Freescale Xtrinsic intelligent sensors help keep drivers safe

Automobiles have included passive safety systems, such as airbags and seatbelts, for years to minimize injuries from crashes. Recently, the industry began incorporating sophisticated, intelligent active safety systems to help prevent accidents from occurring. Electronic stability control (ESC) is an example of an active safety system that proactively helps safeguard passengers through the use of multiple smart sensors that monitor the driving environment.

According to the U.S. National Highway Traffic Safety Administration (NHTSA), ESC could have prevented nearly one-third of all fatal car accidents. Therefore, NHTSA is mandating that most 2012 model year vehicles include this technology. ESC helps drivers maintain control of their vehicles by using high-performance, low-g two-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 is a leader in providing sensor technology that supports automotive manufacturers as more intelligence and connectivity are incorporated into their vehicle designs,” said Demetre Kondylis, vice president and general manager of Freescale’s Sensor & Actuator Solutions Division. “With the new Xtrinsic intelligent accelerometers for advanced safety, Freescale allows designers to reduce space and cost in order in advance of critical safety standards.”

The Xtrinsic MMA6900Q and MMA6901Q accelerometers offer a wide dynamic range of sensing, with exceptionally high resolution. Designers of advanced automotive safety systems are able to filter out extraneous signals, such as parasitic vibrations, that could potentially interfere with the vehicle’s lateral acceleration measurement.

The Xtrinsic MMA6900Q and MMA6901Q accelerometers are based on Freescale’s next-generation, high-aspect-ratio microelectromechanical systems (HARMEMS) technology, a proven technology for airbag sensing applications. Not only will this technology improve the robustness of the sensor, but HARMEMS technology provides over-damped mechanical response and exceptional signal-to-noise ratio to address customer requirements. Over-damped HARMEMS technology enables a high degree of immunity to high-frequency, high-amplitude parasitic vibrations ­– a key feature since active safety applications, like ESC, are typically installed in the vehicle cabin or under the hood.

For ESC applications, the higher signal-to-noise ratio combined with Freescale’s DSP-based signal chain is designed to provide a wide range and high sensitivity with less than one least significant bit (LSB) noise. For MMA6900Q and MMA6901Q technical specifications, visit www.freescale.com/sensors.

In addition to providing an optimal solution for active safety applications, Freescale’s low-g accelerometers are applicable for myriad embedded applications that require measurement of small forces, like those resulting from shock, vibration, tilt, movement or acceleration. From industrial machines to robots and heavy-duty agricultural equipment, industrial manufacturers are using low-g accelerometers to differentiate their products with safety, security and convenience features.

Feature Summary:

* ±3.5 g or ±5 g full-scale range per axis
o MMA6900Q: ±3.5 g (11-bit data sensitivity = 3.43 mg/digit typical at 25 degrees C)
o MMA6901Q: ±5 g (11-bit data sensitivity = 4.91 mg/digit typical at 25 degrees C)
* MMA6900Q key performance:
o Low detection threshold of 8.6 mg (acceleration) or >= 0.5 degrees (angle)
o Offset tolerance value at 25 degrees C (+/- 30 mg) and over temperature (+/-50 mg)
* MMA690xQ:
o Embedded signal processing including fault and overload diagnostic flagging
o 11-bit SPI-compatible digital data
o Bidirectional internal self-test
o Qualified AEC-Q100
o Wide operating temperature range from -40 degrees C to +105 degrees C
o Over-damped transducer
o Robust 6 x 6 mm QFN package with greater than 100 kHz package resonance frequency
o 3.3 V or 5 V single supply operation