Power Conversion – Wireless Charging

Innovation is a buzzword used often in the technology world. Moore’s Law is being thrown out of the window, and the technology curve is reaching new growth. However, if you have tried to incorporate innovation into the design, you know it can be hard to find the time to do the research and testing required to be truly innovative. Luckily, many partners are producing innovative products that make the design process much easier, and your friends at DigiKey are here to bring you the information you need to find solutions faster.

The field of power conversion has embraced innovation as products develop to become smaller, more efficient, and have better storage capacity. Whether you need solutions that incorporate redundancy, voltage regulation, current alternation, or other thought-provoking conundrums, DigiKey and Analog Devices, Inc. (ADI) have you covered. Let’s review some of the pioneering options ADI offers.

Finding compact, low-power solutions can be a unique problem. ADI has products to assist with that as well. This video showcasing wireless battery chargers for hearing aid and handheld applications features ADI’s LTC4123 and LTC4126 wireless chargers for NiMH and Li-Ion batteries respectively. Both of these devices are ideal for charging hearing aids. Other wireless charger receivers discussed in the video are the LTC4124 and LTC4120 along with a wireless power transmitter, the LTC4125.

The LTC4123 is a low-power wireless receiver or charging NiMH batteries at up to a 25 mA current. The devices to be charged can be in completely sealed enclosures, eliminating the need for any connectors. This device can sense its temperature and pause charging if it gets too hot or cold. The LTC4123 comes in a 2 mm by 2 mm DFN package and requires only four external components for a complete solution. There is a demo board available, the DC2302A, that allows designers to test out the LTC4123 operation to see if it’s right for their application.

The DC2302A demo board for the LTC4123. (Image source: Analog Devices)

The LTC4126 is a low-power Li-Ion battery wireless charger. It has an integrated step-down DC/DC regulator featuring a low-noise multi-mode charge pump powered from the battery, which provides a regulated output of 1.2 V. Charging time is controlled by a 6-hour termination timer, and charge current is fixed at 7.5 mA. The LTC4126 has undervoltage protection and comes in a 2 mm by 2 mm LQFN package requiring a few external components for a complete solution. This device also has a demo board available, the DC2663A-KIT, for evaluation in your application.

The DC2663A-KIT demo board for the LTC4126. (Image source: Analog Devices)

The LTC4124 wireless charger is similar to the LTC4123 but charges Li-Ion batteries and has a pin-selectable charge current up to 100 mA. It has an NTC input, a battery disconnect to prevent over-discharging, and comes in a 2 mm by 2 mm LQFN package. There are a few demo boards available for the LTC4124, including one for 50 mA and one for 100 mA charging.

The DC2770A-A-KIT LTC4124 demo board is set for 50 mA output. Another demo kit, the DC2270A-B, is available for 100 mA output. (Image source: Analog Devices)

The LTC4120 wireless receiver and battery charger can be used for Li-Ion/Polymer batteries (LTC4120-4.2), and because of its programmable float voltage feature, the LTC4120 can accommodate several battery chemistries. The charge current can be set anywhere between 50 mA to 400 mA by using an external resistor. These devices utilize a technique called Dynamic Harmonization Control (DHC) to provide contactless charging across an air gap with high efficiency. The LTC4120 can be used in harsh environments and medical devices. The LTC4120-4.2 has an available evaluation board (DC2181A-A) while the LTC2140 demo board and LTC4125 are paired in their own demo board package (DC2386A-B).

The DC2386A-B demo kit includes an LTC4120 receiver and an LTC44125 transmitter. (Image source: Analog Devices)

The LTC 4125 monolithic wireless power transmitter can deliver 5 W to a properly tuned receiver. This device used AutoResonant switching to automatically adjust the driving frequency to match the resonant frequency of the LC network. The LTC4125 is available in a 4 mm by 5 mm QFN package.

Another aspect of power that ADI has covered is power controllers. Controllers have changed and modernized just as much or more than any power product. A long way from the days when synchronization involved mathematical calculations and manual stabilization, now ADI provides step-down synchronous controllers and the LTC7821 is the newest example. With the LTC7821, an efficiency of 97% is attainable in typical 48 V to 12 V applications while switching at 500 kHz. When compared to traditional devices, this hybrid step-down synchronous converter has better EMI performance and efficiency that can only be matched at one-third the switching frequency. The LTC7821 is available in a 5 mm by 5 mm QFN package. A demo board, the DC2787A, is available to evaluate the LTC7821 for use in your applications.

The DC2787A demo board for evaluating the LTC7821. (Image source: Analog Devices)

With reliability, power requirement adherence, and leading-edge design in mind, Analog Devices and DigiKey have worked hard to give you a suite of solutions at the touch of a button. Analog Devices power management solutions fulfill multiple power needs quickly, efficiently and help you get designs up out to the world that much faster. Fueling the designs of today towards an innovative tomorrow.