Texas-based Silicon Labs is streamlining energy harvesting development for battery-free IoT with a series of energy-efficient wireless SoCs.

The xG22E wireless SoCs are designed to operate within the low-power envelope required for battery-free, energy harvesting applications. The family consists of the BG22E, MG22E and FG22E.

All three should let IoT device makers build high-performance Bluetooth Low Energy, 802.15.4-based or sub-GHz wireless devices for battery-optimised and battery-free applications that can harvest energy from external sources in their environments, such as indoor or outdoor ambient light, ambient radio waves and kinetic motion.

To help device manufacturers build a complete energy harvesting product, Silicon Labs is also announcing a partnership with E-Peas, a provider of power managed ICs (PMICs) for energy harvesting. Silicon Labs and E-Peas (e-peas.com) have co-developed two energy harvesting shields for Silicon Labs’ energy-optimised xG22E explorer kit.

To develop within the tight constraints that energy harvesting requires, the explorer kit lets developers customise the peripherals and debugging options that best match their application and get accurate measurements to build their applications and devices with the energy harvesting shields.

The energy harvesting shields are each tuned and optimised for different energy sources and energy storage technologies. They are custom-fit to slot onto the explorer kit. Notably, one of the shields uses E-Peas’ latest AEM13920 dual-harvester, which allows it to pull energy simultaneously from two distinct energy sources, such as indoor or outdoor light, thermal gradients, and electromagnetic waves without sacrificing on energy conversion efficiency.

The second co-developed shield is based on E-Peas’ AEM00300 shield (e-peas.com/product/aem00300-ambient-energy-manager-battery-charger-pulsed), and is dedicated to harvesting power from random pulsed energy sources.

“As the market for energy harvesting and low-power grows, Silicon Labs remains dedicated to enhancing our wireless MCU and radio stack capabilities to advance the development of battery-free IoT,” said Ross Sabolcik, senior vice president at Silicon Labs (www.silabs.com). “Our efforts to prioritise energy efficiency and increase device longevity underscore our commitment to fostering a more sustainable IoT ecosystem.”

The evolution and widespread deployment of the IoT faces a significant challenge related to powering low-complexity small-form-factor devices. Traditional sources such as mains power or batteries pose scalability and maintenance issues. The emergence of the ambient IoT addresses this by introducing a class of connected devices primarily powered through energy harvesting from ambient sources such as radio waves, light, motion and heat.

Silicon Labs aims to build a device that can address one of the significant difficulties in ambient IoT: creating a platform that can optimise its energy consumption and prolong its lifespan. The xG22E family comes with several features designed to reduce energy use and make it the platform of choice for energy harvesting, including:

• Fast, low-energy cold start for applications starting from a zero-energy state to transmit packets and then rapidly return to sleep. An xG22E device wakes up in 8ms and uses 150µJ, or roughly 0.003% of the energy needed to power a 60W equivalent LED lightbulb for one second.
• Energy conserving deep sleep swift wake-up reduces wake-up energy by 78% compared with other Silicon Labs devices.
• Power-efficient energy mode transition to transition smoothly in and out of energy modes by mitigating current spikes or inrush, which can harm energy storage capacity.
• Multiple deep sleep wake-up options, such as RFSense, GPIO and RTC wake-up sources from the deepest EM4 sleep mode, are suitable for extended storage.

Energy harvesting and conservation technologies offer benefits across industries, including lower energy costs, elimination of battery dependence, and a smaller operational carbon footprint by changing energy consumption sources and reducing battery waste. It also complements many existing IoT applications.

For example, electronic shelf labels are being rapidly adopted by retailers across the globe to allow for more accurate pricing, inventory management and even loss prevention. However, with a single location having as many as thousands of labels, they require a lot of batteries. Fortunately, electronic shelf labels do not need a lot of power, nor do they require always-on connectivity, making them a fit for energy harvesting. By using ambient IoT energy sources, retailers can reduce or eliminate their need for batteries for shelf labels. Other examples in the consumer space include television remote controls that use solar energy and movable, wireless light or appliance switches.