SMI230 — 6DoF Inertial Sensor for Automotive Applications

Source: Bosch Technical Product Description (V2.1, Feb 2022)
Manufacturer: Robert Bosch GmbH
Part Number: SMI230 (0273 142 144)
Document: Technical Product Description V2.1 — Feb 2022

Description

The SMI230 is a combined triaxial accelerometer and triaxial gyroscope (6 degrees of freedom) for non-safety automotive applications such as in-dash navigation. It is based on a two-chip stacked concept: the accelerometer and gyroscope sensing elements (MEMS) are mounted side-by-side, with read-out ASICs stacked on top of each respective sensing element, all within a single LGA-16 package.

The accelerometer detects differential capacitance changes from comb-like seismic masses suspended on silicon spring bars. The gyroscope uses the Coriolis vibratory principle with two seismic masses oscillating at ~25 kHz via electrostatic drive forces. Both sensors feed through hybrid analog-digital converters (ADCs) at 400 kHz sampling rate into digital signal processors (DSPs) with configurable low-pass filtering, gain, and offset correction.

The gyroscope and accelerometer can be operated individually or tied together for data synchronization. The device supports SPI (up to 10 MHz) and TWI/I2C (up to 400 kHz) interfaces with separate chip selects for each sensor.

Key Specifications

Features

• Combined 16-bit triaxial accelerometer and 16-bit triaxial gyroscope in a single package
• Accelerometer and gyroscope operable individually or synchronized via data synchronization feature
• Selectable measurement ranges: +/-2/4/8/16 g (accel), +/-125/250/500/1000/2000 deg/s (gyro)
• Configurable low-pass filter bandwidth with bypass option
• On-chip FIFO buffers for both accelerometer and gyroscope
• Configurable interrupt engine: any-motion, no-motion, high-g, low-g, orientation detection
• On-chip temperature sensor (-104 to +150 degC, 11-bit, 0.125 K/LSB)
• SPI and TWI/I2C digital interfaces with separate chip selects
• Power-on reset (POR) generator
• 5 power modes per sensor (normal, suspend, deep suspend for gyro)
• Self-test capability for both sensors
• AEC-Q100 Grade 2 qualified, MSL1, RoHS compliant, halogen-free
• Mechanical shock tolerance up to 10,000 g (duration <=200 us)
• Application support software and config file upload capability

Pin Configuration

TWI/I2C Addresses:

Absolute Maximum Ratings

Recommended Operating Conditions

Lifetime conditions are per AEC-Q100 Grade 2 requirements.

Electrical Characteristics

Power Supply

No limitations on VDD/VDDIO relative voltage levels as long as each is within operating range. Device can be switched off (VDD=0V) while keeping VDDIO on, or vice versa.

Accelerometer

Default config: +/-2 g range, 47 Hz bandwidth (100 Hz ODR).

Gyroscope

Default config: +/-2000 deg/s range, 47 Hz bandwidth.

Temperature Sensor

Power Consumption

Power Modes — Accelerometer

Power Modes — Gyroscope

Communication Interface

SPI Interface

4-wire SPI with separate chip selects for accelerometer (CSB1, pin 14) and gyroscope (CSB2, pin 5). Compatible with SPI modes 00 and 11 (auto-selected based on SCK state at CSB falling edge).

Important: When reading the accelerometer via SPI, a dummy byte is sent first. A single byte read requires reading 2 bytes in burst mode (discard the first byte). For burst reads (e.g., 6 bytes of accel data from 0x12), read 7 bytes and discard the first.

TWI/I2C Interface

Compatible with I2C standard and fast mode (7-bit address only). Supports burst read with auto-incrementing address. Internal watchdog timer prevents bus lockup.

Limitations: Only single byte write supported. No clock stretching. Minimum data hold time of 120 ns (spec is 300 ns). Only 7-bit address mode.

Software API

Device Initialization

After power-on, the device performs a power-on reset (POR) which resets all registers to defaults. Application-specific settings must be reconfigured after POR. The accelerometer interface type (SPI/TWI) is determined by the CSB1 pin state during POR. The gyroscope interface type is determined by the PS pin.

Accelerometer Register Map (Key Registers)

Gyroscope Register Map (Key Registers)

Data Synchronization

The accelerometer and gyroscope can be synchronized so that acceleration and angular rate data correspond to the same timestamp. This requires uploading a configuration file to the accelerometer's feature engine. When enabled, synchronized data is available through dedicated registers (INT_SYNC_X/Y/Z at 0x1E-0x28).

Interrupt Features

Configurable via config file upload to the accelerometer feature engine:

• Any-motion / Slope detection — detects sudden acceleration changes
• High-g detection — detects acceleration exceeding a programmable threshold
• Low-g detection — detects free-fall or low-gravity conditions
• Orientation detection — detects device orientation relative to gravity (portrait/landscape, face-up/face-down)
• No-motion detection — detects when device is stationary

FIFO Operation

Both accelerometer and gyroscope have independent on-chip FIFO buffers:

• Accelerometer FIFO: up to 1024 bytes, supports FIFO, stream, and stream-to-FIFO modes
• Gyroscope FIFO: up to 100 frames, supports FIFO and stream modes
• Configurable watermark interrupts and overrun detection

Self-Test

• Accelerometer: Apply electrostatic self-test force, verify output difference is within specified range
• Gyroscope: Triggered by writing to GYRO_SELF_TEST register, bit 0 of result indicates pass/fail

Thermal Information

Reflow Soldering Profile (Pb-Free)

MSL rating: JEDEC Level 1

Packages

Tolerances: +/-0.05 mm unless otherwise specified. Compliant with RoHS (2002/95/EC), WEEE (2012/19/EU), and halogen-free.

Applications

• High-end dead reckoning navigation
• eCall systems
• Telematics and electronic tolling
• Vehicle dynamics data logging
• Car alarm / anti-theft
• ADAS sensor fusion