Issue: May 2010


Freescale Introduces Automotive Airbag System Products for PSI5 Standard



Advanced Integrated Satellite Sensor Family, Airbag System Basis Chip and ECU Inertial Sensors Enable Complete PSI5 Airbag Solution

by Lenny Case

At the PSI5 Forum in Nuremberg, Germany, Freescale Semiconductor introduced two advanced airbag system solutions for the emerging Peripheral Sensor Interface 5 (PSI5) protocol, including an inertial satellite sensor family and a mixed signal analog IC. The company 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.

“PSI5 is designed to be a flexible communication protocol that meets requirements for automotive sensors, such as those found in airbag systems.”
.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 in the forefront.

“Freescale’s solution enables a reduction in complexity and development time of airbag systems while improving reliability through its automotive sensor and analog solutions,” said Tom Deitrich, senior vice president and general manager of Freescale’s RF, Analog 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.”

Adding to an extensive product portfolio for next-generation airbag applications, including components for the Distributed Systems Interface (DSI), Freescale’s PSI5 airbag system solutions leverage the company’s SMARTMOS technology for a high level of system integration available worldwide. 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 overdamped 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.

MMA5xxxW Product Features

•±60 g to ±480 g full-scale range
•Selectable 400 Hz, 3 pole or 4 pole low-pass filter
•16-Pin 6 x 6 mm QFN package with solder visibility for inspection after mounting
•PSI5 version 1.3 compatible
•Two-wire programming mode 

Freescale’s MC33789 SBC is a mixed signal analog IC for airbag safety applications. The MC33789 SBC 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.

MC33789 Product Features

•Four satellite sensor master interfaces compatible with PSI5 V1.3
•Nine configurable switch input monitors with diagnosis capability
•Multiple voltage output supplies including energy reserve control
•Safing state machine with programmable sensing thresholds
•16-bit SPI up to 8 MHz and LIN 2.1 physical layer interface 

The MMA68xxQ digital inertial sensor family is designed as a main crash sensor or a safing sensor in airbag applications. The overdamped 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.

MMA68xxQ Product Features

•±20g to ±120 g full-scale range, independently specified for each axis
•3.3 V or 5 V single supply operation
•SPI-compatible serial interface
•10-bit digital signed or unsigned SPI data output
•Independent programmable arming functions for each axis that simplifies design
Pricing and availability

The MMA52xxW X-Axis satellite inertial sensor family is available now for a suggested resale starting price of $2.99 (USD) in 10,000-piece quantities. The MMA51xxW Z-Axis satellite inertial sensor family is available now, with production quantities planned for third quarter 2010.

The MC33789 airbag system basis chip is available now for a suggested resale price of $4.38 (USD) in 10,000-piece quantities.

The MMA68xxQ XY-Axis airbag inertial sensor family is available now for a suggested resale starting price of $2.80 (USD) in 10,000-piece quantities.

For more information about Freescale’s automotive portfolio, visit www.freescale.com/automotive.

About PSI5 & PSI5 V.1.3

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.

To learn more about the PSI5 standard, membership requirements and to gain access to the latest specifications, product links, application notes and contacts, visit www.psi5.org  

About the Freescale Technology Forum

Created to drive innovation and collaboration, the Freescale Technology Forum (FTF) has become the developer event of the year for the embedded semiconductor industry. The Forum has drawn more than 35,000 attendees at FTF events worldwide since its inception in 2005. For more information about FTF, go to: www.freescale.com/ftf 

About Freescale Semiconductor

Freescale Semiconductor is a global leader in the design and manufacture of embedded semiconductors for the automotive, consumer, industrial and networking markets. The privately held company is based in Austin, Texas, and has design, research and development, manufacturing or sales operations around the world. www.freescale.com

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