SCIENCE

The development of safer vehicles is a key technology driver for the automotive industry, with airbag safety systems leading the charge. The U.S. National Highway Traffic Safety Administration (NHTSA) estimates that frontal air bags alone saved more than 25,780 lives between 1987 and 2008. As automotive suppliers continue to incorporate critical safety features in their designs, they must continue improving performance, while at the same time reducing cost to gain a competitive edge.

To address these demands, Freescale Semiconductor today unveiled two additions to its Xtrinsic line of intelligent sensing solutions specifically designed for enhanced automotive passenger safety. Freescale developed the MMA16xxW and MMA26xxW for airbag safety systems that use the widely adopted Distributed Systems Interface (DSI) 2.5 standard to connect remotely placed pressure, acceleration, occupant and buckle sensors to the main airbag electronic control unit (ECU). The DSI protocol supports point-to-point, parallel and daisy-chain networks. Pioneered by Freescale, Denso and TRW, the DSI protocol has been adopted by the world's leading manufacturers of supplemental restraint system (SRS) airbags.
 
“As advancements are made in vehicle safety design, the importance of sensors in the vehicle is growing,” said Demetre Kondylis, vice president and general manager of Freescale’s Sensor & Actuator Solutions Division. “By incorporating sensors into their designs, our automotive customers continue to bring to market vehicles with leading-edge safety features. Adding support for the DSI 2.5 protocol to our Xtrinsic line of sensors is one more way we’re providing the automotive solutions our customers need.”

The Xtrinsic MMA16xxW and MMA26xxW products are prominent additions to Freescale’s portfolio of next-generation airbag solutions, which includes products that support the Peripheral Sensor Interface 5 (PSI5) protocol. The Xtrinsic MMA16xxW and MMA26xxW accelerometers have integrated features that enable higher levels of system integration and intelligence to provide a more instant and intuitive crash response. The inertial satellite sensors are positioned around the car to collect sensing inputs and integrate signals for optimal front and side crash detection.

Freescale is one of the only suppliers with both X- and Z-axis over-damped inertial satellite sensors housed in a quad flat no-lead (QFN) package, which provide a smaller footprint and more flexibility for module orientation in vehicles. The over-damped response of the inertial sensor minimizes signal distortion when subjected to high magnitude and high-frequency shocks that are present during vehicle crashes. An accurate signal allows the system to properly calculate the need for airbag deployment during a crash.

The Xtrinsic MMA16xxW and MMA26xxW sensors enable a 2 kHz or higher output data rate and up to four sensors on the same bus. These features allow designers to incorporate more functionality while decreasing the bill of materials. The MMA26xxW also supports a bus switch, which enables the airbag system to reconfigure in case of satellite module failure to help ensure an always-connected safety environment.

Feature Summary:

• ±50 g to ±312.5 g, nominal full-scale range, X-axis, or Z-axis
• Selectable 180 Hz, two pole, 400 Hz, four pole, or 800 Hz, four pole low-pass filter
• DSI 2.5 compliant, with full support of mandatory commands
• 16 us internal sample rate, with interpolation to 1 us
• -40 degrees C to +125 degrees C operating temperature range
• QFN 6x6 mm 16-pin package
• Qualified AEC-Q100, Revision G, Grade 1 (-40 degrees C to +125 degrees C)

 
Development support, price and availability
The Xtrinsic MMA16xxW and MMA26xxW accelerometers are available now for a suggested resale price (USD) starting at $2.99 in 10,000-piece quantities.

Freescale’s Tower Sensor Development Tool offers a modular, reconfigurable demonstration and development platform to provide an easier development cycle. It provides expansion cards plugged into backplane boards called the elevator and hosts a single MCU/MPU story as the main control board. The swappable plug-ins allows designers to rapidly evaluate and compare the Xtrinsic MMA16xxW and MMA26xxW inertial satellite accelerometers. The TWRPI-DSI2.5 plug-in accelerometer boards are available for a suggested resale price of $15.00 (USD).

The Xtrinsic MMA16xxW and MMA26xxW accelerometers are included in Freescale’s product longevity program, with assured supply for a minimum of 15 years.