It can wirelessly transmit up to 5W of power to the companion receiver.

Linear is wireless charging It announced that it has launched a wireless power transmitter (product name: LTC4125 ) that complements wireless receiver ICs, targeting the market.

The LTC4125 is a simple, high-performance monolithic full-bridge resonant driver capable of wirelessly transmitting up to 5W of power to a comparable companion receiver. It functions as a transmission circuit component in an integrated wireless power transmission system consisting of a transmission circuit, a transmission coil, a reception coil, and a reception circuit.

The LTC4125 wireless power transmitter enhances basic transmitter performance by providing three key features. The first is the AutoResonant™ feature, which maximizes available receiver power. The second is an optimal power search algorithm that maximizes overall wireless power system efficiency. Finally, there is the Foreign Object Detection (FOD) feature, which ensures safe and reliable operation when a conductive external object is present during operation.


The LTC4125 automatically adjusts the driving frequency to match the LC network resonant frequency. Through its AutoResonant switching function, this device can deliver maximum power ranging from low-voltage input power (3V to 5.5V) to battery chargers via coupling coils and tuning receivers, such as Linear’s LTC4120 wireless receiver. The wireless power receiver can also be designed as an LTC4071 shunt battery charger or an LT3652HV multi-chemical battery charger. To optimize system efficiency, the LTC4125 periodically scans for transmission power and adjusts it based on receiver-side load requirements. The device cuts off power supply in the event of fault conditions or the detection of external objects.

Power supply interrupted in the event of an error condition or external object detection

The LTC4125's transmission power optimization and external object detection capabilities, which simplify wireless power systems, eliminate the need for communication between the transmitter and receiver circuits. Without digital communication, the LTC4125 operates across a wide range of coil coupling elements from transmission to reception, eliminating the need for complex signal processing hardware and software capable of supporting communication protocols.

The LTC4125 includes programmable maximum current limiting and NTC inputs as additional means of external object and overload protection. Applications include handheld instruments, industrial/military sensors and similar devices in harsh environments, portable medical devices, and electrically isolated devices. LTC4125-based systems provide a robust and independent solution even under harsh coil coupling conditions caused by mismatches and large transmission distances of up to 10 mm.

The LTC4125 is mounted on a rear metal pad for excellent heat dissipation performance and in a low-profile (0.75mm) 20-pin 4mm x 5mm QFN package. This device is specified for operation from -40°C to 125°C in both E and I classes. It is priced at $4.00 per unit for the E class based on a quantity of 1,000.