ST STEVAL-ISB68WTX User manual

Introduction
The STEVAL-ISB68WTX evaluation board based on STWLC68JRF designed for wireless power transmitter application.
STWLC68JRF can deliver up to 2.5 W power to a Qi complaint wireless receiver.
Fully integrated STWLC68JRF require few external components for board design and can work with 5-20 V input power supply.
With External USB-to-I2C bridge, the user can monitor and control the STWLC68JRF chip with the STSW-ISB68PRO Graphical
User Interface (GUI).
The STEVAL-ISB68WTX includes several safety mechanisms providing over-temperature, over-current and over-voltage
protection as well as Foreign Object Detection (FOD).
Figure 1. STEVAL-ISB68WTX
Getting started with STEVAL-ISB68WTX for 2.5W TX application
UM2901
User manual
UM2901 - Rev 1 - July 2021
For further information contact your local STMicroelectronics sales office.
www.st.com

1Board Overview
The STEVAL-ISB68WTX evaluation board default configuration is optimized for performance.
The board features:
•STWLC68JRFwireless power transmitter chip with up to 2.5 W output power capability
• Low power applications with 5 V input voltage (supplied externally or USB adapter)
• Very few external components, optimized BOM and PCB space
• On chip high efficiency full bridge inverter
• Embedded ARM Cortex™-M0+ Processor
• Wide input operating range 5 V to 20 V
• 8-channels, 10-bit A/D Converter
• On-chip thermal management and protections (over-voltage, over-current, over-temperature)
• Foreign Object Detection (FOD) supported
• 400 kHz I2C interface for communication with host system (optional)
•External USB-to-I2C converter for interfacing to STWLC68JRF chip
• On-chip thermal management and protections (over-voltage, over-current, over-temperature)
• Foreign Object Detection (FOD) supported
• 400 kHz I2C interface for communication with host system (optional)
• External USB-to-I2C converter for interfacing to STWLC68JRF chip
• Complete kit (board with embedded receiving coil, Graphical User Interface control software)
• Chip-Scale Package (CSP), ROHS Complaint
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Board Overview
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2Board configuration
The configuration settings of the STWLC68JRF chip are retrieved from the OTP memory at power-up, but they
can be temporary changed via GUI once the ISB68WTX is powered and the modified values are kept until a reset
of chip occurs.
The default STWLC68JRF settings are the following:
• The coil and resonant capacitors are designed for delivering 2.5 W using 5 V supply
• The output load to be adjusted gradually in steps of 10 mA to avoid high load transient
• The output current limit is set to 2 A
• The inverter maximum operating frequency set to 205 kHz, minimum operating frequency set to 110 kHz
• The duty cycle range minimum 20%, maximum 50%
• The ping frequency is set to 150Khz, ping interval set to 2seconds
• External TX device monitor feature is enabled
• TX Ping is disabled when external TX is detected
• TX Control Error Packet (CEP) time out set to 800msecs
• Frequency HOP frequency used in case of ASK modulation failure is set to 2900 Hz
• Control Error Packet time out max count set to 6
• Following interrupts are enabled by default
– Over Temperature Protection Interrupt (OTP)
– Over Current Protection Interrupt (OCP)
– End of Power Transfer Packet Interrupt (EPT)
– EXT TX device detect interrupt
• Switch to Qi TX Mode is disabled, need to enable it for starting TX mode
• Enable Tx ping can be used to start the ping (default it is enabled) disable TX ping
• Disable TX ping can be used to stop the Ping (power transfer will be terminated)
• Enable FOD detection (default it is disabled)
• Following Default Protection Threshold settings used
• Over Temperature Protection at 90 °C
• The default setting for the over-temperature protection consists in disabling the TX inverter output in case
one of the temperature sensors detects more than 90 °C
• Over Current Protection (OCP) at 2 A resulting in Tx Inverter output disconnection
• Over Voltage Protection (OVP) at 10 V resulting in Tx inverter output disconnection
2.1 Board configuration and test points
The STEVAL-ISB68WTX has several connectors and test points to ease access to key signals.
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Board configuration
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Figure 2. Description of test points
Figure 3. STEVAL-ISB68WTX layout
2.2 Connection to USB I2C converter board
Connect external USB converter board to P3 connector, please ensure right connections for GND, SDA, SCL
pins , as shown in below picture.
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Connection to USB I2C converter board
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Figure 4. STEVAL-ISB68WTX and USB-I2C converter
2.3 USB to I2C converter board
The USB to I2C bridging dongle is the tool that allows interfacing the receiver to the Graphical User Interface
running on a PC.
Three LEDs monitor the operation of the bridge:
D1 (green) indicates I2C bus activity.
D2 (red) indicates correct initialization of the U1 chip
D3 (yellow) is a power-on indicator.
When the dongle is plugged into the USB port, both D2 and D3 should be on.
Figure 5. USB-to-I2C converter
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USB to I2C converter board
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2.4 Board power supply
The power to the board can be supplied using 5V/2A USB adapter, connected through J1 (microUSB receptacle)
or using external 5V power source.
Ensure a stable supply using high quality cables with minimal DC resistance for best overall efficiency.
2.5 Board configuration
The configuration settings of the STWLC68JRF chip are retrieved from the OTP memory at power-up, but they
can be temporary changed via GUI once the ISB68WTX is powered and the modified values are kept until a reset
of chip occurs.
The default STWLC68JRF settings are the following:
• The coil and resonant capacitors are designed for delivering 2.5 W using 5 V supply
• The output load to be adjusted gradually in steps of 10 mA to avoid high load transient
• The output current limit is set to 2 A
• The inverter maximum operating frequency set to 205 kHz, minimum operating frequency set to 110 kHz
• The duty cycle range minimum 20%, maximum 50%
• The ping frequency is set to 150Khz, ping interval set to 2seconds
• External TX device monitor feature is enabled
• TX Ping is disabled when external TX is detected
• TX Control Error Packet (CEP) time out set to 800msecs
• Frequency HOP frequency used in case of ASK modulation failure is set to 2900 Hz
• Control Error Packet time out max count set to 6
• Following interrupts are enabled by default
– Over Temperature Protection Interrupt (OTP)
– Over Current Protection Interrupt (OCP)
– End of Power Transfer Packet Interrupt (EPT)
– EXT TX device detect interrupt
• Switch to Qi TX Mode is disabled, need to enable it for starting TX mode
• Enable Tx ping can be used to start the ping (default it is enabled) disable TX ping
• Disable TX ping can be used to stop the Ping (power transfer will be terminated)
• Enable FOD detection (default it is disabled)
• Following Default Protection Threshold settings used
• Over Temperature Protection at 90 °C
• The default setting for the over-temperature protection consists in disabling the TX inverter output in case
one of the temperature sensors detects more than 90 °C
• Over Current Protection (OCP) at 2 A resulting in Tx Inverter output disconnection
• Over Voltage Protection (OVP) at 10 V resulting in Tx inverter output disconnection
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Board power supply
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3Functional description
WPC Wireless charging system is shown in the below diagram.
The TX is responsible for controlling the transmitting coil and generating the correct amount
of power requested by the RX.
The RX continuously provides the transmitter with the correct power level requested, by modulating the
transmitter carrier through the controlled resistive or capacitive load. Generating the correct amount of power
ensures the highest level of end to-end efficiency due to reduced energy losses. It also helps maintaining a lower
operational temperature.
The TX can adapt to the amount of energy transferred by the coil by modulating the frequency, duty cycle or
amplitude of the PWM voltage on the transmitting coil.
Figure 6. Functional description
3.1 Power conversion
The power transmitter design uses a full bridge inverter to drive the primary coil and series capacitance. The
power transmitted to the coil is regulated by varying the switching frequency of bridge, higher the operating
frequency (example 200 kHz) for lower power transmission , lower operating frequency (example 110 kHz) for
Higher power transfer.
The coil used in the current design has self-inductance of 6.8 uH, the value of series capacitor 347 nF. The input
voltage to the Full bridge inverter is 5 V.
The LC resonant circuit optimization to be done based on power transfer requirements.
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Functional description
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Figure 7. Power conversation
3.2 Communication and control
The 32-bit core MCU is the supervisor of the whole device and manages all the functional blocks to establish and
maintain communication with the receiver.
Ensure adherence to Qi standard specifications (wherever required), optimize the efficiency by properly adjusting
the operating point and guarantee reliability by monitoring and protecting the device.
3.3 ASK demodulation
Using ASK modulation, the receiver sent Control Error Packets (CEP) to tune operating point for matching load
requirements, the transmitter coil signals are filtered using demodulation filter circuit as shown below and feed in
to VS pin of STWLC68JRF.
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Communication and control
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Figure 8. ASK demodulation circuit
3.4 FOD
STWLC68JRF has FOD detection feature. Any excess power loss in wireless power transfer can be monitored
and the device can stop power transfer.
The FOD detection is enabled by setting TX_FOD_EN bit to 1 in register 0x0021h.
The AUTO FOD detection threshold can be set in AUTO_FOD_THR register 0x00EBh.
FOD is detected when abs(PTX-PRX) > TX_AUTO_FOD_THR * 20mW (20mW unit).
PTX is TX power transferred to RX : Monitor register 0x0070h (2bytes)
PRX is TX Power received by RX : Monitor register 0x0072h (2bytes).
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FOD
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4Component Layout
Figure 9. Component layout
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Component Layout
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5Schematic of STEVAL-ISB68WTX
5.1 Schematic of STEVAL-ISB68WTX
Figure 10. Schematic of STEVAL-ISB68WTX
12
220p
C5
AGND
AC1_COIL AC1
AC2
VS
BOOT2
BOOT1
GND
AGND
12
2u2
C17
12
10u
C13
AGND
V1V8
VOUT
V5V0
BOOT
VRECT
GPIO0 GPIO1
INTB SDA SCL RSTB
SGND
SDA
SCL
INTB
RSTB
VOUT_F
PGND
PGND AGND SGND GND
NTC
V1V8
21
D3
1 2
560R
R5
21
1N4448HLP
D1
12
10u
C14
12
100n
C15
12
10u
C9
12
10u
C10
12
10u
C11
12
100n
C12
12
10n
C18
12
22n
C20
12
680p
C21
12
10n
C19
12
47nC6
12
47nC7
VS
V5V0
V1V8
AC1_COIL
AC2
PCB groundpoint
P4
AC1
1
TP1
V1V8
1
2
3
4
5
6
Header 6
P3
1
2
Header 2
P2
12
4u7
C16
SGND
12
JP3
12
JP2
12
JP1
1 2
5k1
R1
1 2
220k
R2
1 2
10k
R3
1 2
5k1
R4
1 2
4k7
R8
1 2
4k7
R7
1 2
4k7
R6
12
4n7C8
COMM1
D8
CLAMP1
C8
BOOT1
E7
AC1
A6
AC1
B6
AC1
B7
AC1
A7
AC2
A2
AC2
A3
AC2
B2
AC2
B3
BOOT2
C1
CLAMP2
C7
COMM2
D7
VSSP A1
VSSP B1
VSSP A8
VSSP B8
VRECT A4
VRECT A5
VGATE D1
VRECT C3
VRECT B5
VRECT B4
BOOT E8
IEXT C2
VSSA
C5 VSSA
D3 VSSA D4 VSSA D5
VSSA
F6
VSSA
E5 VSSA
F5
VSSA
G6 VSSA G7
VOUT D2
VOUT E1
VOUT E2
VOUT E3
GPIO0 H2 GPIO1 H1 GPIO2 J4 GPIO3 J3 GPIO4 J2 GPIO5 J1
INTB J7
SDA J8
SCL H8
RSTB J6
BOOTSEL J5
DFT
G1
NC
C6
NC
D6
VS
F1
NTC
F8
VOUT F2
VSSD E4 VSSD F3 VSSD F4 VSSD H3 VSSD G2 VSSD G3 VSSD G4
VSSA
C4
VSSD
H4
VSSD
H5
VSSD
H7 VSSD H6
V5V0
E6
V5V0
F7
V1V8 G8
V1V8 G5
STWLC68
U1
SGND
1.5AF1
21
D4
SGND
V5V0
GPIO0 GPIO1
21
SMAJ22A
D5
1 2
180RL1
GND
BLM21SP181BH1
12
100n
C22
HE-RED HE-BLUE
12
100nC2
12
100nC3
VRECT
VOUT
1
2
Header 2
P1
C1 6 C2 3
E1
1
E2
4
B2 5 B1
2
ADC114YUQ
Q1
21
N.M.
D2
1
TP2
1
TP3
1
TP4
1
TP5
1
TP6
1
TP7
1
TP8
VOUT_F
13
2
JP4
VBUS
1
D-
2
D+
3
ID
4
GND
5
Shield
Shell
J1
12
100nC1
12
47nC4
1 2
10k
R9
RSTB
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Schematic of STEVAL-ISB68WTX
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5.2 Schematic of USB-I2C board
Figure 11. Schematic of USB-I2C board
I2C communication
GND
GND
470nF
C4
GND
1M
R1
100nF
C5
GND GND GND
MCP_RSTB
MCP_INTB I/O1
1
GND
2
I/O2
3I/O2 4
VBUS 5
I/O1 6
U3
USBCL6-2
GP0
1
GP1
2
RST
3
URx
4
UTx
5
GP2
6
GP3
7
SDA
8
SCL 9
VUSB 10
D- 11
D+ 12
VSS 13
NC 14 NC 15
VDD 16
U1
MCP2221
RST
VBUS
1
D-
2
D+
3
ID
4
GND
5
Shield
Shell
P1
MicroUSB
VBUS
VDD
VDD
GND
100nF
C1
2.2uF
C3
GND GND
VBUS
1uF
C2
GND
VDD
VIN
1
INHIBIT
3NC 4
VOUT 5
GND
2
U2
LD2981
220R
R7
D1
LED
VDD
D2
LED
220R
R6
D3
LED
470R
R5
GND
VBUS
S1
SW-SPST
100nF
C6
RST
GND
GP2 GP3
GP2 GP3 SDA
SCL
4k7
R2
4k7
R3
VDD VDD
SDA SCL
1
2
3
4
5
6
P2
Header connector
GND
SDA
SCL
MCP_INTB
RSTB
VBUS
4k7
R4
VDDMCP_INTB
D4
STPS1L60ZFY
F1
Littelfuse 0603L025
G
S D 32
1
Q1
FDV303N
GND
RSTB
MCP_RSTB
100k
R8
4k7
R9
VDD
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Schematic of USB-I2C board
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6Bill of material for 2.5 W TX application
Table 1. Bill of material for 2.5W TX
Component Value Manufacturer Part Number Notes
C1, C2, C3, C4 100nF/50V Murata GCM155R71H104KE02D Series resonant capacitor
C4 47nF/50V Murata GCM155R71H473KE02D Series resonant capacitor
C6, C7 47nF/50V Murata GCM155R71H473KE02D Boot strap capacitor
C8 4.7nF/50V Murata GCM155R71H472KE02D Boot strap capacitor
C9, C10, C11, C13, C14 10uF/25V GRM188R61E106MA73D Filtering capacitor
C12, C22, C15 100nF/50V Murata GCM155R71H104KE02D Filtering Capacitors
C16 4.7uF/25V Murata GRM155R61A475MEAAD Filtering Capacitor
C17 1uF/25V Murata GRM155R61E105KA12D Filtering capacitor
C18, C19 10nF/50V Murata GRM155R71H103KA88J Filter capacitor
C20 22nF/50V MLCC, X7R, 50V Filter capacitor
C21 680p/50V MLCC, X7R, 50V Filter capacitor
R1, R4 5K1 1005[0402] Resistor 1%
R2 220K 1005[0402] Resistor 1%
R3 10K 1005[0402] Resistor 1%
R6, R7, R8 4K7 1005[0402] Resistor 1%
D1 1N4448HLP Diode
D2 TVS diode (optional)
D3, D4 LEDs (Optional)
D5 SMAJ22A 22V, TVS Diode
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Bill of material for 2.5 W TX application
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Revision history
Table 2. Document revision history
Date Version Changes
14-Jul-2021 1 Initial release.
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Contents
1Board Overview ...................................................................2
2Board configuration ...............................................................3
2.1 Board configuration and test points................................................3
2.2 Connection to USB I2C converter board............................................4
2.3 USB to I2C converter board ......................................................5
2.4 Board power supply ............................................................6
2.5 Board configuration.............................................................6
3Functional description .............................................................7
3.1 Power conversion ..............................................................7
3.2 Communication and control ......................................................8
3.3 ASK demodulation .............................................................8
3.4 FOD .........................................................................9
4Component Layout ...............................................................10
5Schematic of STEVAL-ISB68WTX .................................................11
5.1 Schematic of STEVAL-ISB68WTX ...............................................11
5.2 Schematic of USB-I2C board....................................................12
6Bill of material for 2.5 W TX application ...........................................13
Revision history .......................................................................14
Contents ..............................................................................15
List of tables ..........................................................................16
List of figures..........................................................................17
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Contents
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List of tables
Table 1. Bill of material for 2.5W TX ............................................................ 13
Table 2. Document revision history ............................................................. 14
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List of tables
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List of figures
Figure 1. STEVAL-ISB68WTX ................................................................1
Figure 2. Description of test points .............................................................4
Figure 3. STEVAL-ISB68WTX layout ...........................................................4
Figure 4. STEVAL-ISB68WTX and USB-I2C converter ...............................................5
Figure 5. USB-to-I2C converter................................................................5
Figure 6. Functional description ...............................................................7
Figure 7. Power conversation.................................................................8
Figure 8. ASK demodulation circuit .............................................................9
Figure 9. Component layout................................................................. 10
Figure 10. Schematic of STEVAL-ISB68WTX...................................................... 11
Figure 11. Schematic of USB-I2C board ......................................................... 12
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List of figures
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