May 24, 2012 — Bosch Sensortec, the consumer electronics sensor arm of Bosch, has integrated two triaxial micro electro mechanical systems (MEMS) sensors in 1 package, claiming the smallest inertial measurement unit (IMU) to date. An optional geomagnetic sensor creates a 3DoF module. Solid State Technology spoke with Leopold Beer, director of global marketing at Bosch Sensortec, about MEMS integration and the sensor fusion software element of sensing.
The BMI055 combines an acceleration sensor and a gyroscope for advanced consumer electronics applications with six degrees of freedom (6DoF), such as gaming applications in smartphones, tablets, consoles, etc. It is packaged in a 3.0 x 4.5 x 0.95mm LGA.
The BMI055 is enabled by continuing miniaturization of MEMS, Beer noted, adding that Bosch fabs all of its MEMS chips in house with high-volume and high-reliability production.
Power is also important for the 2 MEMS package. The accelerometer and higher-power-consuming gyroscope can operate independently, when sensor fusion is not required.
“The MEMS are full-performance sensors in their own right, because customers are used to a certain set of functionality from accelerometers and gyroscopes,” Beer said, “that cannot be compromised for small form factor.”
The accelerometer features flexible interrupt functionality and integrated FIFO buffer. The gyroscope features an integrated interrupt engine, integrated FIFO buffer, and 4 offset compensation modes. For greater design flexibility, the measurement range of the sensors is programmable: ±125°/s to ±2000°/s for the gyroscope, and ±2g to ±16g for the accelerometer. The latter also shows a low zero-g offset of typically 70 milli-g. The gyroscope has a 16 bit resolution; the accelerometer’s is 12 bit. The gyroscope boasts stable operation with good TCO and offset compensation. The package offers good signal to noise ratio. I2C and SPI digital interfaces offer versatile communication options.
The BMI055 IMU is released concurrently with Bosch’s custom sensor fusion software BSX2.0 FusionLib that optimizes sensing by combining input from the gyroscope and accelerometer. MEMS manufacturers know the functionality and performance of each type of MEMS sensor best, Beer said. Therefore, MEMS makers are the ideal designers of MEMS sensor fusion software. “The algorithms in MEMS software do more than just drive the chip, they integrate abilities from each MEMS to improve calibration, interference filtering, and more.” Sensor fusion, for example, combines the good angular resolution but high drift of gyroscope MEMS with the slower eCompass, improving accuracy. BSX2.0 FusionLib works with all stand-alone or integrated Bosch Sensortec MEMS devices.
Bosch Sensortec makes MEMS devices for consumer applications, as a division of Bosch. Learn more at www.bosch-sensortec.com.