Tiny, Low-Cost MEMS Gyro IC Sets Performance Records

Oct. 28, 2002
Using the Coriolis effect and its integrated MEMS (iMEMS) surface micromachined process, Analog Devices has produced the smallest, lowest-cost high-performance commercially available angular-rate sensor (gyroscope) with signal-conditioning electronics...

Using the Coriolis effect and its integrated MEMS (iMEMS) surface micromachined process, Analog Devices has produced the smallest, lowest-cost high-performance commercially available angular-rate sensor (gyroscope) with signal-conditioning electronics on the same chip.

Mounted on a small BGA package just 7 by 7 by 3 mm (147 mm3), the ADXRS is much smaller than available gyros, which range in overall size from 15,138 to 159,975 mm3. The Coriolis effect is a phenomenon in which a moving object, subject to a rotation, experiences linear acceleration that's proportional to the rate of rotation.

To make the gyro, an 8-µg polysilicon proof mass is suspended 2 µm over the silicon substrate containing the signal-conditioning electronics. Some 5000 interdigitated fingers, spaced 1.6 µm apart, move in response to the rate of angular rotation, allowing capacitance changes on the order of an incredible 12 zF (1 zeptofarad = 10−21 F) to be measured. The device senses acceleration with 30 µg of resolution and can detect deflection distances of a mere 0.00016 Å. It has a shuttle motion of 3000 g at 15 kHz.

A very important parameter is a high level of rejection for environmental shock and vibration. The gyro can withstand a force of 2000 g. It has a built-in self-test function and can operate over a range of 10,000°/s. It runs on a 5-V supply and draws just 5 mA.

The gyro's ruggedness and low-noise output enable its use in many applications to augment GPS receivers. Applications include triggering automotive airbags during rollovers, improving the accuracy and reliability of GPS systems, and stabilizing moving platforms like autos, airplanes, robots, antennas, and industrial equipment.

"We can offer a roadmap that will provide high-quality and high-performance gyros for as little as $10," says Micromachined Products Division vice president Franklin Weigold.

Two versions will be offered initially: the ADXRS300 with a 300º/s dynamic range, and the ADXRS150 with a 150º/s dynamic range. Pricing is $30 each in 1000-unit lots. Sampling begins this month, with full production by year's end.

Analog Devices Inc., (781) 937-1428; www.analog.com.

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About the Author

Roger Allan

Roger Allan is an electronics journalism veteran, and served as Electronic Design's Executive Editor for 15 of those years. He has covered just about every technology beat from semiconductors, components, packaging and power devices, to communications, test and measurement, automotive electronics, robotics, medical electronics, military electronics, robotics, and industrial electronics. His specialties include MEMS and nanoelectronics technologies. He is a contributor to the McGraw Hill Annual Encyclopedia of Science and Technology. He is also a Life Senior Member of the IEEE and holds a BSEE from New York University's School of Engineering and Science. Roger has worked for major electronics magazines besides Electronic Design, including the IEEE Spectrum, Electronics, EDN, Electronic Products, and the British New Scientist. He also has working experience in the electronics industry as a design engineer in filters, power supplies and control systems.

After his retirement from Electronic Design Magazine, He has been extensively contributing articles for Penton’s Electronic Design, Power Electronics Technology, Energy Efficiency and Technology (EE&T) and Microwaves RF Magazine, covering all of the aforementioned electronics segments as well as energy efficiency, harvesting and related technologies. He has also contributed articles to other electronics technology magazines worldwide.

He is a “jack of all trades and a master in leading-edge technologies” like MEMS, nanolectronics, autonomous vehicles, artificial intelligence, military electronics, biometrics, implantable medical devices, and energy harvesting and related technologies.

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