Inflating to a standard

01 June 2010

Freescale has introduced two airbag system solutions for the PSI5 protocol
Freescale has introduced two airbag system solutions for the PSI5 protocol

Freescale has introduced two airbag system solutions for the PSI5 protocol.

At the recent PSI5 Forum in Nuremberg, Germany, the company launched the solutions for the emerging Peripheral Sensor Interface 5 (PSI5) protocol, including an inertial satellite sensor family and a mixed signal analogue IC. It is also complementing these products with the addition of an electronic control unit (ECU) inertial sensor family. Freescale’s airbag safety products are targeted at airbag systems that are based on the PSI5 open standard.

As automotive airbag systems continue to enhance passenger safety through the incorporation of more airbags and increasingly sophisticated crash detection capabilities, automotive suppliers face continuing pressure from the market to improve performance while reducing overhead costs. Freescale’s PSI5-based solutions are developed with this in mind as both of these trends are expected to intensify as the focus on safety remains at the forefront.

“Freescale’s solution enables a reduction in complexity and development time of airbag systems while improving reliability through its automotive sensor and analogue solutions,” said Tom Deitrich, Senior Vice President and General Manager of Freescale’s RF, Analogue and Sensors Group. “PSI5 is designed to be a flexible communication protocol that meets requirements for automotive sensors, such as those found in airbag systems.”

The system uses the company’s SMARTMOS technology for a high level of system integration. Freescale’s PSI5 solutions include the micro-electromechanical (MEMS)-based MMA5xxxW satellite accelerometer portfolio and the MC33789 Airbag System Basis Chip (SBC). The MEMS-based MMA68xxW dual-axis SPI inertial sensor for the main ECU facilitates a complete airbag system solution.

Freescale’s MMA5xxxW is the industry’s first PSI5 X- or Z-axis satellite inertial sensor in a Quad Flat No-Lead (QFN) package designed for a smaller footprint compared to other SOIC-based solutions currently available. The MMA5xxxW inertial sensor family enables smaller and more robust front and side airbag satellite solutions, and improved system reliability against parasitic vibrations due to Freescale’s advanced over-damped transducer. Compatible with the PSI5 rev 1.3 standard protocol, these inertial sensors can be easily integrated as part of an overall PSI5 airbag system, and also include a bus-switch drive enabling very cost effective daisy chain configurations.

MC33789 SBC is a mixed signal analogue IC for airbag safety applications. It provides a cost effective and flexible system IC solution partitioning across the range of airbag partitions used in cars and trucks. The MC33789 SBC can be used to detect seat belt switch input states and communicate with remote crash sensors via new PSI5 master interfaces to meet industry standards. The MC33789 SBC is well suited for low to high-end airbag safety systems by allowing the designer to scale a design across a wide range of firing loops while providing enhanced safety and system reliability.

The MMA68xxQ digital inertial sensor family is designed as a main crash sensor or a safety sensor in airbag applications. The over-damped transducer coupled with a high resonant frequency package provide increased immunity to overload conditions induced by high magnitude and high frequency shocks encountered in crash detection applications. These features help to enable more robust airbag designs, while the QFN 6x6 also enables a smaller footprint compared to other SOIC based solutions currently.

The PSI5 technical specification version 1.3 is a joint development between Autoliv, Bosch, and Continental, with Freescale and TRW serving as two of the associate members. PSI5 is an open standard based on existing sensor interfaces for peripheral airbag sensors, already proven in millions of airbag systems. The sensor data can be transmitted both synchronously and asynchronously via a dual-wire interface. The technical characteristics and the low implementation overhead make the PSI5 communication protocol also suitable for many other automotive sensor applications.


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