Batteries provide power to many different applications across a wide range of industries. Wireless charging enables those applications where it is difficult or impossible to use a connector. Examples include products that need to operate in harsh environments or need to be cleaned or sterilized, as well as products that are simply too small for a connector. In this video, we will show the LTC(R)4120 400mA wireless power receiver buck battery charger. This device works with a wireless power transmitter to charge a 3.5V to 11V battery with a constant-current/constant-voltage charge algorithm. The LTC4120 was developed with technology partner PowerbyProxi and integrates PowerbyProxi's patented Dynamic Harmonization Control (DHC) technique. This technique enables high-efficiency charging without any of the thermal or overvoltage problems typical of wireless power systems. With the system shown, up to 2 W can be transmitted at a distance of up to 1.2 cm. The LTC4120's adjustable 3.5V to 11V output accommodate several types of batteries, including one-cell and two-cell Li-ion batteries. 50mA to 400mA charge current is programmed with a single resistor. The LTC4120 includes a safety termination timer eliminating the need for a microprocessor.