400mA Wireless Power Receiver & Buck Battery Charger

400mA Wireless Power Receiver & Buck Battery Charger
Overview of the LTC4120
The LTC®4120, a high performance wireless receiver and battery charger, serves as the central component of the receiver electronics
in a wireless battery charging system. The Linear Technology wireless power system is designed to transmit up to 2W to a battery with
a maximum charge current of 400mA. The programmable float voltage of the device accommodates several battery chemistries and
configurations. The LTC4120 was developed with technology partner PowerbyProxi, a field-proven technology company focused on
providing real world wireless power solutions. The IC utilizes PowerbyProxi’s patented dynamic harmonization control (DHC) technique
that enables high efficiency contactless charging with maximum TX to RX coil distance and misalignment without any of the thermal
or overvoltage problems typically associated with wireless power systems. Wireless charging with the LTC4120 enables or improves
many different applications. Unlike consumer-oriented solutions following the Qi standard, the LTC4120-based solution addresses the
needs of high reliability industrial, military & medical applications. For instance, expensive connectors which become failure-prone in
harsh environments can be eliminated. Similarly, wireless charging allows for a completely sealed enclosure for applications that require
sterilization. Elimination of wires enables rechargeable batteries to be placed in moving or rotating equipment. Some applications are simply
too small to use a conventional connector. Wireless charging can also provide transformerless galvanic isolation for high reliability isolated
applications. The LTC4120 provides the ability to charge batteries in applications where it is difficult or impossible to use a connector.
LTC4120 - Key Technical Features
Dynamic Harmonization Control Reduces Alignment Sensitivity and
Extends Power Transmission Range
Enables Up to 2W Wireless Charging at Up to a 1.2cm Gap
Adjustable Battery Float Voltage: 3.5V to 11V
50mA to 400mA Charge Current, Programmed with a Single Resistor
No Microprocessor or Firmware Required
No Transformer Core
Wide Rectified Input Voltage Range: 4.3V to 40V
Thermally Enhanced 16-Lead 3mm × 3mm QFN Package
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Target Applications
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Industrial/Military Sensors and Devices
Portable Medical Devices
Physically Small Devices
Electrically Isolated Devices
Devices for Harsh Environments
LTC4120 Receiver and
Charger Demo Board
The LTC4120 Was Developed with Technology
Partner PowerbyProxi. www.powerbyproxi.com
L, LT, LTC, LTM, Linear Technology and the Linear logo are
registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
Receiver & Buck Battery Charger for Wireless Power Transfer
Wireless Power Transfer (WPT)
An inductive wireless power system consists of transmitter electronics, transmit coil, receive coil and receiver electronics. The
LTC4120-based resonant coupled system uses dynamic harmonization control (DHC) to optimize power transfer and provide
overvoltage protection. This eliminates both the need for precise mechanical alignment between the transmit and receive coils as
well as the need for a coupling core. The LTC4120 wireless buck charger forms the basis for the receiver electronics. The receive
coil can be integrated into the receiver electronics PCB. In collaboration with PowerbyProxi, Linear Technology offers several
different transmitter electronics options. A reference design is available to build a basic transmitter, while several more advanced
transmitters can be purchased from PowerbyProxi, www.powerbyproxi.com. See the LTC4120 product page for more information.
LTC4120 Product Page: http://www.linear.com/product/LTC4120
LTC4120 Application Note: http://www.linear.com/docs/43968
14
COUPLING (TX + RX COIL)
TX CIRCUIT
TX COIL
LTC4120
CIRCUIT
RX COIL
TX
BATTERY
RX
COIL SEPARATION (mm)
DC POWER SUPPLY
1W
12
10
8
2W
6
4
2
WIRELESS BATTERY CHARGING SYSTEM
0
–20 –15 –10 –5
0
5
10 15
COIL CENTER OFFSET (mm)
Wireless Power Transfer System Block Diagram Charging
20
Battery Charge Power
vs RX-TX Coil Location
Proxi-2D
Proxi-Point
Linear Technology Basic and PowerbyProxi Advanced Transmitters
www.linear.com/4120 n 1-800-4-LINEAR
1013A
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