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The new triaxial acceleration sensors BMA280 and BMA255 from Bosch Sensortec feature 14 bit and 12 bit resolutions respectively – the norm up to now has been 10 bit. With this product extension Bosch Sensortec is the only manufacturer in the world to offer a complete acceleration sensor product portfolio in 2 x 2 mm package size. The new sensors even measure very small changes in acceleration of as low as 0.25 milli-g. Currently no other 2 x 2 mm acceleration sensor features such high sensitivity while maintaining an exceptionally low noise level of only 120 micro-g/vHz and 150 micro-g/vHz respectively. The 14 bit and 12 bit resolutions place great demands on the integrated electronics, yet the sensors require only 130 micro amps even at maximum data rate. In power-saving mode, at reduced data rate, the power consumption even drops to below 10 micro amps.

Dr. Frank Melzer, CEO of Bosch Sensortec, states that this latest product innovation proves again that Bosch is the world’s leading MEMS sensor manufacturer: “The fact that these sensors are the smallest size available on the market, have the lowest power consumption and low noise levels, demonstrates Bosch’s undisputed leadership in terms of MEMS technology.”

Advanced interrupt engine
Compared with existing acceleration sensors in the 2 x 2 mm series, the BMA280 and the BMA255 have an enhanced interrupt engine. The integrated interrupt engine enables them to automatically identify specific motion patterns. Previously the interrupt engine was able to recognize tapping on the housing of a mobile device, detect falling of a device or the lifting of a cell phone from a desk. Now, both types of sensors feature the additional pattern “no motion”: this means they can detect whether the device has stopped moving for a definable period of time. The energy management system of a mobile device can use this information to switch off high-performance functions until the acceleration sensor signals a new motion.

Another new feature is a FIFO buffer. It enables the sensor to buffer measurement data independently until it is required by the system. This reduces the application processors data polling frequency and hence reduces the system’s power consumption.

Manufactured on 200 mm wafers
The new sensors, already in series production, are manufactured in Bosch’s 200 mm wafer fab in Reutlingen. This new wafer fab was set up at an investment of more than 600 million euros and complements Bosch’s existing 150 mm wafer fab. Both fabs are used in the manufacture of integrated circuits (IC) and micromechanical devices (MEMS) for use in automobile technology and in consumer electronics.

Acceleration sensors in the 2 x 2 mm series from Bosch Sensortec
	BMA280	BMA255	BMA250	BMA222	BMA220
Measuring ranges  (programmable)	±2 g, ±4 g, ±8 g, ±16 g
Digital resolution	14 Bit	12 Bit	10 Bit	8 Bit	6 Bit
maximum resolution  (in the measuring range ±2 g)	0.244 Milli-g	0.98 Milli-g	3.91 Milli-g	15.63 Milli-g	62.5 Milli-g
Interfaces	SPI (3- or 4-wire) and I2C
Number of interrupt pins	2				1
Permissible operating temperature	-40 °C ... +85 °C