLC98 changes internal LDO voltage back to 5 V and is powered by internal
LDO. If disconnection is unsuccessful (host did not disconnect 5 V supply), the EX EXT 5V FAULT interrupt is
raised and the STWLC98 internal LDO is disabled. Before the host attempts this disconnection procedure again, it
must clear RX EXT 5V FAULT interrupt.
Improper disconnection of external 5 V when the internal LDO is disabled will cause a reset of the STWLC98 and
interrupt power transfer.
7.5
FOD tuning guide
The STWLC98 uses a precise internal AD converter to perform voltage and current measurements and 32-bit
arithmetic to ensure sufficient accuracy. The IC then uses the measured values to create a mathematical model to
estimate the received power, which is sent to the power transmitter for evaluation.
To ensure that the mathematical model is sufficiently precise, the STWLC98 needs to account for power loss in
the system. The FOD parameters used in the estimation can be used to fine-tune the calculation results based on
the required behavior.
As system losses can be influenced by various factors like coil type, PCB layout, and the mechanical structure of
the final product (screws and metal structures near coils), FOD parameter adjustment (FOD tuning) must be
performed with the final product.
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
The process for tuning FOD in Qi BPP and Qi EPP mode is described below. For tuning in high power
applications with STSC, refer to the FOD tuning application note. A quick method using the STEVAL-WBC2TX50
as PTx is also described below.
The operating point may also have an impact on power loss. Different loads (different output currents) are
covered by segmenting the FOD parameters into six current segments. There are several groups of FOD
parameters available:
RX FOD Configuration BPP is used to store FOD parameters in non-volatile memory for operation in Qi BPP
mode.
RX FOD Configuration EPP is used to store FOD parameters in non-volatile memory for operation in Qi EPP
mode.
After STWLC98 power up, content of one of these groups is copied to the Rx FOD Configuration LIVE
parameter group according to the operation mode. Values in the Rx FOD Configuration LIVE group are
used for received power calculations during power transfer. The values can be updated during run time, but
changes are lost on reboot.
If the application needs to use a high power mode like STSC mode, the FOD parameters are no longer stored in
STWLC98 memory. FOD parameters must be tuned for each step in the STSC sequence and stored in host MCU
memory. Immediately after the host MCU performs an STSC voltage change step, it must update the FOD
parameters in the STWLC98 I²C register. During STSC, the Rx FOD Configuration LIVE parameter group is
used.
The first parameter to be set is RSER, after which the power compensation curve should be tuned.
7.5.1
RSER
The RSER value corresponds to the resistance of the receiving coil and other resistive losses (PCB, cables, etc.).
Power loss is calculated as FOD RSER times the output current squared. The result is then added to receive the
power modification value defined by the compensation curve (see below).
FOD RSER is valid for whole load current range. The RSER value is found in the GUI as the FOD RSER register.
7.5.2
Power compensation curve
The Power compensation curve is defined by FOD OFFSETx. To facilitate tuning, the full range of loads (output
currents) is divided into six segments bounded by FOD CUR THRx. FOD OFFSETx is defined for each FOD CUR
THRx (FOD CUR THR0 is defined for 0 mA).
Two boundary FOD OFFSETx values define a linear power compensation dependency on the output current for a
given segment, see Figure 83. The power compensation value coming from this algorithm is added to the
received power from STWLC98 together with RSER, and it is sent in a receive power packet (RPP) to the power
transmitter.
Figure 83. FOD offset defined modification of receive power, example diagram
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
7.5.3
BPP FOD tuning
Before proceeding, prepare Qi compliant BPP power transmitter capable of reporting transmitted power.
Step 1.
Set all FOD tuning (RX FOD Configuration BPP) parameters to zero:
Step 1a. place the STWLC98 on the power transmitter and wait for power transfer.
Step 1b. locate the [Rx FOD Configuration BPP] tab and set all parameters to zero
Figure 84. Cleared BPP FOD tuning registers
Step 2.
Generate the new configuration file and write to STWLC98.
Step 3.
Navigate to the [RX FOD Tuning tab] in the GUI to open the FOD tuning tool.
Figure 85. Rx FOD tuning update table line
UM3194 - Rev 1
Step 4.
Place the STWLC98 onto a Qi compliant power transmitter.
Step 5.
Connect the electronic load to the STWLC98 output (VOUT) and read the received power (value held
in POWER RX register in [Common Registers]>[Mode Monitor]) and output current power (value held
in ICUR register in [Common Registers]>[Mode Monitor]). Write both values to the FOD tuning table.
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Step 6.
Read the transmitted power values from the Qi compliant power transmitter and write it to the GUI FOD
tuning table.
Step 7.
Increase the load from 0 to 1000 mA (considering this is a 5 W setup). Record the transmitted power
(from PTx) and received power (from PRx) and add them to GUI FOD tuning table.
New lines can be added using the [+] button on the left.
Figure 86. Filled table with data from different Rx loads
Step 8.
Click the circular button [2] to navigate to second page of the tool.
The initial PRx/PTx power difference (labeled as ∆P) is shown as the green curve. The target of the
tuning is to find compensation values, which should move the blue (compensated ∆P) curve as close to
the 200 mW (orange dashed curve line) as possible. The Qi standard allows a maximum 350 mW
power difference between PRx and PTx. The default target of this tool is set to 200 mW (which can be
adjusted on the right side), The lower value provides a margin that helps prevent false FOD triggering.
Figure 87. FOD tuning with uncompensated/untuned power difference curve
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Step 9.
Move the sliders on right side so that the "After compensation" curve (blue) becomes a relatively flat
line as close to the target ∆P as possible.
Final DCR corresponds to FOD RSER in Rx registers
Final CTC corresponds to FOD CUR THRx in Rx registers
Final OLC corresponds to FOD OFFSETx in Rx registers
The values for [Final CTC [1] – [5]] must each be higher than the previous
Figure 88. Power difference curve after compensation (FOD tuning)
Step 10. Navigate back to the first page of the tool and check compensated ∆P values.
They should be near the given threshold (200 mW in this case).
Figure 89. Compensated ∆P values
Step 11. Copy the compensation value to Rx Registers (Rx FOD Configuration BPP) by clicking the [Write]
button on top of the Rx FOD tuning page.
Step 12. Generate the configuration file to make the changes persistent (navigate to [Rx Registers]>[Rx FOD
Configuration BPP] and use the [Save Rx] button).
Step 13. Load the configuration file to STWLC98.
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Step 14. Repeat previous measurements and check that the results are approximately the same.
The results will not be exactly equal as there are a lot of variables that can influence power difference
(for example, X/Y misalignment, Z gap, transmitter measurement accuracy, etc.).
Step 15. Repeat the test with 5 mm misalignment in the X or Y axis.
In this case, the FOD should not be triggered.
7.5.4
Qi EPP FOD Tuning
Before proceeding, please prepare the Qi compliant EPP power transmitter that can report transmission.
As EPP FOD tuning is very similar to BPP FOD tuning, you can refer to the previous BPP tuning procedure above
for more details.
Step 1.
Set all FOD tuning (RX FOD Configuration EPP) parameters to zero:
Step 1a. place the STWLC98 on the power transmitter and wait for power transfer.
Step 1b. locate the [Rx FOD Configuration EPP] tab and set all parameters to zero
Figure 90. Cleared EPP FOD tuning registers
UM3194 - Rev 1
Step 2.
Generate new configuration file and write to STWLC98.
Step 3.
Open FOD tuning tool by navigation to the [RX FOD Tuning] tab in GUI.
Step 4.
Place the STWLC98 on a Qi-compliant power transmitter.
Step 5.
Connect the electronic load to the STWLC98 output (VOUT) and read received power (value held in
POWER RX register in [Common Registers]>[Mode Monitor]) and output current power (value held in
ICUR register in [Common Registers]>[Mode Monitor]). Write both values to FOD tuning table.
Step 6.
Read the transmitted power value from the Qi-compliant power transmitter and write the values to the
GUI FOD tuning table.
Step 7.
Increase the load from 0 to 1.3 A (considering this is a 15 W setup and 12 V output). Record the
transmitted power (from PTx) and received power from PRx and add the values to the GUI FOD tuning
table.
New lines can be added using the [+] button.
Step 8.
Click the circular [2] button to navigate to the second page of the tool, and switch to EPP on right side.
The tool allows you to set a different target ∆P value for low (0–5 W), medium (5–10 W) and high (10–
15 W) power operation. The procedure is similar to BPP FOD tuning.
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Step 9.
Move the sliders on right to adjust the "After compensation" curve (blue) to achieve relatively flat line as
close to the target ∆P as possible.
Continue with checks and tests as described in BPP FOD tuning.
Step 10. Complete EPP FOD tuning by updating the reference frequency (RX FOD RF register) and reference
quality factor (RX FOD QF register).
Both registers are located in the [Rx configuration Qi] tab in the [Rx register] menu. These two
values are obtained from the Qi EPP transmitter.
7.5.5
UM3194 - Rev 1
Quick method for FOD tuning in STSC
Step 1.
Connect the STEVAL-WLC98RX to your computer and open the GUI. Also prepare the power
transmitter (Tx) and its associated GUI.
This quick method is only valid with STEVAL-WBC2TX50 and STEVAL-WBC2TX70.
An optional step is to disable FOD in Tx (refer to user manual) .This option will not stop calculation of
FOD but Tx will no longer terminate power transfer if the FOD is triggered. The FOD must be enabled
again after tuning has finished.
Step 2.
Center the power receiver coil on the power transmitter coil without any foreign objects (FO), and wait
for power transfer.
Step 3.
In the Tx GUI, there is a parameter called FOD margin. This is a unitless metric for detecting FOD.
The goal of this tuning is get this parameter to approximately 200. Open the [Rx FOD configuration
LIVE] tab. For each current segment, adjust FOD OFFSET to achieve a FOD margin of approximately
200.
The best way to achieve this is to adjust FOD OFFSET on loads that are near the edge of a given
current segment. Then sweep the load across the current segment and check whether the FOD margin
is consistent.
Step 4.
If there is any significant change or nonlinearity in the given current segment, adjust the FOD CUR THR
segment threshold values to obtain a finer division in the relevant load current range.
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
7.6
STSC quick step guide
This guide shows how to obtain maximum power delivery (50 W) using the STWLC98 as the power receiver and
STWBC2 as the power transmitter. Pre-made quick access toolbar buttons can be used to simplify the process.
For detailed information about STSC, packet payloads, and further STSC functionality, please refer to STSC
application note.
The *.bin file containing buttons for the quick access toolbar must be donwnloaded from st.com. To import the file
into the GUI, navigate to the [Step sequencer] button in left side menu and then use the [Load] button and select
the downloaded bin file. The buttons appear on the bottom of the page if import was successful.
Figure 91. Importing quick access toolbar buttons into the GUI
Each button is a set of read/write operations that allow exchanging proprietary packets with the power transmitter
and changing power receiver settings if needed. A response from power transmitter is always required in STSC
and should be checked after each step of the sequence. If a response is not received, or is incorrect, the given
step must be repeated. The receive buffer of the STWLC98 is not cleared automatically, so it is recommended to
clear it after reading data using the [Clear rcvd buffer] button. In real applications, preparing STSC proprietary
packets and evaluating responses shall be done in the host MCU.
The first part of the sequence sets up STSC power transfer. The second part with "STSC xx V" is used to change
power transmitter input USB-PD voltage and power receiver output voltage. It is recommended to change the
voltage gradually to prevent rapid changes and potential risk of overvoltage.
The sequence to obtain maximum power (50 W) with 20 V output voltage is the following:
UM3194 - Rev 1
Step 1.
STSC Authentication–power receiver authentication in power transmitter.
Response: 0x4F 0xAA 0x32 0x66 0x77 0xC6
Step 2.
STSC Request–power receiver request for STSC, power capability 50 W.
Response: 0x1E 0x01 0x1F
Step 3.
STSC 24bits RPP Req (50W)–change of RPP to 24 bit STSC format.
Response: 0x1E 0x01 0x1F
Step 4.
STSC 12 V–request for power transmitter to change USB-PD voltage to 12 V, power receiver output
voltage set to 12 V, FOD parameters updated.
Response: 0x1E 0x01 0x1F
Step 5.
STSC 15 V–request for power transmitter to change USB-PD voltage to 15 V, power receiver output
voltage set to 15 V, FOD parameters updated.
Response: 0x1E 0x01 0x1F
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Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Step 6.
STSC 20 V–request for power transmitter to change USB-PD voltage to 20 V, power receiver output
voltage set to 20 V, FOD parameters updated.
Response: 0x1E 0x01 0x1F
This quick guide updates FOD parameters during STSC voltage modification. Those FOD parameters are only
valid for STEVAL-WLC98RX. In final applications, this must be handled the by host (MCU) and the FOD
parameters must be tuned to final product. For more information about FOD in STSC, refer to FOD tuning section
and FOD tuning guide (application note).
Figure 92. Example of using STSC Authentication button and reading PTx response
Figure 93. Example of using STSC Authentication button and reading PTx response
Note:
UM3194 - Rev 1
Note: Some buttons in the quick access toolbar may contain a wait operation in addition to I²C read/write
operations. This wait operation instructs GUI to wait for set time before proceeding with I²C operations to allow
the STWLC98 sufficient time to complete tasks such as receiving and decoding packets. In a real device, this
will be handled by the host MCU and interrupt-driven operation should be chosen instead of constant wait times.
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7.7
Reference code with STM32 development boards
Description of reference code for uploading patch and configuration compiled in .h file to STWLC98 with STM32.
Please refer to section Configuration file generation for more information about patch, configuration, and .h file
generation.
7.7.1
Hardware requirements
1. STM32 development board (e.g., STM32 Nucleo-144)
2. STEVAL-WLC98RX
7.7.2
Hardware connections
Step 1.
Connect the STWLC98 I²C pins to the master I²C bus.
These signals require pull-up resistors to work properly.
Step 2.
Connect a 5 V power supply to STWLC98 VRECT/VOUT.
Figure 94. Pin connection between host and STWLC98 evaluation board
7.7.3
Software requirements
1. Patch/configuration data in header (.h) file format
2. STWLC NVM programming reference code
3. STM32CubeIDE
7.7.4
Source files
The source files included in the reference code are listed below.
1. stwlc98.h
–
Provides NVM programming API and holds the structure and register definitions of STWLC98.
2. stwlc98.c
–
Main file which describes the NVM related programming sequences and I²C Write/WriteRead
operations.
3. nvm_data.h
–
7.7.5
UM3194 - Rev 1
Patch and configuration data in header file format to be programmed into the chip.
Reference code porting procedure
Step 1.
Create a new project in the STM32CubeIDE with a STM32 development board. Visit the ST website for
STM32CubeIDE documentation.
Step 2.
Copy stwlc98.h, stwlc98.c, and nvm_data.h into the main directory (Core/Src).
Step 3.
Add the following code into Core/Src/main.c.
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UM3194
Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Step 4.
Include the Header file
/* USER CODE BEGIN Includes */
#include "stwlc98.h"
/* USER CODE END Includes */
Step 5.
Define platform functions and variables to be used by the driver API. See below for the function
definitions.
int32_t platform_write(void *phandle, uint8_t *wbuf, int32_t wlen);
int32_t platform_write_read(void *phandle, uint8_t *wbuf, int32_t wlen, uint8_t
*rbuf, int32_t rlen);
void platform_delay(uint32_t millisec);
void *platform_alloc_mem(size_t size);
void platform_free_mem(void *ptr);
Step 6.
Declare and assign the platform functions to mandatory interfaces.
/** stwlcxx is the used part number **/
struct stwlcxx_dev stwlc98 = { 0 };
stwlc98.bus_write = platform_write;
stwlc98.bus_write_read = platform_write_read;
stwlc98.mdelay = HAL_Delay;
stwlc98.alloc_mem = malloc;
stwlc98.free_mem = free;
Step 7.
If user data is needed by the platform functions, initialize the phandle parameter.
struct stmdev_platform platform = {
.hi2c = &hi2c1,
.huart = &huart3,
};
stwlc98.phandle = &platform;
Step 8.
Optionally, initialize log parameters and set log_info to 1 to print more information logs.
```
stwlc98.log = platform_log;
stwlc98.log_info = 1;
```
Note:
When the host controller sends a System Reset command via I²C (FA 20 01 C1 38 01), STWLC98 will respond
with a NACK. The host controller needs to handle the NACK in this case.
7.7.6
API
Table 14. stwlc98_write_fwreg
Name
int32_t stwlc98_write_fwreg(struct stwlc98_dev *dev, uint16_t reg, const uint8_t *data, int32_t len)
Description
Write device firmware register.
Parameters
struct stwlc98_dev *
dev
Pointer to device interface.
uint16_t
reg
Register to write
uint8_t *
data
Pointer to data to write into register
int32_t
len
Number of consecutive bytes to write.
Return Value
int32_t
Error status, return 0 if no error.
Table 15. stwlc98_read_fwreg
UM3194 - Rev 1
Name
int32_t stwlc98_read_fwreg(struct stwlc98_dev *dev, uint16_t reg, uint8_t *data, int32_t len)
Description
Read device firmware register
Parameters
struct stwlc98_dev *
dev
Pointer to device interface.
page 81/94
UM3194
Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
Return Value
uint16_t
reg
Register to read
uint8_t *
data
Pointer to store data read from register
int32_t
len
Number of consecutive bytes to read.
int32_t
Error status, return 0 if no error.
Table 16. stwlc98_get_chip_info
Name
int32_t stwlc98_get_chip_info(struct stwlc98_dev *dev, struct stwlc98_chip_info *info);
Description
Read device information.
Parameters
struct stwlc98_dev *
dev
Pointer to device interface.
struct stwlc98_chip_info *
info
Pointer to device information structure
Return
int32_t
Error status, return 0 if no error.
Table 17. stwlc98_fw_update
Name
int32_t stwlc98_fw_update(struct stwlc98_dev *dev, enum stwlc98_fw_type fw_type, int32_t force_update);
Description
Update STWLC98 patch and config.
Parameters
struct stwlc98_dev *
dev
Pointer to device interface.
enum stwlc98_fw_type
fw_type
Type of firmware data to write
int32_t
force_update
Set 0 if no force update, otherwise yes
Return
7.7.7
int32_t
Error status, return 0 if no error.
Error codes
Table 18. Error codes and descriptions
Error Code
UM3194 - Rev 1
Value
Description
STWLC98_OK
0x00000000U
No error
STWLC98_ERR_BUS_W
0x80000000U
Bus write error
STWLC98_ERR_BUS_WR
0x80000001U
Bus write-read error
STWLC98_ERR_ALLOC_MEM
0x80000002U
Failed to allocate memory
STWLC98_ERR_INVALID_PARAM
0x80000003U
Invalid parameter
STWLC98_ERR_TIMEOUT
0x80000004U
Timeout error
STWLC98_ERR_INVALID_OP_MODE
0x80000005U
Invalid operation mode
STWLC98_ERR_INVALID_CHIP_ID
0x80000006U
Invalid target chip ID
STWLC98_ERR_NVM_ID_MISMATCH
0x80000007U
Compare failed patch or cfg ID
STWLC98_ERR_NVM_DATA_CORRUPTED
0x80000008U
Compare failed patch or cfg data
page 82/94
UM3194
Designing an up to 50 W wireless power receiver based on the STEVAL-WLC98RX evaluation board
7.8
Common testing and debugging issues
Table 19. Common issues and causes
Indication of the issue
Possible causes
•
VRECT voltage too low
•
–
misalignment of the coils too big
–
insufficient transmitter power
RX protection triggered
•
Communication cannot be established
No VOUT voltage
LED D3 blinking
–
–
•
Power transfer terminated
•
•
•
•
Excessive IC temperature
UM3194 - Rev 1
Receiver is not powered
–
–
–
LED D3 off
misalignment
other communication problems (e.g., noise)
misalignment
transmitter not powered
transmitter protection triggered
Charging complete
Foreign object detected
Communication error
High LDO power loss
–
–
LDO drop set too high
Modulation depth too high
page 83/94
UM3194
Qi Certification
8
Qi Certification
STWLC98 is Qi 1.3 EPP compatible and can therefore be Qi certified. The following section describes the basic
requirements necessary for Qi EPP certification.
It should be noted that STWLC98 Extended Power Profile (EPP) Qi compatibility guarantees Baseline Power
Profile (BPP) compatibility as EPP is a BPP extension.
The 6 basic steps of the Qi certification process:
1. The registration procedure starts with the product’s manufacturer filling in an on-line form, providing basic
information about the product, uploading its picture and submitting the necessary self-declaration forms. The
manufacturer then selects an Authorized Test Lab (ATL) which will perform the compliance test, as well as
selecting an Interoperability Testing Center (IOC) which will perform the interoperability test.
2. The Logo License Administrator (LLA) verifies whether the form is filled in correctly.
3. The Authorized Test Lab (ATL) performs the mandatory compliance tests described in the test specification
and releases a test report summary.
4. The Interoperability testing Center (IOC) performs the interoperability test.
5. The product manufacturer finalizes description of the product. Uploads a picture, showing the product as it will
be shipped to customers, and provides a type number identifying the product.
6. The Logo License Administrator (LLA) verifies the information is complete and consistent, after which the
product is made visible in the product registration database.
Figure 95. Qi certification flowchart
For more information regarding the certification procedure, please visit the Wireless Power Consortium website.
UM3194 - Rev 1
page 84/94
UM3194
Board versions
9
Board versions
Table 20. STEVAL-WLC98RX versions
Finished good
STEVAL$WLC98RXA (1)
Schematic diagrams
STEVAL$WLC98RXA schematic diagrams
Bill of materials
STEVAL$WLC98RXA bill of materials
1. This code identifies the STEVAL-WLC98RX evaluation board first version.
UM3194 - Rev 1
page 85/94
UM3194
Regulatory compliance information
10
Regulatory compliance information
Formal Product Notice Required by FCC:
For evaluation only; not FCC approved for resale
FCC NOTICE - This kit is designed to allow:
(1) Product developers to evaluate electronic components, circuitry, or software associated with the kit to
determine
whether to incorporate such items in a finished product and
(2) Software developers to write software applications for use with the end product.
This kit is not a finished product and when assembled may not be resold or otherwise marketed unless all
required FCC equipment authorizations are first obtained. Operation is subject to the condition that this product
not cause harmful interference to licensed radio stations and that this product accept harmful interference. Unless
the assembled kit is designed to operate under part 15, part 18 or part 95 of this chapter, the operator of the kit
must operate under the authority of an FCC license holder or must secure an experimental authorization under
part 5 of this chapter 3.1.2.
Formal Product Notice Required by Industry Canada
For evaluation purposes only. This kit generates, uses, and can radiate radio frequency energy and has not been
tested for compliance with the limits of computing devices pursuant to Industry Canada (IC) rules.
À des fins d'évaluation uniquement. Ce kit génère, utilise et peut émettre de l'énergie radiofréquence et n'a pas
été testé pour sa conformité aux limites des appareils informatiques conformément aux règles d'Industrie Canada
(IC).
Notice for the European Union
The kit STEVAL-WLC98RX is in conformity with the essential requirements of the Directive 2014/53/EU (RED)
and of the Directive 2015/863/EU (RoHS). Applied harmonized standards are listed in the EU Declaration of
Conformity.
Notice for United Kingdom
The kit STEVAL-WLC98RX is in compliance with the UK Radio Equipment Regulations 2017 (UK SI 2017 No.
1206 and amendments) and with the Restriction of the Use of Certain Hazardous Substances in Electrical and
Electronic Equipment Regulations 2012 (UK SI 2012 No. 3032 and amendments). Applied standards are listed in
the UK Declaration of Conformity.
UM3194 - Rev 1
page 86/94
UM3194
Revision history
Table 21. Document revision history
UM3194 - Rev 1
Date
Version
15-Mar-2024
1
Changes
Initial release.
page 87/94
UM3194
Contents
Contents
1
Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
2
Reference design specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3
Overview of the board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4
5
3.1
Test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2
Basic operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3
Functional check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Graphical user interface (GUI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1
Connecting STWLC98 to PC GUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2
Patch and configuration files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3
Configuration file generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.4
Header file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.5
Header file generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.6
Programming the device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.6.1
Using header file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.6.2
Using memh files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Device description and operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
5.1
System block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.2
Integrated power rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.2.1
5.3
5.4
Iload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Internal ADC channel monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.3.1
NTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.3.2
ADCIN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Main LDO regulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.4.1
Regulation loops and protections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.4.2
Dload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.5
UVLO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.6
Chip enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.7
Power up sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.7.1
Vout soft start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.8
LDOs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.9
Protections overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
UM3194 - Rev 1
5.9.1
Two-stage soft overvoltage protection (OVPS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.9.2
Hard overvoltage protection (OVPH). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.9.3
Firmware overvoltage protection (ADC OVP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.9.4
Output overvoltage protection (VOUT OVP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
page 88/94
UM3194
Contents
5.10
5.11
6
5.9.5
Overcurrent protections (OCP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.9.6
Overtemperature protections (OVTP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.9.7
NTC protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
5.9.8
Foreign object detection (FOD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
WPC Qi wireless power transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.10.1
Qi Baseline Power Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.10.2
Qi Extended Power Profile (EPP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.10.3
Wireless power interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Bidirectional communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5.11.1
ASK communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.11.2
FSK communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.11.3
Most common Qi communication packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.11.4
Data transport stream (DTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.12
Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.13
ST Super Charge (STSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.14
Adaptive rectifier configuration (ARC) mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.15
Transmitter (Tx) mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.16
I²C Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.16.1
Data validity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.16.2
Start and stop conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.16.3
Byte format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.16.4
Interface protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.16.5
Writing to a single register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.16.6
Writing to multiple registers with incremental addressing . . . . . . . . . . . . . . . . . . . . . . . . . 46
5.16.7
Reading from a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
5.16.8
Reading from multiple registers with incremental addressing . . . . . . . . . . . . . . . . . . . . . . 47
5.17
GPIOx and INTB pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
5.18
Interrupt registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
STEVAL-WLC98RX description and operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
6.1
Schematic diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
6.2
Bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
6.3
STEVAL-WLC98RX coil description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
6.4
STEVAL-WLC98RX PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
6.5
STWLC98 default configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
6.6
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
UM3194 - Rev 1
6.6.1
Power up waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6.6.2
Efficiency and spatial freedom in the XY plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
page 89/94
UM3194
Contents
7
6.6.3
Spatial freedom in the Z-axis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
6.6.4
Thermal performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Designing an up to 50 W wireless power receiver based on the STEVALWLC98RX evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
7.1
External component design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
7.1.1
Coil selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
7.1.2
Series and parallel resonant capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
7.1.3
VRECT and VOUT capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
7.1.4
ASK modulation capacitor selection and configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
7.1.5
SOVP clamp resistor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
7.1.6
ESD/TVS diodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
7.1.7
NTC thermistor connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
7.2
PCB layout guidelines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
7.3
LDO configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
7.4
External 5V provision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
7.4.1
7.5
Conditions for using external 5V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
FOD tuning guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
7.5.1
RSER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
7.5.2
Power compensation curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
7.5.3
BPP FOD tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
7.5.4
Qi EPP FOD Tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
7.5.5
Quick method for FOD tuning in STSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
7.6
STSC quick step guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
7.7
Reference code with STM32 development boards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
7.8
7.7.1
Hardware requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
7.7.2
Hardware connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
7.7.3
Software requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
7.7.4
Source files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
7.7.5
Reference code porting procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
7.7.6
API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
7.7.7
Error codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Common testing and debugging issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
8
Qi Certification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84
9
Board versions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85
10
Regulatory compliance information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87
UM3194 - Rev 1
page 90/94
UM3194
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Figure 31.
Figure 32.
Figure 33.
Figure 34.
Figure 35.
Figure 36.
Figure 37.
Figure 38.
Figure 39.
Figure 40.
Figure 41.
Figure 42.
Figure 43.
Figure 44.
Figure 45.
Figure 46.
Figure 47.
Figure 48.
Figure 49.
Figure 50.
Figure 51.
Figure 52.
Figure 53.
UM3194 - Rev 1
STEVAL-WLC98RX evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Main board elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Headers and test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
STEVAL-WLC98RX (left) placed on STEVAL-WBC2TX50 (right) transmitter coil . . . . . . . . . . . . . . . . . . . . . . . 6
PC GUI main screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Device selection and connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Save RX button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Configuration ID field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Save folder selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Device selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Confirmation of patch version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Header file save . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Loading the header file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Loading the patch and configuration files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
STWLC98 system block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
PC GUI charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Vout soft start configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Two-stage OVPS Rx protection threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Two-stage OVPS Rx protection settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
HOVP Rx protection threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
HOVP Rx protection settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Hard overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Firmware OVP Rx threshold setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Firmware OVP Rx settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Firmware VOUT OVP Rx threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
ICL Rx selection and threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
OCP Rx protection settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Firmware OCP threshold settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Firmware OCP setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
TSHUT Rx protection threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
TSHUT Rx protection setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Firmware OVTP protection threshold setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Firmware OVTP Rx protection setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Hardware NTC protection (NTC TSHUT) threshold settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Hardware NTC protection (NTC TSHUT) settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Firmware NTC protection threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Firmware NTC protection setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Reading current measured value on NTC pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Qi Baseline Power Profile flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Qi Extended Power Profile flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
HI and LO states in ASK communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Example of a differential bi-phase encoding scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Example of asynchronous serial format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
ASK modulation capacitor connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Example of differential bi-phase encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Example of different response patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
GUI example with header 0x48 and payload 0xA5 0x01 0x77 0xCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Step Sequencer example with header 0x48 and payload 0xA5 0x01 0x77 0xCE . . . . . . . . . . . . . . . . . . . . . . 40
Step Sequencer example MSG SEND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Setting RPP with acknowledgment in GUI (can only be set once, not persistent on reboot) . . . . . . . . . . . . . . . 41
Reading DTS buffer contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Startup waveform with ARC mode at normal Z distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Startup waveform with ARC mode at high Z distance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
page 91/94
UM3194
List of figures
Figure 54.
Figure 55.
Figure 56.
Figure 57.
Figure 58.
Figure 59.
Figure 60.
Figure 61.
Figure 62.
Figure 63.
Figure 64.
Figure 65.
Figure 66.
Figure 67.
Figure 68.
Figure 69.
Figure 70.
Figure 71.
Figure 72.
Figure 73.
Figure 74.
Figure 75.
Figure 76.
Figure 77.
Figure 78.
Figure 79.
Figure 80.
Figure 81.
Figure 82.
Figure 83.
Figure 84.
Figure 85.
Figure 86.
Figure 87.
Figure 88.
Figure 89.
Figure 90.
Figure 91.
Figure 92.
Figure 93.
Figure 94.
Figure 95.
UM3194 - Rev 1
STWLC98 Transmitter mode schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Writing to a single I²C register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Writing to multiple I²C registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Reading from a single I²C register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Reading from multiple I²C registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Interrupt register settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
STEVAL-WLC98RX circuit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Mechanical characteristics of the receiver coil 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Mechanical characteristics of the receiver coil 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Mechanical characteristics of the receiver coil 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
STEVAL-WLC98RX PCB layout top layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
STEVAL-WLC98RX PCB layout inner 1 layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
STEVAL-WLC98RX PCB layout inner 2 layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
STEVAL-WLC98RX PCB layout bottom layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Power up waveforms of a STEVAL-WLC98RX (Rx) and STEVAL-WBC2TX50 (Tx) setup . . . . . . . . . . . . . . . . 59
Efficiency curves for various misalignments in the X-axis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Efficiency curves for various misalignments in the Z-axis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
STWLC98 communication performance at high Z distances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Thermal performance with a 5 W load (5 V/1 A) after 5 minutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Thermal performance with a 15 W load (12 V/1.25 A) after 5 minutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Thermal performance with a 50 W load (20 V/2.5 A) after 5 minutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Rx ASK configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Example of waveform with no output load, COM A enabled, COM B and COM C disabled . . . . . . . . . . . . . . . 66
Example of waveform with 1200 mA output load, COM A and COM B enbaled, COM C disabled . . . . . . . . . . 67
External NTC connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Default LDO configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Default LDO drop curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Recommended interrupts to enable for using external 5 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Recommended protection setting for using external 5 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
FOD offset defined modification of receive power, example diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Cleared BPP FOD tuning registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Rx FOD tuning update table line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Filled table with data from different Rx loads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
FOD tuning with uncompensated/untuned power difference curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Power difference curve after compensation (FOD tuning) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Compensated ∆P values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Cleared EPP FOD tuning registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Importing quick access toolbar buttons into the GUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Example of using STSC Authentication button and reading PTx response . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Example of using STSC Authentication button and reading PTx response . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Pin connection between host and STWLC98 evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Qi certification flowchart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
page 92/94
UM3194
List of tables
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
Target design specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Header and test point descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Description of OCP protection behavior for combinations of all related setting registers. . . . . . . . . . . . . . . . . . . 24
HI and LO state parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
EPT codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Possible separation without and with ARC mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Available functions on GPIO pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Interrupt description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
STEVAL-WLC98RX bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Electrical characteristics of the receiver coil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
STWLC98 default configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Maximum power for Z-axis gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Default STWLC98 ASK configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
stwlc98_write_fwreg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
stwlc98_read_fwreg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
stwlc98_get_chip_info . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
stwlc98_fw_update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Error codes and descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Common issues and causes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
STEVAL-WLC98RX versions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
UM3194 - Rev 1
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UM3194
IMPORTANT NOTICE – READ CAREFULLY
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UM3194 - Rev 1
page 94/94
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