STMicroelectronics STEVAL-WLC38RX User Manual

UM3154
User manual
Getting started with the STEVAL-WLC38RX wireless power receiver evaluation
board for 5 W Qi BPP and 15 W Qi EPP applications
Introduction
The STEVAL-WLC38RX evaluation board is based on STWLC38 and is designed for wireless power receiver applications. It
allows users to quickly start their 5W Qi-BPP and 15W Qi-EPP compatible wireless charging receiver projects.
The STWLC38 wireless power receiver can manage up to 15 W of power according to the Wireless Power Consortium’s
Extended Power Profile (EPP).
The integrated circuit requires only a few external components and offers high design flexibility. Using an on-board USB-to-I2C
bridge, the user can monitor and control the STWLC38 using the STSW-WPSTUDIO graphical user interface (GUI).
STEVAL-WLC38RX includes several safety mechanisms providing overtemperature (OVTP), overcurrent (OCP) and
overvoltage (OVP) protections as well as foreign object detection (FOD) for reliable designs.
Figure 1. STEVAL-WLC38RX evaluation board
UM3154 - Rev 2 - September 2023
For further information contact your local STMicroelectronics sales office.
www.st.com
UM3154
Get started
1
Get started
To get started with STEVAL-WLC38RX, you will need the following items to use the reference design kit:
•
Evaluation kit components:
•
–
STEVAL-WLC38RX board
Additional hardware
–
•
STEVAL-WBC86TX for the best results for a 5 W turnkey wireless charging system or any other Qi
BPP or Qi EPP compliant transmitter available on the market
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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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–
UM3154 - Rev 2
Coil selection guide: AN5961
GUI guide: UM3164
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Reference design specifications
2
Reference design specifications
Target specifications of STEVAL-WLC38RX evaluation board are as follows:
Table 1. reference design specifications
Parameter
Qi compatibility
Qi 1.3 BPP and EPP protocol
Rx application PCB area
24 mm x 34 mm
Rx coil specifications
Inductance 8 uH, 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 / 9 V Extended Power Profile
Output current (Iout, Load)
Recommended current load range is 0.1 – 1 A
Host MCU
STM32 used as a reference, the reference I2C driver can be ported to any other
MCU family
USB-to-I2C converter
Embedded in the evaluation board
Efficiency
Applicable charging gap between Tx
and Rx coils(z-distance)
Misalignment between Tx and Rx coils
(x-y offset from the center)
UM3154 - Rev 2
Description
77.6% (5 W operation) with STEVAL-WBC86TX
81% (peak efficiency) with STEVAL-WBC86TX at 3 W
3 – 13 mm (5 W output) with STEVAL-WBC86TX transmitter,
maximum 16 mm – stable communication without output enabled
12 mm for 5 W output, 18 mm for stable communication without output enabled
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Overview of the Board
3
Overview of the Board
The STEVAL-WLC38RX evaluation board is optimized for performance. The board features:
•
•
•
•
•
•
STWLC38 wireless power receiver chip with BPP and EPP compliant firmware
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
WPC Qi extended power profile (EPP, 15 W) compatible receiver chip
•
•
On board USB-to-I2C converter
USB Type-C® connector for PC GUI connection
Figure 2. Main board elements
•
Series resonant capacitors 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
•
USB/I2C converter–provides a communication channel between a PC and STWLC38. LED D8 (Red)
indicates that the I2C converter is powered, D9 (yellow) indicates that STWLC38 is connected to the GUI.
LED D10 (Green) indicates that I2C communication was initialized and is ready. Switch S1 resets the
converter. Note that header P3 connects the converter’s I2C signals to the STWLC38 I2C signals. Short the
corresponding pins with a jumper to establish a connection between the two ICs.
Red LED (D7)–indicates STWLC38 core power status (LED is on when the core is powered).
•
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Test points
3.1
Test points
STEVAL-WLC38RX 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
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Connector
Name
P1
Rx Coil
P3
I2C
2x4 pin Header: AGND, SDA, SCL, INTB
P6
Control signals
8 pin Header: Programmable GPIOs, ENB, INTB, NTC
P4
VRECT
2-pin Header: VRECT output
P5
VOUT
4-pin Header: VOUT output
P7, P8, P14
GROUND
2-pin Header: Ground connection
Description
4-pin Header: for mounting External RX Coil:
Pin 1,2 AC2; Pin3,4 AC1_COIL
P9, P10
GROUND
4-pin Header: Ground connection
P11
VBUS-VOUT
2 Pin Header: VBUS to VOUT Wire Jumper
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Basic operating modes
3.2
Connector
Name
Description
J1
USB-C
USB-C Connector
Basic operating modes
The receiver generally works in two modes - DC (also called Standalone) mode and AC 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, device shall not be powered from power transmitter (device is put away from power transmitter or
power transmitter is being powered off).
AC 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 (D7). Make sure that Rx is not
powered by external DC power before entering this mode.
3.3
Functional check
Figure 4. Transmitter and receiver boards setup
The first sign of an ongoing power transfer is the D7 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 D7 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 an [ARC mode] feature, which improves spatial
freedom of the charging.
The LED D7 is blinking means some power is transferred, but the amount is insufficient, or the transfer is
unstable. One of the reasons for such instability may be communication issue between the power transmitter and
the power receiver. The instability may as well be caused by one of the protections (OVTP, OCP, OTP) being
triggered.
The built-in USB-I2C converter features three LEDs. LED D8 (RED) indicates presence of power from the USB
connector (J1). LED D9 (YELLOW) indicates that STWLC38 is connected to the GUI. LED D10 (GREEN)
indicates that I2C communication was initialized and is ready.
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Graphical user interface (GUI)
4
Graphical user interface (GUI)
STWLC38 (and other ST wireless charging devices) can be configured using the STCHARGE Wireless Power
Studio GUI (STSW-WPSSTUDIO). 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 STWLC38 to PC GUI
Step 1.
Connect the board to a PC by plugging a USB-C cable into the connector J1.
Make sure the STWLC38 I²C pins are connected to the USB-C connector. This can be done by
shorting the appropriate signals (SDA, SCL, INT) on header P3.
Step 2.
Power on the STWLC38 before connecting to the GUI, this can be done in one of the following ways:
Step 2a. Place it onto a power transmitter. The device operates in Rx mode.
Step 2b. Switch it into DC mode by connecting a DC power supply to the STWLC38 VOUT pin. The
voltage must be no higher than 3 V.
Step 2c. Switch it into DC mode by connecting the STWLC38 vout signal to the VBUS pin of the
converter board.
Note:
Step 3.
Please note that the Rx registers will be available only if the device is operating in Rx mode, DC
mode is mainly used for updating patch and configuration file.
Power up the board and open the GUI on your PC. Click the [Connection] button in the top menu.
Up to two devices can be connected at a time. This allows the user to control both Rx and Tx at the
same time).
Figure 5. PC GUI main screen
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Patch and configuration files
Step 4.
Select [WLC38] as the Rx and click the [Connect] button on the right side of the 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 STWLC38. Updating the firmware is not required but may improve the performance of the
board.
The device can be configured using a Configuration file, a binary file containing settings of all registers which can
be found in the GUI. The GUI can also be used to generate a custom Configuration file, making it easier to quickly
change configuration of the board and/or transfer the configuration to another board.
In GUI, registers are divided into two groups. The value changes of registers colored in RED will take effect only if
a configuration file is generated and written to the device. Changes of registers colored in BLACK will take effect
immediately and can be saved to the configuration file. During power-up, the values of those registers are set to
the values defined in the configuration file written on the device. Registers that cannot be saved to the
configuration file and whose value is lost upon reboot have this fact noted in the description.
4.3
Configuration file generation
Using the STSW-WPSTUDIO makes generating the Configuration file quite simple.
UM3154 - Rev 2
Step 1.
To make sure that the latest values are shown in the GUI, it is recommended to use the [Read
[Rx]WLC38] button to dump values from the device to the GUI. Then, the required changes of the
register may be made. This should be done, especially when going from DC mode to Rx mode.
Step 2.
Click the [Write [RX]WLC38] button to save current configuration to temp memory.
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Configuration file generation
Step 3.
Click the [Save RX] button in the RX Registers tab or the Common registers tab.
Figure 7. Save RX button
Step 4.
Enter a Configuration ID number (used for version control) and press [OK].
Figure 8. Configuration ID field
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Header file
Step 5.
Choose your location for the save file.
After choosing a location, the configuration will be saved as a .memh file in the selected folder.
Figure 9. Save folder selection
4.4
Header file
The GUI can also be used to generate a Header file, a binary .h file containing both Configuration and Patch files.
The Header file makes programming the device using a host MCU easier, as both Configuration and Patch can be
loaded at once 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.
Step 1.
Start by selecting [WLC38] in the top menu.
Figure 10. Device selection
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Header file generation
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
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
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Programming the device
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.
This can be done by shorting the P11 jumper, which connects STWLC38’s VOUT to the USB VBUS. Alternatively,
an external power supply can be used. Voltage of the power supply should be higher than 3 V for this purpose.
The device can be programmed in three ways – by changing the register values directly in the GUI, by using a
Header file, which loads both Configuration and Patch files at once, or by loading the two memh files separately
using the GUI.
Note:
The values written into the registers via the GUI directly are only stored temporarily and will be lost upon chip
reset.
Step 1.
To load the Header file using the GUI, navigate to the Programming tab in the side menu.
Step 2.
Select WLC38 in the top menu and [HEADER] in the toggle selector.
Figure 13. Loading the header file
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 into the device.
Step 5.
To load the memh files (patch and configuration) using the GUI, navigate to the Programming tab in
the side menu.
Note:
UM3154 - Rev 2
STWLC38 has 32 kB of RRAM, which allows for multiple erase/rewrite cycles up to 1000 times.
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Programming the device
Step 6.
Select WLC38 in the top menu and [MEMH] in the toggle selector.
Figure 14. Loading the patch and configuration files
UM3154 - Rev 2
Step 7.
Select the patch and configuration files you want to write.
Step 8.
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. STWLC38 system block diagram
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Integrated power rectifier
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
arranged into an H-bridge, conveniently driven by a control block that monitors the voltage at the AC1 and AC2
pins to optimize the commutations and to charge the external bootstrap capacitors for the high-side switches.
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 designing 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 the ASK communication with the
transmitter.
5.3
Internal ADC channels monitor
The GUI allows to monitor in real-time key parameters by reading the internal ADC channels of the STWLC38
and plotting voltages, current, and temperatures. For further details please refer to the GUI user manual UM3164.
Figure 16. PC GUI charts
5.4
Main LDO regulator
The main LDO regulates the rectified voltage to a target value specified by the user. The output voltage is
configurable in 4 V – 12 V range with a 25 mV step. The default value of output voltage is 5 V for BPP (5W) mode
and 9 V for EPP (15W) mode respectively. However, the target value can be easily changed in the GUI or by an
external host controller.
The main LDO regulator is equipped with two protections:
1.
IVL (input voltage loop): when the Vrect voltage falls under a set threshold, the Vout is temporarily disabled
until the Vrect rises above the threshold again. The default threshold for this protection is 3 V but can be
adjusted in 3.5 V to 10.5 V range with a 0.5 V step.
2.
OCP (overcurrent protection): this protection is triggered when the rectifier current rises above a set
threshold. The threshold can be adjusted to a value between 1.25 A and 1.93 A.
3.
RX UVLO (undervoltage protection): when VRECT falls under a set threshold, the set action may be triggered
as send EPT or permanent disable of VOUT.
4.
UM3154 - Rev 2
Output short circuit protection is realized by a combination of overcurrent protection (OCP) and undervoltage
protection (RX UVLO) mechanisms.
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Chip under voltage lockout
To maintain rectifier stability and ASK communication reliability , it is recommended to provide a certain minimum
load to the rectifier. STWLC38 is equipped with Iload ballast function which draws sufficient current from the
rectifier when the output load current is too small.
The rectifier current consists of the Iload ballast current, the output load current and the IC consumption current.
The Iload ballast current is automatically adjusted to maintain the minimal total load current of the rectifier, as set
in the RX ILOAD BALLAST register.
Naturally when the sum of the output load current and IC consumption exceeds the RX ILOAD BALLAST
threshold value there is no additional current sinked by ILOAD BALLAST block and it is disabled and will be
automatically re-enabled when the total current would drop below the threshold.
5.5
Chip under voltage lockout
STWLC38 is equipped with an under voltage lockout, which triggers when the VAA voltage drops below 2 V,
which results in the device being powered down. Normal operation is resumed as soon as the VAA voltage rises
above 2.1 V.
5.6
Chip enable
The device can be disabled (forced into reset) by pulling the chip enable signal high. When the chip enable signal
is released and left to be pulled down to ground, the device resumes normal operation. If the STWLC38 is in reset
mode, then AC1 and AC2 are connected to GND to protect the device.
5.7
Power up sequence
When the STWLC38 receiver is placed onto a power transmitter, and the patch and configuration files are loaded
into the device, it will initiate communication with the transmitter. After completing all the necessary steps
described in the Qi specification, power transfer is established.
If Patch and/or Configuration files are not loaded, the device will not initialize the communication, therefore power
transfer will not be established. Please refer to Section 4.6 Programming the device for device programming
instructions. The communication will also not be initialized if either the Patch or Configuration or both files are
corrupted.
During the initial phase of the power transfer STWLC38 operates in ARC mode, ST’s proprietary mode, which
makes the power-up sequence smoother and more reliable. For more information, see Section 5.12 Adaptive
rectifier configuration (ARC) mode .
Once the VRECT voltage rises high enough, 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 up after which the firmware loads settings saved in the Cofiguration file saved in NVM. The device is
now ready to operate.
5.8
LDOs
The device is equipped with two internal low drop-out regulators (LDOs) – a 2.5 V and a 1.1 V one, with the later
deriving its power from the former.
The 1.1 V LDO powers the digital part of the IC, while the 2.5 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 shall not exceed 20 mA.
•
•
•
5.9
External LDO capacitors should be placed as close to the IC as possible.
Connect a 1 μF filtering capacitor between the VDD pin and ground.
Connect a 4.7 μF filtering capacitor between the VAA pin and ground.
Protections overview
STEVAL-WLC38RX 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 unexpected operating
conditions – over-voltage and/or over-current. Temperature is monitored as well – the device is equipped with
both internal temperature sensor and pins for external NTC connection.
The majority of software protections can be configured in a GUI and/or by a host controller.
Each software protection can also be configured to disable the device's output and force the receiver to send an
EPT (end power transfer) packet when triggered. If the transmitter receives this packet, it should terminate power
transfer immediately.
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Protections overview
Overvoltage protections (OVP)
•
Ping overvoltage protection (POVP)
–
•
Protects the device against excessive rectifier voltage (VRECT) during the ping phase (first few
milliseconds after the power-up)
–
The threshold is set to 14 V and is released as soon as the rectifier voltage drops below 11 V.
–
Gets disabled after the digital part of the device is powered up (the internal 2.5 V LDO reaches the
target value).
–
When triggered, AC1 and AC2 pins of the device are shorted to ground
–
Cannot be disabled, and the threshold cannot be adjusted
Soft overvoltage protection (SOVP)
–
•
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.
–
Can be disabled in the GUI
–
Can be configured to disable VOUT when triggered
–
Can also be configured to force the receiver to send EPT packet when triggered
Hard overvoltage protection (HOVP)
•
–
Shorts AC1 and AC2 pins to ground when triggered
–
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 6 to 18 V with a 2 V step
Firmware OVP
–
–
–
This protection can be configured to disable VOUT when triggered
The protection can also be configured to force the receiver to send EPT packet when triggered
The threshold of this protection can be set in range of 0 to 18 V
Undervoltage protections (UVLO)
•
Input voltage loop (IVL)
–
•
It monitors the VRECT voltage and automatically reduces the device's output to maintain VRECT at
the set threshold.
–
The threshold can be set from 3 to 10.5 V with a 0.5 V step. The default value is 4 V.
RX UVLO
–
–
–
–
–
It monitors VRECT voltage and disables the device’s output when VRECT drops below a set
threshold.
It can be configured to disable VOUT when VRECT drops below a set threshold.
Can also be configured to force the receiver to send EPT packet when triggered
The threshold can be set from 3 to 10.5 V with a 0.5 V step
Disabled by default
Overcurrent protections (OCP)
•
Hardware OCP
•
–
Monitors the output current
–
Can be configured to disable VOUT when triggered
–
Can also be configured to force the receiver to send EPT packet when triggered
–
The threshold can be set to either 1.25, 1.5, 1.75 or 1.93 A
Firmware OCP
–
–
–
–
Monitors the output current
Can be configured to disable VOUT when triggered
Can also be configured to force the receiver to send EPT packet when triggered
The treshold can be set from 0 to 1.93 A with 1 mA step
Overtemperature protections (OVTP)
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Protections overview
•
Hardware thermal shutdown (TSHUT)
•
–
Can be configured to disable VOUT when triggered
–
The threshold can be set from 105 to 135 °C with a 10 °C step.
Firmware OVTP
•
–
Can be configured to disable VOUT when triggered
–
Can also be configured to force the receiver to send EPT packet when triggered
–
The threshold can be set from 105 to 135 °C with 0.1 °C step.
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 EPT packet when triggered
The threshold can be set from 0 to 2.5 V.
Soft overvoltage protection (SOVP)
SOVP protects the device against excessive rectifier voltage. When VRECT rises above a set threshold, the
device will try to lower its value by connecting external power resistors (connected to IEXT pin) from VRECT to
ground through internal transistors. This approach should achieve lowering 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 to send EPT packet when triggered.
The SOVP can be set to either dynamic or static operation. In dynamic mode , when VRECT > VOUT SET +
SOVP threshold, IEXT switch will be turned-on.
In static mode , when VRECT > 12 V + SOVP threshold, IEXT switch will be turned-on.
The SOVP threshold is programmable from 2 V to 5 V in step sizes of 0.2 V. It can be set by STSW-WPSTUDIO
PC GUI tool or host controller via I2C. SOVP is released when VRECT < SOVP threshold - 1 V.
In dynamic mode, the SOVP threshold is output setting dependent:
•
•
Output enabled: the threshold is set as output voltage + margin
Output disabled: the threshold is set to 12 V + margin
In dynamic mode the user may accidentally trigger protection. As previously mentioned, the threshold is set
relative to the output voltage. When changing the output voltage setting, the SOVP threshold is adjusted
automatically. However, the regulation loop is quite slow and may not be fast enough to accommodate a large
voltage change. This might cause the rectifier voltage to temporarily exceed the SOVP threshold. Therefore, it is
advised to change the output voltage slowly (in multiple smaller steps).
Figure 17. SOVP Rx protection threshold setting
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Protections overview
Figure 18. SOVP Rx protection settings
5.9.2
Hard overvoltage protection (HOVP)
HOVP is the fastest (hardware) over-voltage protection, which prevents the rectifier voltage from rising above a
safe level. The default threshold value is 18 V. Triggering the protection causes STWLC38 to short AC1 and AC2
to ground, effectively shorting the receiving coil. This protection should be used as the last measure, as shorting
the receiving coil will cause a significant rise in the transmitter current. Therefore, the HOVP threshold should be
set higher than any other STWLC38 over-voltage protection (but still lower than AMR listed in the datasheet).
HOVP release value depends on SOVP setting.
•
•
If SOVP is enabled, HOVP is released at SOVP threshold
If SOVP is disabled, HOVP is released at 12 V + SOVP margin (refer to SOVP)
Figure 19. HOVP Rx protection threshold setting
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Protections overview
Figure 20. HOVP Rx protection settings
SOVP enabled, the VRECT voltage oscillates between the HOVP trigger threshold (18 V) and SOVP threshold.
Figure 21. VRECT and OVP thresholds
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Protections overview
5.9.3
Firmware OVP
Firmware OVP is the slowest overvoltage protection. Therefore, it is recommended to set its threshold as the
lowest among the available over-voltage protections. It monitors the rectifier voltage and can be configured to
disable the device’s output and/or force the receiver to send an EPT packet when triggered. The threshold can be
adjusted from 0 to 16 V.
Figure 22. Firmware Rx protection threshold setting
Figure 23. Firmware Rx protection settings
5.9.4
Overcurrent protections (OCP)
The STWLC38 IC is equipped with 2 separate overcurrent protections – one operated by hardware and one
managed by the firmware.
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Protections overview
The hardware OCP causes the set action as send EPT or disable Vout. This protection is triggered by HW. The
threshold can be set to either 1.25, 1.5, 1.75 or 1.93 A.
Figure 24. Over current protection threshold setting
Figure 25. Hardware overcurrent Rx protection selection
The firmware OCP threshold can be adjusted from 0 to 1.75 A. It can also be configured to disable the device’s
output and/or force the receiver to send an EPT packet when triggered.
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Protections overview
Figure 26. Firmware overcurrent Rx protection threshold setting
Figure 27. Firmware overcurrent Rx protection settings
5.9.5
Overtemperature protections (OVTP)
The STWLC38 IC is equipped with one overtemperature protection 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 (10
°C step).
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Protections overview
Figure 28. Hardware overtemperature Rx protection threshold setting
Hardware OVTP can also be configured to disable the device output and/or force the receiver to send an EPT
packet when triggered.
Figure 29. Hardware overtemperature Rx protection settings
The firmware OVTP can be adjusted from 0 °C to 200 °C (with a 0.1 °C step) and can be accessed in the GUI or
by a host controller.
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Protections overview
Figure 30. Firmware overtemperature Rx 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.
Figure 31. Firmware overtemperature Rx protection settings
5.9.6
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 STWLC38 NTC pin. It
is recommended to design the voltage divider to reach the (low) NTC threshold at the highest allowed
temperature.
UM3154 - Rev 2
page 25/81
UM3154
Protections overview
The protection can also be configured to disable the device output and/or force the receiver to send an EPT
packet when triggered.
Figure 32. NTC Rx protection threshold setting
Figure 33. NTC Rx protection settings NTC ADC
5.9.7
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.
UM3154 - Rev 2
page 26/81
UM3154
WPC Qi wireless power transfer
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 indicates the probable presence of a foreign object.
STWLC38 uses precise internal AD converters to perform voltage and current measurements and a 32-bit
arithmetic to keep sufficient accuracy. STWLC38 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.
5.10
WPC Qi wireless power transfer
5.10.1
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 5.9.7 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.
UM3154 - Rev 2
page 27/81
UM3154
WPC Qi wireless power transfer
5.10.2
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 1.2.4.
Figure 34. Qi Baseline Power Profile flowchart
•
•
•
•
UM3154 - Rev 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.
page 28/81
UM3154
Bidirectional communication
5.10.3
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.
Figure 35. Qi Extended Power Profile flowchart
•
•
Negotiation: in this phase the power receiver negotiates with the power transmitter to finetune 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.
Important notes:
•
•
•
5.11
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, instead it should be ramped up smoothly to full power
after power transfer is established.
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.
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.
UM3154 - Rev 2
page 29/81
UM3154
Bidirectional 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 ms.
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 36. HI and LO states in ASK communication
Table 3. 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.
UM3154 - Rev 2
page 30/81
UM3154
Bidirectional communication
Figure 37. 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 38. 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.
STWLC38 uses integrated low resistance N-channel MOSFET transistors to modulate the power signal. The
internal switches are connected to the COMA1, COMB1, COMA2 and COMB2 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 capacitors connection, as well as optional ASK demodulation circuit,
which is required for a transmitter mode operation.
UM3154 - Rev 2
page 31/81
UM3154
Bidirectional communication
Figure 39. ASK modulation capacitor connections
5.11.1.1
5.11.2
ASK communication example: sending a proprietary packet from STWLC38 to STWBC86
The explanation of ASK communication is described in detail in Bi-directional communication application note on
STWLC38 and STWBC86.
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. Please note that a negative polarity results in
a higher induced voltage on the power receiver coil and should therefore be used with care.
The FSK communication is executed via packets. Each packet consists of 3 parts – 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 40. Example of differential bi-phase encoding
UM3154 - Rev 2
page 32/81
UM3154
Bidirectional communication
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.
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) or Not-Defined (ND). ACK is encoded as
a series of 8 ONE bits, NACK is encoded as 8 zero bits and ND is encoded as a series of 8 bit of alternating
ZERO and ONE bits (‘01010101’).
Figure 41. Format of three defined responses
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
•
•
•
•
•
UM3154 - Rev 2
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.
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.
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.
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.
Charge status packet (CSP) contains an unsigned integer which states the current charge status of the
battery in the receiving device. CSP equal to 100 means the battery is fully charged, while CSP equal to 0
means the battery is completely discharged. If the receiving device does not contain a battery or it cannot
provide charge status information, the CSP value should be set to 0xFF.
page 33/81
UM3154
Adaptive rectifier configuration (ARC) mode
•
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 4. EPT codes
5.12
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
Over-temperature, use if (e.g.) the battery temperature exceeds a limit.
EPT/ov
0x04
Over-voltage; use if a voltage exceeds a limit
EPT/oc
0x05
Over-current; 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
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 3
additional millimeters of spatial freedom in the 4 basic spatial directions (up/down/left/right). The ARC mode
function can be configured to be disabled by the firmware after VRECT voltage rises above a set threshold, the
threshold can be configured in the GUI.
The 3 mm improvement is depending on the coils used in Wireless charging system. The result was validated
with the following RX and TX setup.
UM3154 - Rev 2
page 34/81
UM3154
I²C Interface
Figure 42. STEVAL-WBC86TX and STEVAL-WLC38RX setup
The ARC mode is dedicated rectifier setting what allows to increase the spatial freedom of position. The ARC
mode is automatically enabled and the IC stays in ARC mode until the Vrect exceeds the set threshold (RX ARC
THRES). Then the ARC mode is disabled, the rectifier switches to a different operating mode where output can
be enabled.
The table below shows how ARC mode improves ping up spatial freedom.
Table 5. Possible separation without and with ARC mode
5.13
Separation (mm)
Ping without ARC mode
Ping with ARC mode
Centre
OK
OK
4
OK
OK
8
OK
OK
12
OK
OK
16
OK
OK
18
Cannot ping up
OK
19
Cannot ping up
OK
20
Cannot ping up
Cannot ping up
I²C Interface
STWLC38 can operate fully independently i.e., without being interfaced with a host system. In applications in
which the STWLC38 is a part of peripherals managed by the host system, the two SDA and SCL pins could be
connected to the existing I2C bus. The device works as an I2C slave and supports standard (100 kbps), fast (400
kbps). STWLC38 has been assigned 0x61 7-bit hardware address.
UM3154 - Rev 2
page 35/81
UM3154
I²C Interface
The pins are up to 3.3 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.
5.13.1
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.
5.13.2
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.
5.13.3
Byte format
Every byte transferred over the SDA line contains 8 bits. Each byte received by STWLC38 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 bytes reception.
5.13.4
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.
5.13.5
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 STWLC38 through an ACK pulse.
Figure 43. Writing to a single I²C register
UM3154 - Rev 2
page 36/81
UM3154
I²C Interface
5.13.6
Writing to multiple registers with incremental addressing
STWLC38 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 44. Writing to multiple I²C registers
5.13.7
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 STWLC38 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 45. Reading from a single I²C register
5.13.8
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 46. Reading from multiple I²C registers
UM3154 - Rev 2
page 37/81
UM3154
GPIOx and INTB pins
5.14
GPIOx and INTB pins
GPIO0 through GPIO2 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 6. GPIO pins
Code
I/O
Function
0x01
I
Pull-up
0x02
I
Pull-down
0x03
O
Interrupt (Open drain)
0x04
O
Interrupt (Push pull)
0x05
O
FW ready
0x06
I
Disable the main LDO
0x07
I
Disable ASK communication
0x0B
O
Indication of successful Negotation. (Push-pull, active high)
0x0C
O
Indication of successful Negotation. (Push-pull, active low)
0x0D
O
Indication of successful Negotation. (Open drain)
0x29
O
Open drain, active low
0x2A
O
Open drain, active high
0x2B
O
Push-pull, active low
0x2C
O
Push-pull, active high
The INTB pin is an interrupt output line that can be assigned to any internal interrupt condition and used to inform
the host system about a specific event.
5.15
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 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 status tab can be used to determine which interrupt is being triggered at a given moment (read only). The
status bit goes back to zero after the triggering condition is removed.
UM3154 - Rev 2
page 38/81
UM3154
Interrupt registers
Figure 47. Interrupt register settings
UM3154 - Rev 2
page 39/81
UM3154
Schematic diagrams
6
Schematic diagrams
Figure 48. STEVAL-WLC38RX circuit schematic
UM3154 - Rev 2
page 40/81
UM3154
Bill of material (BOM)
7
Bill of material (BOM)
Table 7. STEVAL-WLC38RX BOM
Item Q.ty
UM3154 - Rev 2
Ref.
Value
Description
Manufacturer
Order code
TEST POINT
Harwin
S2751-46R
1
11
TP1, TP2, TP3, TP4, TP5, TP6,
TP7, TP8, TP9, TP10, TP11
2
9
C1, C2, C3, C4, C21, C26, C28,
C30, C31
100n
SMD 0603 CAP
Wurth
885012206095
3
7
R9, R10, R11, R12, R13, R14,
R15
N.M.
SMD 0603 RES
N.M.
N.M.
4
5
C18, C19, C20, C24, C25
10u
SMD 0603 CAP
Murata
GRM188R6YA106MA73D
5
5
JP1, JP2, JP3, JP4, JP5
SMD 0603 JUMPER
N.M.
N.M.
6
5
P4, P7, P8, P11, P14
Header 2
Harwin
M20-9770242
7
5
R19, R20, R23, R24, R25
4k7
SMD 0603 RES
Panasonic
ERJ-3EKF4701V
8
4
C5, C17, C22, C23
N.M.
SMD 0603 CAP
N.M.
N.M.
9
4
C32, C34, C39, C40
100n
SMD 0603 CAP
Wurth
885012206095
10
4
D1, D2
TVS diode
Littelfuse
SMF13A
11
4
C14, C27, C33, C35
SMD 0603 CAP
Murata
GRM188R61E475KE11D
12
3
P5, P9, P10
Header 4
Harwin
M20-9730445
13
5
R3, R7, R18, R30, R31
10k
SMD 0603 RES
Panasonic
ERJ-3GEYJ103V
14
2
R8, R17
100k
SMD 0603 RES
Panasonic
ERJ-3GEYJ104V
15
2
C41, C42
47pF
SMD 0603 CAP
Wurth
885012006055
16
2
C6, C13
3.3n
SMD 0603 CAP
Wurth
885012206086
17
2
C7, C12
47n
SMD 0603 CAP
Wurth
885012206093
18
3
C8, C11, C15
22n
SMD 0603 CAP
Wurth
885012206091
19
2
C9, C10
10n
SMD 0603 CAP
Wurth
885012206089
20
2
C37, C38
390pF
SMD 0603 CAP
Samsung
CL10B391KB8NNNC
21
2
D3, D4
DFN-2
Diodes
1N4448HLP-7
22
2
P2, P13
Header 1
Adam Tech
PH1-01-UA
23
2
R4, R5
200R
SMD 0805 RES
Panasonic
ERJ-P06F2000V
24
2
R27, R28
5k1
SMD 0603 RES
Panasonic
ERJ-3GEYJ512V
25
2
D5, D6
N.M.
TVS diode
N.M.
N.M.
26
2
R35, R36
33R
SMD 0603 RES
Panasonic
ERJ-3GEYJ330V
27
1
C16
1.5n
SMD 0603 CAP
Wurth
885012206084
28
1
RTC
SMD 0603 RES
Vishay
NTCS0603E3104FXT
29
1
C29
1u
SMD 0603 CAP
Wurth
885012206052
30
1
C36
100pF
SMD 0603 CAP
Wurth
885012206077
31
1
D7
LED
Wurth
150060RS75000
32
1
D8
LED
Wurth
150060RS75000
33
1
D9
LED
Wurth
150060YS55040
34
1
D10
LED
Wurth
150060VS55040
35
1
D11
Shottky Diode (1A)
Diodes
B220A-13-F
36
1
J1
USB-C
Wurth
629722000214
4u7
page 41/81
UM3154
Bill of material (BOM)
UM3154 - Rev 2
Item Q.ty
Ref.
37
1
38
Value
Description
Manufacturer
Order code
P1
Header 4
Luxshare
LD81FP008-1H
1
P3
Header 4X2
Harwin
M20-9980445
39
1
P6
Header 8
Harwin
M20-9730845
40
1
R1
6k8
SMD 0603 RES
Panasonic
ERJ-3GEYJ682V
41
1
R2
220k
SMD 0603 RES
Panasonic
ERJ-3GEYJ224V
42
1
R6
N.M.
SMD 0805 RES
N.M.
N.M.
43
1
R16
150k
SMD 0603 RES
Panasonic
ERJ-3GEYJ154V
44
1
R21
820
SMD 0603 RES
Panasonic
ERJ-3GEYJ821V
45
1
R22
47k
SMD 0603 RES
Panasonic
ERJ-U03J473V
46
1
R26
1M
SMD 0603 RES
Panasonic
ERJ-3GEYJ105V
47
1
R32
4k7
SMD 0603 RES
Panasonic
ERJ-3EKF4701V
48
2
R33, R29
N.M.
SMD 0603 RES
N.M.
N.M.
49
1
R34
5k1
SMD 0603 RES
Panasonic
ERJ-3GEYJ512V
50
1
S1
SW-SPST
Bright
P-DT2112C
51
1
U1
STWLC38
STMicroelectronics
STWLC38JRM
52
1
U2
FT260Q
FTDI
FT260Q
53
1
U4
SOT23-6
STMicroelectronics
USBLC6-2SC6
54
1
COIL
Luxshare
LD81FP008-1H
55
4
Standoff
Harwin
R30-6700394
56
4
Screw
Wurth
97790803111
57
1
Pair of wires between COIL and
PCB
CNC Tech
610224
58
1
Glue
Loctite
LOCTITE 454
59
3
2.54 jumper
Wurth
60900213421
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UM3154
STEVAL-WLC38RX description and operation
8
STEVAL-WLC38RX description and operation
8.1
STEVAL-WLC38RX coil description
Table 8. Electrical characteristics of the receiver coil
Parameter
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%)
Figure 49. Mechanical characteristics of the receiver coil 1
UM3154 - Rev 2
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UM3154
STEVAL-WLC38RX coil description
Figure 50. Mechanical characteristics of the receiver coil 2
Figure 51. Mechanical characteristics of the receiver coil 3
UM3154 - Rev 2
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UM3154
STEVAL-WLC38RX PCB layout
8.2
STEVAL-WLC38RX PCB layout
Figure 52. STEVAL-WLC38RX PCB layout top layer
UM3154 - Rev 2
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UM3154
STEVAL-WLC38RX PCB layout
Figure 53. STEVAL-WLC38RX PCB layout inner 1 layer
UM3154 - Rev 2
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UM3154
STEVAL-WLC38RX PCB layout
Figure 54. STEVAL-WLC38RX PCB layout inner 2 layer
UM3154 - Rev 2
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UM3154
STWLC38 default configuration
Figure 55. STEVAL-WLC38RX PCB layout bottom layer
8.3
STWLC38 default configuration
Table 9. STWLC38 default configuration
Parameter
Output voltage (BPP mode, 5 W)
5V
Output voltage (EPP mode, 15 W)
9V
Rectifier mode
Communication capacitors
UM3154 - Rev 2
Value
half-sync up to 160 mA
full-sync above 160 mA
COMA and COMB enabled up to 200 mA Iout
COMB enabled above 200 mA Iout
Input voltage loop (IVL)
4V
Hardware over-current protection (HW OCP)
1.75 A
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UM3154
Typical performance characteristics
Parameter
Value
Software over-current protection (SW OCP)
1.75 A
Soft over-voltage protection (SOVP)
16 V
Software over-temperature protection (SW OVTP)
85 °C
Hardware over-temperature protection (TSHUT)
105 °C
Iload
32 mA
ARC mode disable threshold
6V
Vrect ready threshold (Vout is enabled)
Vout setting + 240 mV
Manufacturer ID
0x0022
I2C address
0x61 (7-bit address)
high-byte first
16bit register address
•
LDO setting (output current dependent)
•
–
Highest LDO drop: 320 mV
–
Lowest LDO drop: 128 mV
Active interrupts
•
–
Message received from TX
–
OCP (over-current) protection
–
RX Output on
–
OVP (over-voltage) protection
–
OVTP (over-temperature) protection
–
Power Transfer Contract to EPP (15W). The Transmitter confirmed the EPP support.
GPIO functions
–
–
8.4
low-byte second
GPIO3 as Interrupt
other GPIOs: no function
Typical performance characteristics
Board specifications as defined before (see Reference design specifications)
Table 10. Typical performance characteristics
Output current [mA]
Output voltage [V]
Rectifier voltage (Vrect) [V]
IC Temperature* [°C]
200
5.00
5.20
34
500
5.00
5.15
38
700
5.00
5.14
41
1000
4.97
5.10
48
*5 minutes at each point, internal thermal sensor, ambient temperature was 23 °C
8.4.1
Power up waveforms
The following figure shows the power up waveforms (receiver side) of a STWLC38 (RX) and STWBC86 (TX)
setup. Transmitter and Receiver coils are aligned; a 500-mA resistive load is connected to the receiver output.
UM3154 - Rev 2
page 49/81
UM3154
Typical performance characteristics
Figure 56. Power up waveforms of a STEVAL-WLC38RX and STEVAL-WBC86TX setup
YELLOW→VRECT, BLUE→VOUT, RED→AC1
8.4.2
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-WLC38RX were measured with STEVAL-WBC86TX 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:
•
•
•
•
•
UM3154 - Rev 2
20 W PISEN wall adapter, model A829-120167C-EU1
USB-C power cable from Vention, model COT
STEVAL-WBC86TX as Transmitter
STEVAL-WLC38RX as Receiver
Electronic load in CC mode, model BK Precision 8500.
page 50/81
UM3154
Typical performance characteristics
Figure 57. Efficiency curves for various misalignments in the X-axis
The data clearly demonstrates how the ARC mode feature improves spatial freedom. However, minimizing coil
misalignment is recommended whenever possible, as a large misalignment leads to lower efficiency of power
transfer. Since FOD is evaluated based on power loss in the system, a large misalignment may also trigger FOD
protection.
8.4.3
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-WLC38RX was also tested at various charging gap distances.
The measurements examined two key performance indicators – efficiency and maximum delivered power.
UM3154 - Rev 2
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UM3154
Typical performance characteristics
Figure 58. Efficiency curves for various misalignments in the Z-axis
Table 11. maximum power for Z-axis gaps
Z gap [mm]
Maximum power(1) [W]
4
5.002
6
5.000
8
5.001
11
5.000
13
5.000
16
3.093
(1) The maximum power is also limited by the transmitter, as STEVAL-WBC86TX is only BPP compatible
ARC mode also improves performance at higher Z-axis distances. The following waveform shows how STWLC38
is able to establish communication even at a high Z-distance (16 mm), and after reaching the default 6 V VRECT
threshold, switches to a different operating mode where output can be enabled.
UM3154 - Rev 2
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UM3154
Typical performance characteristics
Figure 59. STEVAL-WLC38RX communication performance at high Z distances
YELLOW→VRECT, BLUE→VOUT, RED -> AC1
8.4.4
Thermal performance
Figure 60. Thermal performance with a 5 W load (5 V/1 A) after 5 minutes
UM3154 - Rev 2
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UM3154
Typical performance characteristics
Figure 61. Thermal performance with a 15 W load (9 V/1.7 A) after 5 minutes
UM3154 - Rev 2
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UM3154
Designing a 5 W Qi BPP or 15 W Qi EPP wireless power receiver based on STEVAL-WLC38RX evaluation board
9
Designing a 5 W Qi BPP or 15 W Qi EPP wireless power receiver
based on STEVAL-WLC38RX evaluation board
The design should begin with external component selection, as those components 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.
9.1
External component design
STWLC38 requires only a few external components to work properly. The design should begin with coil and series
resonant capacitor selection, as those are the crucial part of the design and affect most of the device’s functions.
9.1.1
Coil selection
Coil selection is a complex problem, as there are several factors which influence the resulting performance. When
selecting the coil, the designer should consider the coil’s inductance, DCR, ACR, current rating, dimensions,
maximum z-distance 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 AN5961.
9.1.2
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).
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.
9.1.3
VRECT and VOUT capacitor selection
VRECT and VOUT capacitor value selection is mostly a tradeoff between load transient response time and
capacitor cost and/or size. A capacitance of 30 uF is recommended for a 15 W application. For lower power
applications, the capacitance on VOUT and VRECT can be reduced depending on power scaling.
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. Please refer to the capacitor datasheet for more
information.
9.1.4
ASK modulation capacitor selection and configuration
STEVAL-WLC38RX features two pairs of modulation capacitors, with each pair having a different capacitance
value – 10 nF for COMA, 22nF for COMB.
UM3154 - Rev 2
page 55/81
UM3154
External component design
The modulation capacitors used in STEVAL-WLC38RX were chosen to ensure good communication performance
under all operating conditions. Using a custom board design may require changing the COMA and COMB
capacitors.
The COMA and COMB 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, four separate capacitor combinations can be selected in total.
Figure 62. Rx ASK configuration
Table 12. Default STWLC38 ASK configuration
Setting
Low Voltage (LV)
Threshold
High Voltage (HV)
Low Current (LC)
Threshold
COMA enabled
COMB enabled
8V
COMA enabled
COMB enabled
Normal Current (NC)
COMA disabled
Low Current to Normal Current:
200 mA
Normal Current to Low Current:
120 mA
COMB enabled
8V
COMA disabled
COMB enabled
The following screenshot shows an example of RX Vrect (yellow), RX COMA (blue), RX COMB (red) and TX
COIL sensing (orange). In the picture you can see how the modulation capacitors affect the Vrect voltage and coil
sense voltage of a coupled transmitter - used for ASK demodulation.
The modulation effect shall be considered in regards to the overall power loss, as the LDO voltage drop (Vrect Vout) multiplied by the output current adds an addition power loss into the system.
Changing the modulation capacitor value may have an impact on the TX coil voltage. This voltage is used for ASK
demodulation circuit. The impact depends on various variables such as coil, gap, voltage, transfered power,
misalignment and another parameters.
UM3154 - Rev 2
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UM3154
External component design
Figure 63. The transition from Low current to Normal current and the effect on modulation
This should be considered when configuring the LDO drop curve (see LDO output voltage configuration).
9.1.5
SOVP clamp resistor selection
SOVP clamp resistors, also known as IEXT resistors, are used as a part of the SOVP protection. When triggered,
STWLC38 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.
9.1.6
ESD/TVS diodes
STEVAL-WLC38 also features two external TVS diodes which protect the STWLC38’s input pins (AC1 and AC2)
against excessive input voltage. The breakdown voltage of those diodes is 14.4 V.
9.1.7
NTC thermistor connection
The figure below shows external NTC connection. Together with the R7 pull-up resistor the NTC forms a voltage
divider, which is connected to the STWLC38 NTC pin. It is recommended to design the voltage divider to reach
the (low) NTC threshold at the highest allowed temperature.
ntc =
ADC raw data two's complement (2 bytes)
acc constant default value 16
ntc calculated value in mV
UM3154 - Rev 2
accumulatedADC
× 2 × 2.25 × 0.8 + 1.8
210 × acc
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UM3154
PCB layout guidelines
Figure 64. External NTC connection
9.2
PCB layout guidelines
•
•
•
•
•
•
•
•
•
9.3
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, and COMBx generate noise. Using shielding near these traces (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, BOOT) to minimize the effects of interference induced from those high di/dt nets.
COMM1, COMM2, BOOT1, 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 ensure ground integrity.
LDO output voltage 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.
UM3154 - Rev 2
page 58/81
UM3154
LDO output voltage configuration
Figure 65. Default LDO configuration
Figure 66. Default LDO drop curve
UM3154 - Rev 2
page 59/81
UM3154
FOD tuning
9.4
FOD tuning
The aim of this tuning is to provide instructions and a step-by-step example of how to fine-tune STWLC38
parameters to comply with Qi requirements regarding foreign object detection.
Note:
9.4.1
In the final product FOD tuning procedure requires a calibrated, Qi-compliant transmitter (like Nok9 system,
GRL, etc.) capable of reporting both the transmitted power and received power (sent back from the receiver
under test) without terminating the power transfer in case a FOD condition is detected.
BPP
Step 1.
Begin by setting all FOD tuning registers to zero and generating a new Configuration file for STWLC38.
Figure 67. Cleared Rx FOD tuning registers
Step 2.
Load the new (cleared) Configuration file into STWLC38.
Step 3.
Open the FOD tuning tool by navigating to the FOD Tuning tab.
Figure 68. FOD Tuning tab
UM3154 - Rev 2
Step 4.
Place STWLC38 onto a Qi-compliant power transmitter.
Step 5.
Connect an electronic load to STWLC38 output (VOUT) and read Prx (RX Received power) and Ptx
(Tx Transmitted power) from the transmitter registers. If the Transmitter is STEVAL-WBC86TX, the
reading of Ptx and Prx is automatically done click on [+] and [Read From RAM]. As transmitter may be
used reference Qi compliant transmitter and then the Prx and Ptx shall be manually written to the table.
page 60/81
UM3154
FOD tuning
Step 6.
Increase the load from 0 to 1000 mA in 100 mA steps (in case of a 5 W setup) and record the Prx and
Ptx values (use the [+] button to add more lines).
The Qi standard allows up to 350 mW difference between Prx and Ptx. The default target of the tool is
set to 200 mW (can be adjusted on the right-hand side). The lower value provides a margin which
helps prevent a false FOD trigger.
Figure 69. Load adjustment
Step 7.
Navigate to the second page of the tool by clicking the 2 button above.
The initial Rx/Tx power difference, labeled ΔP, is shown in green. The target of the tuning is to find
compensation values, which would move the blue (compensated ΔP) curve as close to the 200-mW
(orange dashed) line as possible.
Figure 70. Rx/Tx power difference curve
UM3154 - Rev 2
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UM3154
FOD tuning
Step 8.
Move the sliders on right-hand side to achieve a flat line close the target ΔP.
Figure 71. Tuning to obtain a flat BPP FOD curve
Step 9.
Check the compensated values by navigating back to the first page of the tool.
Figure 72. Compensated values
Step 10. Copy the compensation values located on the right to the Rx Registers (RX BPP FOD Configuration)
and generate a new Configuration file.
Step 11. Load the Configuration file into STWLC38.
Step 12. Repeat the previous measurement under the same conditions and check if the results are the same.
Step 13.
The results will not be exactly the same as there are a lot of variables affecting the power difference
(X/Y missalignment, Z gap, transmitter measurement accuracy, STWLC38 measurement accuracy
etc.), but they should be very similar.
Step 14. Repeat the test with a 5 mm misalignment in the X and Y axis.
FOD should not be triggered by the misalignment.
UM3154 - Rev 2
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UM3154
FOD tuning
9.4.2
EPP
Step 1.
Begin by navigating to the Rx EPP FOD Configuration section.
Step 2.
Set all the registers to 0 and generate a new Configuration file.
Figure 73. Cleared EPP FOD settings
Step 3.
Load the file into the device.
Step 4.
Navigate to the FOD tuning tab, switch to EPP mode and capture the data.
The tool allows the user to set a different target ΔP value for low (0-5 W), medium (5-10 W) and high
(10-15) power operation.
Step 5.
Using reference Qi compliant transmitter the ADC Isns, Prx and Ptx values shall be manually written in
the table.
Figure 74. Tuning to obtain a flat EPP FOD curve
Step 6.
UM3154 - Rev 2
Follow the same procedure as BPP mode to complete the tuning.
page 63/81
UM3154
Reference code with STM32 development boards
Step 7.
The EPP FOD tuning is necessary to adjust the Rf (frequency) and Qf (quality factor). The value used
is from a Qi certified EPP transmitter and should be set to the register shown below:
Figure 75. Rf - Qf
9.5
Reference code with STM32 development boards
9.5.1
Hardware requirements
1.
2.
9.5.2
STM32 development board (e.g., STM32 Nucleo-144)
STEVAL-WLC38RX
Hardware connections
Step 1.
Connect the STWLC38 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 STWLC38 VRECT/VOUT.
Figure 76. Pin connection between host and STWLC38 chip/evaluation board
9.5.3
Software requirements
1.
2.
3.
UM3154 - Rev 2
Patch/Configuration data in header (.h) file format
STWLC NVM programming reference code
STM32CubeIDE
page 64/81
UM3154
Reference code with STM32 development boards
9.5.4
Source files
The source files included in the reference code are listed below.
1.
STWLC38.h
2.
–
Provides NVM programming API and holds the structure and register definitions of STWLC38.
STWLC38.c
Main file which describes the NVM related programming sequences and I2C Write/WriteRead
operations.
nvm_data.h
–
3.
–
9.5.5
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 STWLC38.h, STWLC38.c, and nvm_data.h into the main directory (Core/Src).
Step 3.
Add the following code into Core/Src/main.c.
Step 4.
Include the Header file
/* USER CODE BEGIN Includes */
#include "STWLC38.h"
/* USER CODE END Includes */
Step 5.
Define platform functions and variables to be used by 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 stwlc38 = { 0 };
stwlc38.bus_write = platform_write;
stwlc38.bus_write_read = platform_write_read;
stwlc38.mdelay = HAL_Delay;
stwlc38.alloc_mem = malloc;
stwlc38.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,
};
stwlc38.phandle = &platform;
Step 8.
Optionally, initialize log parameters and set log_info to 1 to print more information logs.
stwlc38.log = platform_log;
stwlc38.log_info = 1;
Step 9.
Execute NVM programming
/* Start FW update */
stwlc38_fw_update(&stwlc38, STWLC38_FW_PATCH_CFG, 0);
UM3154 - Rev 2
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UM3154
Reference code with STM32 development boards
9.5.6
API
9.5.6.1
stwlc38_write_fwreg
Table 13. stwlc38_write_fwreg
Name
int32_t stwlc38_write_fwreg(struct stwlc38_dev *dev, uint16_t reg, const uint8_t *data, int32_t len)
Description
Write device firmware register.
Parameters
Return Value
9.5.6.2
struct stwlc38_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.
int32_t
Error status, return 0 if no error.
stwlc38_read_fwreg
Table 14. stwlc38_read_fwreg
Name
int32_t stwlc38_read_fwreg(struct stwlc38_dev *dev, uint16_t reg, uint8_t *data, int32_t len)
Description
Read device firmware register
Parameters
Return Value
9.5.6.3
struct stwlc38_dev *
dev
Pointer to device interface.
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.
stwlc38_get_chip_info
Table 15. stwlc38_get_chip_info
Name
int32_t stwlc38_get_chip_info(struct stwlc38_dev *dev, struct stwlc38_chip_info *info);
Description
Read device information.
Parameters
Return
9.5.6.4
struct stwlc38_dev *
dev
Pointer to device interface.
struct stwlc38_chip_info *
info
Pointer to device information structure
int32_t
Error status, return 0 if no error.
stwlc38_fw_update
Table 16. stwlc38_fw_update
Name
int32_t stwlc38_fw_update(struct stwlc38_dev *dev, enum stwlc38_fw_type fw_type, int32_t force_update);
Description
Update STWLC38 patch and config.
Parameters
UM3154 - Rev 2
struct stwlc38_dev *
dev
Pointer to device interface.
enum stwlc38_fw_type
fw_type
Type of firmware data to write
int32_t
force_update
Set 0 if no force update, otherwise yes
page 66/81
UM3154
Common testing and debugging issues
9.5.7
Error codes
Table 17. Error codes and descriptions
9.6
Error code
Value
Description
STWLC38_OK
0x00000000U
No error
STWLC38_ERR_BUS_W
0x80000000U
Bus write error
STWLC38_ERR_BUS_WR
0x80000001U
Bus write-read error
STWLC38_ERR_ALLOC_MEM
0x80000002U
Failed to allocate memory
STWLC38_ERR_INVALID_PARAM
0x80000003U
Invalid parameter
STWLC38_ERR_TIMEOUT
0x80000004U
Timeout error
STWLC38_ERR_INVALID_OP_MODE
0x80000005U
Invalid operation mode
STWLC38_ERR_INVALID_CHIP_ID
0x80000006U
Invalid target chip ID
STWLC38_ERR_NVM_ID_MISMATCH
0x80000007U
Compare failed patch or cfg ID
STWLC38_ERR_NVM_DATA_CORRUPTED
0x80000008U
Compare failed patch or cfg data
Common testing and debugging issues
Table 18. 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 D7 blinking
–
–
•
Power transfer terminated
•
•
•
•
Excessive IC temperature
UM3154 - Rev 2
Receiver is not powered
–
–
–
LED D7 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 67/81
UM3154
Board versions
10
Board versions
Table 19. STEVAL-WLC38RX versions
Finished good
STEVAL$WLC38RXA (1)
Schematic diagrams
STEVAL$WLC38RXA schematic diagrams
Bill of materials
STEVAL$WLC38RXA bill of materials
1. This code identifies the STEVAL-WLC38RX evaluation board first version.
UM3154 - Rev 2
page 68/81
UM3154
Qi Certification
11
Qi Certification
STWLC38 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 STWLC38 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 77. Qi certification flowchart
For more information regarding the certification procedure, please visit the Wireless Power Consortium website.
UM3154 - Rev 2
page 69/81
UM3154
Regulatory compliance information
12
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-WLC38RX 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 the United Kingdom
The kit STEVAL-WLC38RX 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.
UM3154 - Rev 2
page 70/81
UM3154
Appendix
13
Appendix
Thermal measurements on the Board tested at 25⁰C ambient temperature.
Note:
The ambient temperature should not exceed 65⁰C.
Figure 78. Temperature Before Power Transfer Maximum 25⁰C on STEVAL-WBC86TX
UM3154 - Rev 2
page 71/81
UM3154
Appendix
Figure 79. Maximum Temperature of the Board after 2hours (40.8⁰C) – 5W power transfer STEVALWLC38RX
Figure 80. Maximum Temperature of the Board after 2hours (42.5⁰C) – 5W power transfer
UM3154 - Rev 2
page 72/81
UM3154
Appendix
Figure 81. Maximum Temperature of the Board and Plastic case after 2hours (33.5⁰C) – 5W power transfer
UM3154 - Rev 2
page 73/81
UM3154
Revision history
Table 20. Document revision history
UM3154 - Rev 2
Date
Version
17-Jul-2023
1
27-Sep-2023
2
Changes
Initial release.
Updated Section 6 Schematic diagrams, Section 7 Bill of material (BOM).
Minor text changes.
page 74/81
UM3154
Contents
Contents
1
Get 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 STWLC38 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
Device description and operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
5.1
System block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.2
Integrated power rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.3
Internal ADC channels monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.4
Main LDO regulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.5
Chip under voltage lockout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.6
Chip enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.7
Power up sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.8
LDOs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.9
Protections overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.10
5.9.1
Soft overvoltage protection (SOVP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.9.2
Hard overvoltage protection (HOVP). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.9.3
Firmware OVP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.9.4
Overcurrent protections (OCP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.9.5
Overtemperature protections (OVTP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.9.6
NTC protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.9.7
Foreign object detection (FOD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
WPC Qi wireless power transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.10.1
Wireless power interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.10.2
Qi Baseline Power Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
5.10.3
Qi Extended Power Profile (EPP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5.11
Bidirectional communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
UM3154 - Rev 2
page 75/81
UM3154
Contents
5.11.1
ASK communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.11.2
FSK communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.11.3
Most common Qi communication packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5.12
Adaptive rectifier configuration (ARC) mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.13
I²C Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.13.1
Data validity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.13.2
Start and stop conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.13.3
Byte format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.13.4
Interface protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.13.5
Writing to a single register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.13.6
Writing to multiple registers with incremental addressing . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.13.7
Reading from a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.13.8
Reading from multiple registers with incremental addressing . . . . . . . . . . . . . . . . . . . . . . 37
5.14
GPIOx and INTB pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.15
Interrupt registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
6
Schematic diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
7
Bill of material (BOM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
8
STEVAL-WLC38RX description and operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
9
8.1
STEVAL-WLC38RX coil description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8.2
STEVAL-WLC38RX PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.3
STWLC38 default configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
8.4
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.4.1
Power up waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.4.2
Efficiency and spatial freedom in the XY plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
8.4.3
Spatial freedom in the Z-axis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
8.4.4
Thermal performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Designing a 5 W Qi BPP or 15 W Qi EPP wireless power receiver based on
STEVAL-WLC38RX evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
9.1
9.2
UM3154 - Rev 2
External component design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
9.1.1
Coil selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
9.1.2
Series and parallel resonant capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
9.1.3
VRECT and VOUT capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
9.1.4
ASK modulation capacitor selection and configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
9.1.5
SOVP clamp resistor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
9.1.6
ESD/TVS diodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
9.1.7
NTC thermistor connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
PCB layout guidelines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
page 76/81
UM3154
Contents
9.3
LDO output voltage configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
9.4
FOD tuning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
9.5
9.6
9.4.1
BPP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
9.4.2
EPP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Reference code with STM32 development boards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
9.5.1
Hardware requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
9.5.2
Hardware connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
9.5.3
Software requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
9.5.4
Source files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.5.5
Reference code porting procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.5.6
API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
9.5.7
Error codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Common testing and debugging issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
10
Board versions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
11
Qi Certification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
12
Regulatory compliance information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
13
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74
UM3154 - Rev 2
page 77/81
UM3154
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.
reference design specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
header and test point descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
HI and LO state parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
EPT codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Possible separation without and with ARC mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
GPIO pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
STEVAL-WLC38RX BOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Electrical characteristics of the receiver coil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
STWLC38 default configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
maximum power for Z-axis gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Default STWLC38 ASK configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
stwlc38_write_fwreg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
stwlc38_read_fwreg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
stwlc38_get_chip_info . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
stwlc38_fw_update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Error codes and descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Common issues and causes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
STEVAL-WLC38RX versions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
UM3154 - Rev 2
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UM3154
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.
UM3154 - Rev 2
STEVAL-WLC38RX evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Main board elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Headers and test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Transmitter and receiver boards setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Confirmation of patch version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Header file save . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Loading the header file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Loading the patch and configuration files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
STWLC38 system block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
PC GUI charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
SOVP Rx protection threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
SOVP Rx protection settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
HOVP Rx protection threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
HOVP Rx protection settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
VRECT and OVP thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Firmware Rx protection threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Firmware Rx protection settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Over current protection threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Hardware overcurrent Rx protection selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Firmware overcurrent Rx protection threshold setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Firmware overcurrent Rx protection settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Hardware overtemperature Rx protection threshold setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Hardware overtemperature Rx protection settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Firmware overtemperature Rx protection threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Firmware overtemperature Rx protection settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
NTC Rx protection threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
NTC Rx protection settings NTC ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Qi Baseline Power Profile flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Qi Extended Power Profile flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
HI and LO states in ASK communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Example of a differential bi-phase encoding scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Example of asynchronous serial format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
ASK modulation capacitor connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Example of differential bi-phase encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Format of three defined responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
STEVAL-WBC86TX and STEVAL-WLC38RX setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Writing to a single I²C register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Writing to multiple I²C registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Reading from a single I²C register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Reading from multiple I²C registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Interrupt register settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
STEVAL-WLC38RX circuit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Mechanical characteristics of the receiver coil 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Mechanical characteristics of the receiver coil 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Mechanical characteristics of the receiver coil 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
STEVAL-WLC38RX PCB layout top layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
STEVAL-WLC38RX PCB layout inner 1 layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
page 79/81
UM3154
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.
UM3154 - Rev 2
STEVAL-WLC38RX PCB layout inner 2 layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
STEVAL-WLC38RX PCB layout bottom layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Power up waveforms of a STEVAL-WLC38RX and STEVAL-WBC86TX setup . . . . . . . . . . . . . . . . . . . . . . . 50
Efficiency curves for various misalignments in the X-axis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Efficiency curves for various misalignments in the Z-axis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
STEVAL-WLC38RX communication performance at high Z distances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Thermal performance with a 5 W load (5 V/1 A) after 5 minutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Thermal performance with a 15 W load (9 V/1.7 A) after 5 minutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Rx ASK configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
The transition from Low current to Normal current and the effect on modulation . . . . . . . . . . . . . . . . . . . . . . 57
External NTC connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Default LDO configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Default LDO drop curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Cleared Rx FOD tuning registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
FOD Tuning tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Load adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Rx/Tx power difference curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Tuning to obtain a flat BPP FOD curve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Compensated values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Cleared EPP FOD settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Tuning to obtain a flat EPP FOD curve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Rf - Qf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Pin connection between host and STWLC38 chip/evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Qi certification flowchart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Temperature Before Power Transfer Maximum 25⁰C on STEVAL-WBC86TX . . . . . . . . . . . . . . . . . . . . . . . . 71
Maximum Temperature of the Board after 2hours (40.8⁰C) – 5W power transfer STEVAL-WLC38RX . . . . . . . . 72
Maximum Temperature of the Board after 2hours (42.5⁰C) – 5W power transfer . . . . . . . . . . . . . . . . . . . . . . 72
Maximum Temperature of the Board and Plastic case after 2hours (33.5⁰C) – 5W power transfer . . . . . . . . . . 73
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UM3154
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UM3154 - Rev 2
page 81/81
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