component

BMA400 — 3-axis Ultra-Low-Power Accelerometer

Unreviewed

by Kyle Bergstedt

Bosch Sensortec BMA400. 12-bit triaxial accelerometer, ±2g/±4g/±8g/±16g, <14.5µA normal mode. Step counter, activity recognition, tap detection, 1KB FIFO, SPI/I²C. LGA-12 2×2×0.95mm.

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Source: Bosch Sensortec BMA400 Data Sheet (BST-BMA400-DS000-14)
Manufacturer: Bosch Sensortec
Part Number: BMA400
Document: BST-BMA400-DS000-14 — Rev 2.3, July 2025

Description

The BMA400 is a 12-bit, digital, triaxial acceleration sensor with smart on-chip motion and position-triggered interrupt features. It is Bosch Sensortec's first ultra-low-power accelerometer, offering full programmability with an advanced set of integrated motion-detection algorithms while keeping supply current under 14.5 µA at the highest performance mode. A dedicated step counter supports extended battery life in wearables at a current consumption of only 4 µA.

The sensor targets coin-cell-powered IoT products, smartwatches, fitness trackers, and door/window alarm devices, where always-on motion detection is needed without draining the battery.

Key Specifications

Parameter Value
Resolution 12 bit
Acceleration Ranges ±2g / ±4g / ±8g / ±16g
Output Data Rate 12.5 Hz – 800 Hz
Current (normal mode) < 14.5 µA
Current (step counter only) 4 µA
Current (sleep mode) 160 nA
Current (low-power mode, 25 Hz ODR) 850 nA
Supply Voltage VDD 1.72 – 3.6 V
Supply Voltage VDDIO 1.2 – 3.6 V
Operating Temperature −40 °C to +85 °C
Package LGA-12, 2.0 × 2.0 × 0.95 mm
FIFO Depth 1024 bytes
Digital Interface I²C, SPI (4-wire and 3-wire)
Interrupt Pins 2

Features

  • Small LGA-12 package, footprint 2 mm × 2 mm, height 0.95 mm
  • Ultra-low-power operation — < 14.5 µA with highest performance
  • Programmable acceleration ranges (±2 g / ±4 g / ±8 g / ±16 g)
  • Low-pass filter bandwidth selectable at 0.48 × ODR
  • Output data rate up to 800 Hz
  • Integrated 1 KB FIFO with watermark and full interrupts
  • On-chip interrupt engine: auto-wakeup, auto-low-power, activity/in-activity
  • Step counter with 4 µA system current consumption
  • Activity recognition (walking, running, standing still)
  • Tap / double-tap detection
  • Orientation detection
  • SPI (4-wire, 3-wire), I²C, two interrupt pins
  • VDDIO range 1.2 V – 3.6 V
  • RoHS compliant, halogen-free

Pin Configuration

Pin Name Type Description
1 SDO Digital I/O Serial data output in SPI mode; I²C address-select in I²C mode
2 SDX Digital I/O SDA in I²C; SDI in 4-wire SPI; SDA in 3-wire SPI
3 VDDIO Supply Digital I/O supply voltage (1.2 – 3.6 V)
4 NC — Not connected
5 INT1 Digital I/O Interrupt output 1 (default)
6 INT2 Digital I/O Interrupt output 2 (default)
7 VDD Supply Analog and digital supply (1.62 – 3.6 V)
8 GNDIO Ground Ground for digital I/O domain
9 GND Ground Analog and digital ground
10 CSB Digital In Chip-select for SPI mode
11 NC — Not connected
12 SCX Digital In SCK in SPI mode; SCL in I²C mode

Absolute Maximum Ratings

Parameter Condition Min Max Units
Voltage at Supply Pin VDD Pin −0.3 4 V
Voltage at Supply Pin VDDIO Pin −0.3 4 V
Voltage at any Logic Pin Non-Supply Pin −0.3 VDDIO+0.3, < 4 V
Passive Storage Temp. Range ≤ 65 % rel. H. −50 +150 °C
Mechanical Shock Duration ≤ 200 µs — 10 000 g
Mechanical Shock Duration ≤ 1.0 ms — 2 000 g
Free fall onto hard surfaces — 1.8 m
ESD HBM, at any pin — 2 kV
ESD CDM — 500 V
ESD MM — 200 V

Note. Stress above these limits may cause damage to the device. Exceeding the specified electrical limits may affect reliability or cause malfunction.

Electrical Characteristics

Output Signal

Parameter Symbol Condition Min Typ Max Units
Sensitivity S2g gFS2g, TA=25 °C — 1024 — LSB/g
Sensitivity S4g gFS4g, TA=25 °C — 512 — LSB/g
Sensitivity S8g gFS8g, TA=25 °C — 256 — LSB/g
Sensitivity S16g gFS16g, TA=25 °C — 128 — LSB/g
Sensitivity Temp. Drift TCS Nominal VDD/VDDIO, gFS4g — 0.025 — %/K
Zero-g Offset Off Nominal VDD/VDDIO, gFS4g — 50 — mg
Zero-g Offset Temp. Drift TCO Nominal VDD/VDDIO, gFS4g — 1 — mg/K
Output Data Rate ODRNORM Normal mode 12.5 — 800 Hz
Output Data Rate ODRLPM Low-power mode — 25 — Hz
Bandwidth BWNORM 3 dB cutoff selectable in normal mode 0.24 × ODRNORM — 0.48 × ODRNORM Hz
Nonlinearity NL Nominal VDD/VDDIO — 0.5 — %FS
Output Noise Density nRMS Nominal VDD/VDDIO, OSR<3, X/Y-axis — 180 — µg/√Hz
Output Noise Density nRMS Nominal VDD/VDDIO, OSR<3, Z-axis — 240 — µg/√Hz

Mechanical Characteristics

Parameter Symbol Condition Typ Units
Cross-Axis Sensitivity S relative contribution between any two axes 2 %
Alignment Error EA relative to package outline 0.5 °

Current Consumption

Parameter Symbol Condition Typ Units
Supply Current — Normal mode IDD VDD=1.8 V, OSR=3 14.5 µA
Supply Current — Normal mode IDD OSR=0 3.5 µA
Supply Current — Sleep mode IDDsleep VDD=1.8 V, 25 °C 160 nA
Supply Current — Low-power mode IDDlpf VDD=1.8 V, 25 Hz ODR, OSR=0 850 nA
Wake-up Time tw_up From sleep to normal mode 2 / ODR ms
Power-Up Time ts_up From device start 1 ms

Communication Interface

Parameter Default Configurable
Primary interface I²C Yes, SPI via register
SPI modes 4-wire 4-wire / 3-wire
I²C speed Fast-mode 400 kHz Standard / Fast / Fast+
SPI clock up to 10 MHz —
Interrupt pins 2 (INT1, INT2) Mapping configurable

Applications

  • Step counting for extended-battery-life wearables
  • Always-on motion detection in IoT devices and smart watches
  • Advanced system-level power management for mobile devices
  • Fitness and activity-tracking applications
  • Tap / double-tap input detection
  • Drop detection for warranty / transport logging
  • Window/door state sensing for climate-control and alarm systems
  • Battery-powered products operating from coin cells requiring < 1 µA average and auto-wakeup functionality