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EETE JULAUG 2013

Single die MEMS oscillator hits the mainstream By Nick Flaherty Silicon Labs has ported the low temperature MEMs technology it acquired with startup Silicon Clocks in 2010 to Chinese foundry SMIC. This allows a SiGe structure to be built on top of the passivation layer of a CMOS logic chip using the existing CMOS production line and eliminates the drift problems of dual die devices as the materials are specifically chosen to counteract thermal drift. The programmable oscillators run up to 100MHz with frequency stability down to 20ppm and are aimed at cost-sensitive, lowpower and high-volume industrial, embedded and consumer electronics applications such as digital cameras, storage and memory, AT M machines, point-of-sale equipment and multi-function printers. Higher speed devices are planned, says Mike Petrowski, vice president and general manager of Silicon Labs’ timing products. The CMOS MEMs (CMEMS) technology enables guaranteed data sheet performance with 10 years of frequency stability including solder shift, load pulling, VD variation, operating temperature range, vibration and shock. This guaranteed operating life performance is 10 times longer than typically offered by comparable crystal and MEMs oscillators. The oscillators tightly couple the MEMs resonator with CMOS temperature sensor and compensation circuitry, ensuring a highly stable frequency output in the face of thermal transients and over the full industrial temperature range. The end result is a predictable, reliable frequency reference over the long operating lifespans of industrial and embedded applications. The Si50x CMEMS oscillators support any frequency between 32 kHz and 100 MHz. Frequency stability options include ±20, ±30 and ±50 ppm across extended commercial (-20 to 70°C) and industrial (-40 to 85°C) operating temperature ranges. The CMEMS oscillators also offer extensive field- and factory-programmable features including low-power and lowperiod jitter modes, programmable rise/fall times and polarity-configurable outputenable functionality. Using CMOS MEMs rather than a crystal frees customers from supply chain problems that are typical for traditional quartz-based solutions. Because CMEMS oscillators are integrated, monolithic ICs, they are packaged in widely produced, molded-compound 4-pin packages, again ensuring a predictable and reliable supply chain. Printing microbatteries could unravel new designs in medical applications By Julien Happich A team based at harvard university and the University of Illinois at Urbana-Champaign, has demonstrated how 3D printing can now be used to print lithium-ion microbatteries the size of a grain of sand, which could be small enough to fit in tiny devices for medical or communications applications. In recent years engineers have invented many miniaturized devices, including medical implants, flying insect-like robots, and tiny cameras and microphones that fit on a pair of glasses. But often the batteries that power them are as large or larger than the devices themselves, which defeats the purpose of building small. To get around this problem, manufacturers have traditionally deposited thin films of solid materials to build the electrodes. However, due to their ultra-thin design, these solid-state micro-batteries do not pack sufficient energy to power tomorrow’s miniaturized devices. The scientists realized they could pack more energy if they could create stacks of tightly interlaced, ultrathin electrodes that were built out of plane. For this they turned to 3D printing. 3D printers follow instructions from three-dimensional computer drawings, depositing successive layers of material— inks—to build a physical object from the ground up, much like stacking a deck of cards one at a time. The researchers have designed a broad range of functional inks—inks with useful chemical and electrical properties. And they have used those inks with their custom-built 3D printers to create precise structures with the electronic, optical, mechanical, or biologically relevant properties they want. The researchers created an ink for the anode with nanoparticles of one lithium metal oxide compound, and an ink for the cathode from nanoparticles of another. The printer deposited the inks onto the teeth of two gold combs, creating a tightly interlaced stack of anodes and cathodes. The electrodes were then packaged into a tiny container filled with an electrolyte solution. The electrochemical performance is claimed to be comparable to commercial batteries in terms of charge and discharge rate, cycle life and energy densities. The interlaced stack of electrodes, printed layer by layer, create the working anode and cathode of a microbattery - Source and top image: Harvard 12 Electronic Engineering Times Europe July/August 2013 www.electronics-eetimes.com


EETE JULAUG 2013
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