Automotive
Freescale Wireless Charging
Reference Design
for Automotive Applications
Target Applications
• 5 W automotive applications
Designed with automotive in mind
Overview
The 5WTXAUTO reference design is Freescale’s wireless charging solution specifically designed for
automotive applications. From component selection to system operating behavior, every design
decision keeps the complex automotive environment in mind. The result is a highly optimized
automotive system solution with a cost-competitive bill of materials (BOM) and maximum performance.
The design is based on the Wireless Power Consortium (WPC) A13 transmitter definition, comprising
a 12 VDC source voltage, full H-bridge topology and rail voltage control method. The system is able
to operate from an input source of 6–14 VDC, ideal for an automotive environment where the source
voltage can dramatically vary. For example, many vehicles feature a Start/Stop function, turning the
vehicle’s engine off during periods of extended idle. When the vehicle starts back up, the battery
voltage can droop excessively while the starter cranks the engine, creating low operating voltages
for small periods of time. The rail voltage control method is ideal for reducing harmonics emissions,
thereby addressing the necessary EMC requirements for industry. Freescale extends support beyond
WCT-5WTXAUTO Multi-Coil Wireless Charger Block
Block Diagram
WCT-5WTXAUTO Multi-Coil Wireless Charger
Diagram
Proximity Sense
Power Inverter
Buck
Pre-Drive
Inverter Control
Low Power
Optional
Demodulation and
Analog Sensing
Rail Voltage
Control
SPI
CAN
Freescale
CAN PHY
MC33901
WCT100xA
CAN
NFC
Transceiver
GPIO
Freescale Technology
Optional
the specified A13 coil type to allow designers
to choose the coil topology that best meets
their needs.
This reference design uses Freescale’s
innovative wireless charging transmit controller
to perform digital demodulation on incoming
communication from the receiver, thereby
reducing the need for external demodulation
circuitry. Using the wireless charging transmit
controller platform, with its unique DSP
capabilities, allows demodulation to be
performed in software with minimal CPU
overhead. This unique feature provides a
major reduction in BOM costs and the added
benefit of a reduced PCB footprint without
compromising system communications quality.
The transmitter reference design implements a
robust foreign object detection scheme critical
for the safe operation of the charger. Metallic
objects are detected by calculating the power
lost in the system, determining that a certain
power loss threshold is deemed to be due to a
metallic object. For WPC-Qi transmitters, this is
a requirement in the specification.
The reference design showcases the
portfolio’s additional capabilities using
Freescale MWCT1003A wireless charging IC
implementing near field communications (NFC)
functionality. Freescale’s joint partnership with
Melexis Semiconductor demonstrates the
coexistence between wireless charging and
NFC systems. On Freescale’s platform, the
wireless charging system provides a bridge
between the NFC physical interface and the
vehicle network. By co-locating both the
wireless charging and NFC function, control
can remain localized and a higher level of
system integration can be obtained. This
reduces overall system costs while maintaining
implementation flexibility.
Additional features include the ability to enable
CAN, utilizing Freescale’s MC33901 CAN
physical interface controller. As an alternative,
LIN communication can also be established
using the wireless charging transmitter’s SCI
interface. Lastly, the solution features an
alternate low-power standby mode by utilizing
proximity sensing. The hardware contains
sensing electrodes which detect when the user
places the mobile device on the charger. The
Features
Features
Compliant to latest WPC Qi specification
Transfer efficiency greater than 60%
Meets latest FOD requirements
Supports many Qi 5 W coil types
Low active RUN power
Low system standby power
consumption (using Freescale proximity
sense technology)
Rail voltage power control
SPI, UART, I C communication interfaces
2
Benefits
Ensure end solution meets latest industry specification
Maximum energy transfer and lower thermal footprint
Ensures foreign objects are detected and provides safety function
Provides a broad range of magnetics support with a single solution
Increase overall operating efficiency
Lowest standby operating mode
Reduce EMC to meet industry requirements
Communicate to and from wireless charging IC to transfer charging
information (premium only)
Lower system BOM and greater performance
Fast and accurate system calibration, saving time & effort to optimize
system performance
Connect to the vehicle network for control and management
Meets latest automotive requirements
Choose as-is firmware or build value-added features onto
existing library
Supports low-level NFC stack (MWCT1003A only)
On-chip digital demodulation
Run-time calibration
Integrated CAN/LIN support
AEC-Q100 qualified
WCT firmware library
NFC capable
Package Options
Part Number
MWCT1001A
MWCT1003A
Package
64 LQFP
64 LQFP
Available Flash Size
30 KB*
220 KB*
Key Features
Complete controller solution, support most
Qi 5W single coils
Premium controller, I
2
C, UART, SPI, flash
memory for application programming
* Available memory is an estimate only
proximity sensing algorithm uses the wireless
charging transmitter’s GPIOs to detect a device
and wake up the system.
Ultimately, the WCT-5WTXAUTO reference
design is a complete system solution,
containing all of the hardware and software
components necessary to quickly implement a
multicoil charger solution. Freescale provides all
necessary hardware documentation, including
schematics, layout and assembly files as well
as a complete BOM. A firmware library is
provided which contains all of the necessary
wireless charging control blocks. Access to the
library is provided via an API which lets users
interact with parameters and settings contained
in the firmware, providing maximum control to
the engineer. Customers can choose to use a
ready-to-use binary file provided by Freescale
or to take a more developmental approach and
build an application around the firmware library.
Development Tools
WCT-5WTXAUTO
Optimized multicoil 5 W reference design for
automotive applications.
Eclipse™-based CodeWarrior
Development Studio for Microcontrollers
A complete integrated development
environment (IDE) that provides a highly visual
and automated framework to accelerate the
development of the most complex embedded
applications.
WCTGUI
Graphical user interface tool for quickly
configuring and optimizing wireless charging
transmitter solutions.
For more information, visit
freescale.com/WCT-5WTXAUTO
Freescale, the Freescale logo and CodeWarrior are trademarks of Freescale Semiconductor, Inc., Reg. U.S. Pat. & Tm. Off. All other
product or service names are the property of their respective owners. © 2014 Freescale Semiconductor, Inc.
Document Number: WCT5WTXAUTOFS REV 0
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