Digital dual-axis MEMS gyro debuts

PORTLAND, Ore. — Image stabilization algorithms sense the movement of a digital camera, then nudge the camera lens (or sometimes the sensor) to compensate for the movement. As mobile devices integrate higher-resolution cameras, adding relatively inexpensive MEMS gyroscopes is now an option, according to one manufacturer.

Invensense Inc. (Sunnyvale, Calif.) claims to be the first MEMS vendor to offer a digital, two-axis gyroscope chip for camera stabilization. “We have the world's first dual-axis gyro with a digital output,” claimed Steve Nasiri, CEO of Invensense.

Invensense previously claimed to also have developed the world’s smallest analog dual-axis gyro. Since then, other vendors have followed suit. Invensense's digital gyro is a redesigned MEMS chip that consumes 50 percent less power than analog gyros.

A two-axis digital gyroscope chip from Invensense

“With camera phones approaching 8-megapixels, image stabilization is becoming a necessity, and for that you need a two-axis gyro,” said Joseph Jiang, the company's imaging business unit director.

Invensense claims to have lowered costs by using a proprietary eutectic bonding process invented by Nasiri. The process protects the delicate MEMS mechanism from contamination using a CMOS wafer with the gyros digital circuitry used as a cap to create a hermetic seal. The wafer-scale process allows the sealing of thousands of MEMS gyros simultaneously before dicing, thereby shrinking their footprint by stacking dies and lowering costs.

Invensense's previous price goal was just over a $1/axis, but for its new digital MEMS chips it has also lowered its pricing goal. The company also included extra digital circuitry on its chip to ease integration and reduce the overall parts count. Included are automatic gain amplification control, anti-aliasing filters, a temperature sensor and a precision timer to provide uniform timing needed for image stabilization algorithms.

The pitch-and-roll MEMS gyro, called the IDG-2000, measures just 4 x 4 x 0.9 mm, consumes 4 milliamps maximum current and 5 microamps in sleep mode. It also includes an integrated 16-bit A/D converter that communicates over a I2C or SPI serial bus.

The MEMS gyro is being produced on an 8-inch fabrication line rather than a 6-inch line used for analog gyros.

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