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Chip-Scale Atomic Clock

The ultimate in precision--the cesium clock--has been miniaturized

4 min read

The standard by which clocks in the United States are set is a cesium-based atomic clock in Boulder, Colo., that loses less than a nanosecond per day. It’s the size of a small car and draws roughly a kilowatt of power. Less-accurate commercial atomic clocks, which keep time by watching the vibrations of atoms, are typically the size of a suitcase, though not nearly as portable as one. But now, for the first time, atomic clock accuracy is available in a form small enough and power-efficient enough for backpack-size battery-powered devices. Someday an atomic clock might even fit into a smartphone.

Earlier this year, Symmetricom, of San Jose, Calif., introduced the first commercial chip-scale atomic clock, the SA.45s. It measures 4 by 3.5 by 1.1 centimeters, weighs 35 grams, and draws a paltry 115 milliwatts. The tiny clock is accurate to within about less than half a microsecond per day.

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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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