Freescale Introduces Automotive Airbag System Products for PSI5 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 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 MMA68xxQ 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