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Freescale sensors put the brakes on vehicle instability


Intelligent sensors help car makers meet U.S. and global automotive safety requirements

MA670xEG Accelerometers for Electronic Stability Control

TOKYO (Freescale Technology Forum Japan). – Automotive safety systems are becoming more intelligent with Freescale Semiconductor’s advanced low acceleration level (low-g) inertial sensors for electronic stability control (ESC) systems. ESC helps drivers maintain control of their vehicles by using high-performance, low-g 2-axis sensors to measure the lateral and longitudinal acceleration of the vehicle. When sensors register potentially unstable driving conditions, the system sends data to the car’s engine and braking system to automatically assist the driver in maintaining vehicle control.

Freescale’s MMA6700/1EG accelerometers offer a wide dynamic range with exceptionally high resolution. This increased dynamic range enables ESC designers to filter out extraneous signals, such as parasitic vibrations, that could potentially interfere with the vehicle’s lateral acceleration measurement. In addition, the accelerometers’ integrated digital signal processor (DSP) provides higher accuracy and improves signal integrity for ESC applications.

“Boosted by government-mandated changes affecting the safety of new vehicles in key North American and European automotive markets, the demand for low-g sensors required in electronic stability control systems will grow at double digit rates over the next five years,” said Richard Dixon, a senior analyst for MEMS at iSuppli Corp. “Companies attracted to this space first need the developmental muscle to develop MEMS accelerometers to the requisite stringent levels of precision and reliability, and second, to overcome an entrenched supply chain. Freescale is in a strong position to excel in the automotive sensor market.”

According to iSuppli, ESC systems in automobiles will rise to nearly 48 million units in 2012, up from just 23.1 million in 2007. Because these ESC systems incorporate MEMS sensors to detect instability and potential rollover conditions in vehicles, iSuppli believes the MEMS sensor market will see a similar jump, reaching sales of $715 million by 2012, up from $378 million in 2006.

What’s driving the projected MEMS market growth is a mandate from the National Highway Traffic Safety Administration (NHTSA) that will require ESC systems on 100 percent of passenger cars, multipurpose vehicles, trucks and buses sold in the United States by model year 2012. NHTSA estimates that 5,300 to 9,600 lives will be saved and up to 238,000 injuries will be prevented annually once all light vehicles (vehicles weighing 10,000 pounds or less) are equipped with ESC systems. ESC has been a standard feature on high-end vehicles for several years and now is appearing in entry-level and mid-range vehicles. Sport utility vehicles (SUVs) especially benefit from ESC due to higher rollover rates.

“Automotive OEMs are looking for a cost-effective, high-performance solution as ESC safety mandates are expanding throughout North America, China, India and other parts of the world,” said Demetre Kondylis, vice president and general manager of Freescale’s Sensor & Actuator Solutions Division. ”Freescale’s low-g accelerometer offers developers higher levels of accuracy and greater flexibility in a single device, which helps save system cost and valuable board space.”

In addition to providing an optimal motion-sensing solution for ESC applications, Freescale’s low-g accelerometers are designed for myriad embedded applications that require measurement of small forces such as those resulting from shock, vibration, tilt, movement or acceleration. From washing machines, sports medicine equipment and video game pads to seismic detectors and security systems, consumer and industrial manufacturers are using low-g accelerometers to differentiate their products with safety, security and convenience features.

About HARMEMS technology
MMA6700/1EG accelerometers are based on Freescale’s next-generation high aspect ratio micro-electromechanical systems (HARMEMS) technology, a proven technology for airbag sensing applications. The accelerometers have an advanced transducer design that enhances sensor offset performance. HARMEMS technology provides over-damped mechanical response and exceptional signal-to-noise ratio to address customer requirements. Since the ESC system is installed either in the vehicle cabin or under the hood, over-damped HARMEMS technology enables a high degree of immunity to high-frequency, high-amplitude parasitic vibrations. For ESC applications, the higher signal-to-noise ratio combined with Freescale’s DSP-based signal chain is designed to provide both a wide range and high sensitivity with less than one least significant bit (LSB) noise.

MMA6700/1EG product features

* XY-axis of sensitivity in one device
* 10- or 11-bit digital data output
* +/- 3.5 or +/- 5 g full-scale range per axis
o MMA6700EG: ±3.5 g (11-bit data sensitivity = 3.43 mg/digit typical at 25 degrees C)
o MMA6701EG: ±5 g (11-bit data sensitivity = 4.91 mg/digit typical at 25 degrees C)
* Selection of integrated signal conditioning low-pass filters
* SPI-compatible serial interface
* Bidirectional internal self-test
* On-chip temperature sensor and voltage regulator
* Support for signed or unsigned output data
* Capture/hold input for system-wide synchronization support
* 3.3 V or 5 V single supply operation
* Ratiometric analog voltage output
* Five customer-assigned, one-time-programmable (OTP) bytes
* Minimal external component requirements
* Wide operating temperature range from -40 degrees C to +125 degrees C
* Robust 20-pin SOIC wide-body RoHS-compliant package

Pricing and availability
Samples of the MMA6700/1EG devices are available now to automotive customers. The suggested resale price in 10,000-piece quantities starts at $7.67 (USD) for the MMA6700EG and the MMA6701EG.


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