Linear Technology Corporation introduces wireless power transmitters

     Linear Technology Corporation introduces the LTC4125 wireless power transmitter to complement Linear Technology's wireless receiver ics for the wireless charging market. The LTC4125 is a simple, high-performance single-chip full-bridge resonant driver capable of wirelessly delivering up to 5W of power to a companion receiver. In a complete wireless power transmission system consisting of a transmitting circuit, a transmitting coil, a receiving coil and a receiving circuit, the device is used as a transmitting circuit component. The LTC4125 comes in a flat (0.75mm) 20-pin 4mm x 5mm QFN package with underside metal pads for superior thermal performance. Both the Class E and Class I versions of the device are specified to operate in the temperature range ˗40°C to 125°C.

     The LTC4125 wireless power transmitter incorporates three key features that improve the basic transmitter: AutoResonant™, which maximizes the receiver's available power; The optimal power search algorithm to maximize the efficiency of the overall wireless power system; And foreign matter detection to ensure safe and reliable operation when working in an environment where conductive foreign matter is present. The LTC4125 automatically adjusts its drive frequency to match the LC network resonance frequency.

     This AutoResonant switch enables the device to deliver maximum power from low-voltage input power (3V to 5.5V) to fine-tuned receivers, such as Linear Technology's LTC4120 wireless receiver and battery charger, via loosely coupled coils. Wireless power receivers can also be designed using LTC4071 parallel battery chargers or LT3652HV multiple chemical composition battery chargers. To optimize system efficiency, the LTC4125 uses a periodic transmit power search method and adjusts the transmit power based on receiver load requirements. The device stops supplying power in case of failure or when a foreign object is detected.

     The LTC4125's transmit power optimization and foreign object detection capabilities simplify the wireless power system, and these features do not require any direct communication between the transmitter and receiver circuits. The LTC4125 operates over a wide range of transmit-to-receive coil coupling factors without the need for digital communication, avoiding the need for complex signal processing hardware and software to support communication protocols.

     The LTC4125 includes programmable maximum current limits and NTC inputs to provide additional foreign object detection and overload protection. Applications include handheld meters, industrial/military sensors, and similar products for use in harsh environments, portable medical devices, and devices with electrical isolation. The LTC4125-based system provides a robust, self-contained solution that allows transfer distances of up to 10mm and can withstand misalignment resulting in poor coil coupling.