MEMS crash sensors complete airbag kit from ST

September 23, 2015 // By Graham Prophet
STMicroelectronics has introduced two central airbag crash sensors alongside its peripheral crash sensors, airbag system ICs, and safety microcontrollers, creating a complete airbag-electronics kit that supports stringent automotive-application and functional-safety requirements.

The AIS1120SX and AIS2120SX single- and dual-axis 120g in-plane MEMS accelerometers are designed to be mounted in the vehicle’s Airbag Control Unit (ACU) responsible for evaluating the sensor data and triggering the appropriate restraint system.

Each sensor includes two independent sensing channels for redundancy and incorporates both slow and fast offset cancellation as well as precise temperature compensation for optimum stability. Built-in power-on self-test ensures reliability and run-time diagnostics help developers achieve the required level of functional safety. Both sensors have standard 400 Hz signal bandwidth, which the engineer can extend to 1600 Hz.

ST has used its MEMS technology to integrate the precision mechanical sensing element in the same package with a 3.3V-compatible interface IC featuring a 14-bit digital SPI output.

The AIS1120SX and AIS2120SX sensors are specified over the extended temperature range from -40°C to +105°C. They will enter full production in Q1 2016 in a plastic fully-moulded SOIC8 package.

ST offers the devices as a package that includes a safety microcontroller, which coordinates airbag activation. Three airbag system ICs, the L9678, L9679, and L9680 meet the demands of applications ranging from entry or mid-level to high-end vehicles with multiple airbag firing loops. These devices, which integrate system power management, sensor interfaces, switch interfaces, and arming safety logic, are responsible for decoding the sensor data and forwarding results to the microcontroller. Based on the 32-bit Power Architecture, ST’s SPC5 automotive microcontroller family includes Safety Line devices that offer a choice of single- or dual-core configurations with up to 1 Mbyte of Flash. Multiple DSPI (Deserial Serial Peripheral Interface) channels optimise system and diagnostic control. A Fault Collection and Control Unit (FCCU) and built-in self-tests provide safety coverage for ASIL (Automotive Safety Integrity Level) development.