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Circuit Could Swap Ultracapacitors for Batteries

MIT engineers are developing a circuit that gets enough out of ultracapacitors to make them usable in medical implants

3 min read

21 June 2010—This week, at the VLSI Circuits Symposium, in Honolulu, a team of engineers from MIT reported that they have invented an energy-storage chip that overcomes one of the last remaining technical hurdles that have kept ultracapacitors from replacing batteries as the energy-storage device of choice for the tiniest electronics.

Ultracapacitors offer several advantages over batteries: High energy density, rapid recharge, and a virtually unlimited number of charge-discharge cycles are but a few. One of the drawbacks of ultracapacitors is that their voltage decreases along with their state of charge; the voltage in a battery remains relatively stable. By the time an ultracapacitor reaches a 25 percent state of charge, its voltage has dropped by half. (The voltage of a lead-acid battery at this state of charge would decrease only by roughly 5 percent.) Because chips usually operate in a fairly narrow voltage range, such a steep drop would cause failures, such as read-write memory errors.

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A Circuit to Boost Battery Life

Digital low-dropout voltage regulators will save time, money, and power

11 min read
Image of a battery held sideways by pliers on each side.
Edmon de Haro

YOU'VE PROBABLY PLAYED hundreds, maybe thousands, of videos on your smartphone. But have you ever thought about what happens when you press “play”?

The instant you touch that little triangle, many things happen at once. In microseconds, idle compute cores on your phone's processor spring to life. As they do so, their voltages and clock frequencies shoot up to ensure that the video decompresses and displays without delay. Meanwhile, other cores, running tasks in the background, throttle down. Charge surges into the active cores' millions of transistors and slows to a trickle in the newly idled ones.

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