Wireless Power Receiver and
400mA Buck Battery Charger
n Dynamic Harmonization Control Optimizes
Wireless Charging Over a Wide Coupling Range
n Wide Input Voltage Range (12.5V to 40V)
n Adjustable Float Voltage (3.5V to 11V)
n Fixed 4.2V Float Voltage Option (LTC4120-4.2)
n 50mA to 400mA Charge Current Programmed with a
n ±1% Feedback Voltage Accuracy
n Programmable 5% Accurate Charge Current
n No Microprocessor Required
n No Transformer Core
n Thermally Enhanced, Low Profile 16-Lead
(3mm × 3mm × 0.75mm) QFN Package
n Handheld Instruments
n Industrial/Military Sensors and Devices
n Harsh Environments
n Portable Medical Devices
n Physically Small Devices
n Electrically Isolated Devices
All registered trademarks and trademarks are the property of their respective owners.
The LTC®4120 is a constant-current/constant-voltage wire-
less receiver and battery charger. An external program-
ming resistor sets the charge current up to 400mA. The
LTC4120-4.2 is suitable for charging Li-Ion/Polymer batter-
ies, while the programmable float voltage of the LTC4120
accommodates several battery chemistries. The LTC4120
uses a Dynamic Harmonization Control (DHC) technique that
allows high efficiency contactless charging across an air gap.
The LTC4120 regulates its input voltage via the DHC pin.
This technique modulates the resonant frequency of a
receiver tank to automatically adjust the power received
as well as the power transmitted to provide an efficient
solution for wirelessly charging battery-powered devices.
Wireless charging with the LTC4120 provides a method
to power devices in harsh environments without requiring
expensive failure-prone connectors. This allows products
to be charged while locked within sealed enclosures, or
in moving or rotating equipment, or where cleanliness or
sanitation is critical.
This full featured battery charger includes accurate RUN
pin threshold, low voltage battery preconditioning and bad
battery fault detection, timer termination, auto-recharge,
and NTC temperature qualified charging. The FAULT pin
provides an indication of bad battery or temperature faults.
Once charging is terminated, the LTC4120 signals end-of-
charge via the CHRG pin, and enters a low current sleep
mode. An auto-restart feature starts a new charging cycle
if the battery voltage drops by 2.2%.
1.01M Li-Ion +
GND PROG FBG
Wireless Rx Voltage/Charge Current vs Spacing
0.8 1.0 1.2 1.4
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