SMA560 MEMS acceleration sensor for airbag control units Bosch acceleration sensors – more functions in even less space More than 40 percent space saving

21st February 2011
ES Admin
The dual-axis SMA560 model for airbag control units marks Bosch’s entry into the fifth generation of micro-mechanical acceleration sensors. As opposed to sensors of the previous generation, this new model, in its SOIC8 housing, combines space savings of more than 40 percent with an unprecedented variety of functions. This means that circuit designers can assign one of four measuring ranges to each sensing axis independently. Via the serial peripheral interface, the sensor outputs the measuring values in either Bosch-SPI or Open-SPI format. The SMA560 can currently be ordered as a sample. The SMA550 sensor is available with the same parameters but with only one sensing axis – both are RoHs-compliant.
Flexible application
With two sensing axes, the SMA560 is ideal as a central sensor for the detection of frontal and side impacts. To record the different deceleration forces with even greater accuracy, application engineers can set the sensor’s measuring ranges for the two axes as required – to ±35 g, ±48 g, ±70 g, or ±96 g. The sensor can be operated with an operating voltage of 3.3 or 5 volts and consumes significantly less power than its predecessor. The wide operating temperature range of –40 °C to +105 °C and a self-test integrated into the sensor’s electronics ensure that the high standards of operating reliability required for airbag components are met. The bi-directional 16-bit SPI interface provides the measuring signal in 10-bit resolution.

In the fifth generation as well, Bosch’s sensor developers have elected to keep the tried and tested dual-chip solution within the sensor. Micro-machined microscopic springs and weights form the capacitive readings recorder; just one millimeter from this, an ASIC integrated into the sensor housing takes care of the signal conditioning and other electronic functions. Depending on the measurement values of the acceleration sensor, a control unit decides whether to activate the restraint systems, such as airbags and seat belt tensioners.

Expertise of the leading MEMS sensor manufacturer
From the very beginning, Bosch has played a key role in the development of MEMS technology (Micro-Electro-Mechanical Systems). The company has produced well over one billion MEMS sensors since production began in 1995. Some 220 million sensors left its Reutlingen plant in 2009, making Bosch the leading provider in the global MEMS sensor market. The company’s product portfolio includes pressure, acceleration, and yaw-rate sensors for numerous applications in the automotive industry and consumer electronics. The first MEMS acceleration sensors for airbag systems were launched in 1996, at that stage still in the PLCC28 package. The package size has been reduced step by step as a result of continuous further development. The SOIC16 package premiered in 2002; the SOIC14 package followed in 2006, and now gives way to the even smaller SOIC8 variant. For more information on Bosch’s sensor program, go to

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