Solar harvester reduces solution size by 50% for wearables

Maxim Integrated Products, Inc. has claimed the smallest solar harvesting solution for space-constrained wearables and internet of things (IoT) applications. These include wearable fitness, medical devices, industrial IoT sensors, asset tracking devices, and wireless sensor networks. The MAX20361 single-/multi-cell solar harvester with maximum power point tracking (MPPT) aims to increase the runtime in these devices by providing a supplemental power source.

(Image: Maxim Integrated) Click for larger image.

A big challenge for battery-operated devices, particularly space-constrained applications like wearables, is that they often have longer battery life requirements, but they can’t fit bigger batteries. This is where energy-harvesting solutions, like solar charging, are being used as an auxiliary power source for these rechargeable batteries.

The fully integrated solution for harvesting energy from single-/multi-cell solar sources includes an ultra-low quiescent current (360nA) boost converter and a charging and protection circuit that is optimized for Li-ion batteries, but it can also be used to charge supercapacitors, thin-film batteries, or traditional capacitors. It also features a programmable charging cut-off voltage with thresholds programmable through an I2C interface as well as a temperature shutoff. The MPPT technique allows efficient harvesting from 15μW to over 300 mW of available input power.

The solar harvester reduces solution size by at least half and increases harvested energy with up to five percent better boost efficiency, compared to the closest competitor, according to Maxim. The adaptive MPPT approach along with the Maxim’s unique integrated harvesting gauge for real-time indications of efficiency also can improve the overall system level efficiency even further, added the company.

Maxim Integrated’s MAX20361 solar harvester simplified block diagram (Image: Maxim Integrated)

“This device offers exciting possibilities for a new supplemental power source to continually charge the battery of a device,” said Frank Dowling, director of the Industrial and Healthcare Business Unit at Maxim Integrated, in a statement. “For example, if you can harvest just 30 mW of solar power per day on a 300 mAHr battery system which typically runs for three weeks, you can as a result extend that runtime by over 50 percent.”

The MAX20361 is available at Maxim Integrated’s website for $2.64 (1000-up, FOB USA). It also is available from authorized distributors. An evaluation kit, the MAX20361EVKIT#, is available for $57.