Electronic Design

Thin Is In At The Embedded Systems Conference, At Least For Energy Cells

Whenever I’m at a conference, I’m frequently asked for my opinion about the “best of show.” Since I know this question is coming, I try to be prepared with a really great product or technology.

At the recent Embedded Systems Conference in San Jose, I thought the best of show was the Thinergy micro energy cell (MEC) from Infinite Power Solutions. At least one engineer I spoke with corroborated this view by volunteering his best of show—the very same Thinergy MEC.

The device is a postage stampsized cell that reminds me of a razor blade. At ESC, Don Tuite and I spoke with Tim Bradow, VP of technical marketing and business development, about the cell. Although the word battery comes to mind when you have a cell that stores energy, Tim told us that the MEC is not a battery in the traditional sense. Batteries degrade over time, he reminded us. This cell does not.

There’s no question that this cell falls into the thin-film category. But Tim stressed his product’s technical superiority over other thin-film battery technologies and thus the unique moniker: micro energy cell. Constructed of metal foil, the cell is flexible and thin enough to be embedded into printed-circuit boards (PCBs), IC packaging, multichip modules (MCMs), and smart cards.

The 4-V cell has 1-mA-hour capacity. Tim calls it the world’s most powerful battery for its size and says it is virtually infinitely rechargeable. IPS specifies 10,000 full-depth of recharges. With shallow discharges, the cell will accept more than 100,000 recharge cycles.

The key spec of the Thinergy cell is that it delivers up to 40 mA of continuous current. This means it can directly power some microprocessors and radio chips. One of these is, of course, the Texas Instruments MSP430, a microcontroller well known for its very low power consumption. IPS and TI have been working together, and we saw a demo product that consisted of the Thinergy cell, a small solar cell, and the TI MSP430 microcontroller and CC2500 RF transmitter.

I want to emphasize that this is not the first appearance of the Thinergy MEC at a trade show. Engineering TV covered the cell at an ESC show last fall. New at this show, though, is a companion chip, a PPMU or passive power-management unit. A conventional power-management unit (PMU) is active, consuming some degree of electrical power all the time. “The ultimate management circuit is one that consumes no overhead,” said Bradow, “and that is precisely what we have invented.”

Since energy harvesting is a prime application area, this PPMU provides a simplified electronic interface between an ambient energy harvester and the Thinergy MEC. The PPMU has no front-end regulation. It charges the MEC “passively” when not in overcharge condition, consuming less than 3 nA of quiescent current. For perpetual power, the system designer need only provide a two-wire input from an energy-harvesting source, such as a solar cell, piezo element, thermal-electric generator, or simple RF harvesting circuit.

The output of the PPMU provides regulated (2.1 to 3.6 V) and unregulated output voltage (approximately 4 V) for direct connection to any ICs. The output current is 30 mA or more, depending on the number of MECs used.

By the way, the Thinergy MECs can be stacked in parallel or run in series by welding cells together. Bradow is quick to interject that this technique is not meant to create a much larger cell, but to add a bit more power if needed.

One of the big ideas that this combo is expected to enable is autonomously powered wireless sensors without capacitors or any other supporting electronics. Bradow says that these sensors will be able to operate for a decade or more.

IPS has conveniently packaged the Thinergy cell and PPMU into a micro power module (MPM). The MPMs are expected to be available for purchase by qualified customers starting in May. Don Tuite’s interview with Tim Braden is part of our video coverage of the Embedded Systems Conference, which can be found on our Web site at electronicdesign.com/subject/esc. If you attended ESC, I’d like to hear what you thought was “best in show.”

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