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Voltage Spikes Lead to Deeper Integration

The move by Silicon Labs toward power systems integration on MCUs points to a larger trend followed by Silicon Blue and IMEC, among others.

Efficient voltage regulation is critical to the design of ultra-low powered systems.

I was reminded of this point during a recent interview with Silicon Labs. The company had just announced improvements to both its microcontroller unit (MCU) and wireless MCU for power-sensitive embedded applications. Silicon Labs claimed that their low-power technology enables 40 percent less system current draw and up to 65 percent longer battery life than competing MCU products.

The system that withdraws the least amount of energy from the battery will achieve the lowest power usage – all other conditions being equal. One way to reduce energy usage is by using highly efficient voltage conversion techniques to draw less current – both in steady state and transient or “spiking” scenarios. Improved energy efficiency was a key part of the recent Silicon Labs announcement. But it also lead to an interesting side discussion about energy scavenging systems.

One way to make battery power last longer is through power efficiency. Another is by restoring energy to the battery, e.g., with an alternative energy system. I asked Silicon Labs if their improved MCUs platforms would interface with energy scavengers.

Keith Odland, the company’s  MCU marketing manager, explained that the challenge with interfacing to energy scavenging devices lies with the power inputs. As an example, he cited the use of piezoelectric elements – common in scavenging systems. Even though these devices output micojoules of power, they can still create large voltage spikes in the tens to hundreds order of magnitude.

The voltage regulation techniques that the company has incorporated into their MCUs to improve energy efficiency will also help prepare them to handle future energy scavenging systems. “All of these improvements will … accommodate non-traditional energy sources – things like switching regulators that are boost converters; switching regulators that are buck converters; wide operating ranges; linear regulating systems and temporary energy storage devices.”

Odland did caution that, while intriguing, many energy scavenging devices don’t yet have the economic drivers to push them beyond what is available in most battery platforms. “The exceptions are devices embedded into bridge suspensions and things on top of radio towers that have high servicing costs,” he said. Today, it is still cheaper to replace a $0.15 battery then design a new energy scavenging system.

He noted that the market is beginning to see more creative energy scavenging systems come into main stream, e.g., tire pressure monitoring systems. (see, “Power Bits: Smarter Tires, After CMOS”)

Another alternative power source that is gaining momentum is solar. Here, too, ultra low power is critical to success as was recently demonstrated by the Citizen Watch’s selection of Silicon Blue’s ultra-low power FPGA IP into their solar-powered, Eco-Drive Satellite Wave watch. Citizen claims that this is the world’s first light-powered GPS-synchronized watch.

Regardless of when alternative energy sources like solar and scavengers go main stream, having high efficiency energy conversion capabilities integrated into the same chip as the processor will help designers both now and in the future.

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