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MEMS Sensors for Automotive Applications: A Glance at STMicroelectronics’ 6-Axis Inertial Module

July 18, 2018 by Robin Mitchell

While some car enthusiasts resist the integration of technology into automobiles, the industry is marching on towards more and more electronic components in cars. STMicroelectronics has announced their latest automotive-grade MEMS, the ASM330LHH, which aids in equipping cars with sensor technology.

While some car enthusiasts resist the integration of technology into automobiles, the industry is marching on towards more and more electronic components in cars. STMicroelectronics has announced their latest automotive-grade MEMS, the ASM330LHH, which aids in equipping cars with sensor technology.

Automotive vehicles have experienced some extraordinary changes over the last few decades. The first cars were mostly mechanical with basic electrical systems that provided power for spark plugs and headlights. As technology progressed, cars also found themselves being fitted with the latest gadgets and gizmos including radios, electric windows, wipers, alarms, (and even mini-fridges for champagne). GPS has made printed maps redundant and, in recent years, capacitive touch screens in infotainment centers have changed the way we interact with our cars' maintenance interfaces and comfort features.

More pressing technological advancements have also been made to vehicles for safety purposes, including better airbag deployment and even lane correction. The surge in these sensor-dependent features has challenged engineers across the industry to develop increasingly more accurate sensors with automotive applications in mind. Here's a look at a couple of MEMS sensors released specifically for automotive use.

The New Generation of Automotive Sensors

STMicroelectronics announced on July 9^th a new automotive-grade MEMS sensor, the ASM330LHH, which aims to meet the current sensor demands from modern cars. The ASM330LHH is a system-in-package which integrates a 3D digital accelerometer, gyroscope, and hardware to address automotive in non-safety applications. The sensor is AEC-Q100 qualified, has an extended temperature range from -40 to 105 degrees C, and an embedded compensator for temperature adjustments.

The sensor also integrates the following:

Accelerometer with a user-selectable full scale up to ±16g
Gyroscopic range from ±125 to ±4000 dps
SPI and I2C interface
Six-channel synchronized output (important in dead reckoning applications)
Programmable interrupts
3K FIFO

Image courtesy of STMicroelectronics.

The sensor is incredibly small measuring just 2.5mm x 3mm x 0.86mm, housed in an LGA package with 14 pins.

Typical applications for the sensor include:

Dead reckoning
Telematics and eTolling
Anti-theft systems
Impact detection
Crash reconstruction
Motion-activated related functions
Driving comfort (i.e., automatic seat adjustments)
Vibration monitoring (i.e., suspension quality)

Image courtesy of STMicroelectronics.

A Look at Other Automotive-Focused MEMS Sensors

STMicroelectronics are not the only ones involved with automotive MEMS devices; Bosch also has several devices to address this application.

The two main sensors produced by Bosch are the SMI130 and the SMI700. The SMI130 sensor is a sensor with a small footprint and low power consumption. The sensor is also AEC-Q100 qualified and is targeted at applications including navigation (for dead reckoning), vehicle dynamics logging, and car alarms.

Image courtesy of Bosch.

Its sister sensor, the SMI700, has vibration resistance and offset temperature stability. Unlike the SMI130, the SMI700 is specifically designed for use with ESP and premium vehicle dynamics control (VDC) functions such as hill-hold control, active front steering, and adaptive cruise control. The SMI700 sensor can measure data regarding rotation around the vertical axis and can deliver data about the lateral and longitudinal acceleration.

The acceleration sensor in the SMI700 uses a movable comb-like seismic mass that is suspended from silicon spring bars and fixed counter-electrodes. When external forces act on the mass (such as a sudden change in velocity), the mass deflects from its resting position which results in a change in capacitance.

Image courtesy of Bosch.

Characteristic	SMI130	SMI700
Package	LGA16	BGA34
Sensing Axes	X,Y,Z (Ω) and X, Y, Z (a)	X (Ω) and Y, Z (a)
Range	Up to ±2000 (Ω) and ±16 g (a)	Up to ±300 (Ω) and ±5 g (a)
Operating temperature	-40°C to 85°C	-40 to 125°C
Supply Voltage	3.3V	3.3V or 5V
Interface	SPI, I2C	SPI, PSI5, CAN

Table comparing the SMI130 and the SMI700. Image taken from Bosch.

As cars evolve, so must the components required to facilitate their increasingly complex functionalities. What other automotive-geared components have caught your eye?

Featured image used courtesy of STMicroelectronics.