As the wireless charging market becomes increasingly more competitive, the technology used only becomes more advanced. Linear Technology’s LTC4120 is an example of that growing complexity. It combines a wireless power receiver with a constant-current/constant-voltage battery charger. The packaged integrated circuit (IC) is meant to function as the receive circuit component in a complete wireless power transfer system comprised of transmit circuitry, transmit coil, receive coil, and receive circuitry.

The LTC4120 accepts a rectified input from 4.2 to 40 V from the receive coil to power a full-featured constant-current/constant-voltage 400-mA battery charger that includes programmable charge current, a programmable 3.5-to-11-V battery float voltage with ±1% accuracy, battery preconditioning with half-hour timeout, bad battery fault detection, negative-temperature-coefficient (NTC) thermal protection, charge status, and a 2-hour safety termination timer.

A 50-to-400-mA charge current can be programmed with a single resistor, with 5% accurate programmable charge current. No additional microprocessor or software is required. It also features dynamic harmonization control (DHC), a patented technique that enables optimal wireless power transfer across a variety of conditions while providing thermal management and overvoltage protection. DHC modulates the resonant frequency of the receiver tank to provide lossless adjustment of the power received as well as the power transmitted, forming an efficient and robust solution for wirelessly charging battery-powered devices.

The receiver also enables battery powered devices to be recharged without previously used, expensive, failure-prone connectors. Products that incorporate the LTC4120 may be contained within sealed enclosures, in moving or rotating equipment, or where cleanliness or sanitation is critical. Various applications include handheld instruments, industrial/military sensors, portable medical devices, and physically small or electrically isolated devices. The LTC4120  is housed in a low-profile (0.75-mm) 16-pin, 3 x 3-mm QFN package with backside metal pad for excellent thermal performance and is guaranteed for operation from -40°C to 125°C, in both E and I grades.