MEMS-based motion sensors move lower in both size and price
By Margery Conner, Technical Editor -- EDN, June 9, 2009
The 16-bit, three-axis LIS302DLH digital MEMS (microelectromechanical-system) accelerometer from STMicroelectronics is 0.75 mm high and has a 3×5-mm footprint. It has a power-saving shutdown mode and wakes automatically when it detects motion. The integrated digital circuitry provides acceleration measurements to ±8g through an I2C (inter-integrated-circuit)/SPI (serial-peripheral-interface)-bus interface, allowing direct connection to the system processor with no external components required. The device sells for $1.35 (10,000).
STMicro has also introduced a family of single-axis and multiaxis MEMS gyroscopes that offer a full-scale range of 30 to 6000°/sec. The sensors simultaneously provide two separate outputs for each axis, including an unamplified output for general detection of angular motion and 4× amplification for high-resolution measurements.
The gyroscopes are stable over a wide temperature range and time, with variation typically lower than 0.05°/sec/°C for zero-rate level, eliminating the need for further temperature compensation in the application. The noise level at the output signal—0.014°/sec/
at 30°/sec full-scale—does not affect measurement precision. The devices can operate with any supply voltage of 2.7 to 3.6V and come in a 535-mm LGA package.
Two members of the new family are the LPR503AL, a two-axis pitch-and-roll gyroscope with 30 and 120°/sec full-range scales, and the LPY550AL, a two-axis pitch-and-yaw gyroscope with 500 and 2000°/sec full-range scales. The devices sell for $2.50 (10,000 or more).
