Analog Devices' new MEMS gyro

Recently I’ve noticed an increasing emphasis on reliability in automotive electronics devices and systems. Perhaps I’m simply more aware of the topic, but I prefer to think that engineers are paying more attention to reliability, as they should.

Take Analog Devices Inc. (ADI), for example. This week it launched a third-generation automotive-qualified MEMS (microelectromechanical system) gyroscope that it says is the most stable, vibration-immune automotive-grade gyro available. It attributes the stability to a patented differential quad-beam architecture and a continuous electromechanical self-test feature designed to ensure the integrity of the gyro output signal. ADI says the electromechanical self-test is more reliable than electronic self-test routines.

The gyro, ADXRS800, targets electronic stability control, rollover detection, and pitch detection, all of which can make the driving experience safer as long as the gyro is operating correctly. “A stability control system needs accurate inertial signals at all times, especially when harsh vibrations and shocks are present,” says ADI automotive VP Thomas Wessel. “Safety critical auto applications like this benefit greatly from the ADXRS800’s vibration immunity. The continuous self-test feature is also key to realizing fail-safe system performance according to the highest industry standards.  The innovations that this part delivers will make cars safer.”

ADI’s gyro is likely to benefit from mandates for electronic stability control in the U.S. and elsewhere.

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The ADXRS800 is capable of sensing angular rates up to ±300°/sec while providing high resolution of 80 LSB/°/s on the low end due to its wide dynamic range and low noise of 0.16°/s rms with a 80 Hz filter. Angular rate data is presented as a 16-bit word, as part of a 32-bit serial peripheral interface (SPI) message.

Compared with earlier gyros, the new part offers improved shock and vibration rejection, improved offset stability over temperature, improved sensitivity stability over temperature, and improved noise performance.

Sensitivity to linear acceleration is specified at 0.03 °/sec/g, vibration rectification is 0.0002 °/sec/g², noise-rate density is 0.02°/sec/√Hz at +105°C, and null offset variation is 3°/s maximum over temperature and product life.

Other features include internal temperature compensation over an extended industrial temperature range and an optional ceramic vertical-mount package that enables three-axis sensing on a single PCB without daughter boards. Power consumption is 6 milliamps under typical conditions. The new gyro is available in a cavity plastic SOIC-16 (Z-axis) and a SMT-compatible vertical mount package (X-axis) and is capable of operating across an extended temperature range of -40 °C to 125 °C.

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