GENERAL DESCRIPTION
The BMA400 is the first real ultra-low power acceleration sensor
without compromising on performance. Featuring 12-bit digital
resolution, continuous measurement and a defined selectable
bandwidth combined with ultra-low power the BMA400 allows
low-noise measurement of accelerations in three perpendicular
axes. The BMA400 thus senses tilt, orientation, tab/double tab,
and enables plug ’n’ play step counting with activity recognition
especially suited for wearable devices, which need a long-lasting
battery lifetime. Thanks to the continuous measurement principle
and always-defined bandwidth, the BMA400 is the ideal solution
for smart home applications such as smart indoor climate
systems and smart home security systems. In the latter, the
BMA400 can distinguish between real alarm situations like
broken glass and false signals coming from random vibrations.
Thereby, the new acceleration sensor avoids false alarms.
SENSOR FEATURES
With its embedded features the BMA400 is unique in the class of
ultra-low current accelerometers for wearable devices, smart
home- and Internet of Things applications. The embedded step
counter and activity recognition enables low current step-
counting and activity tracking at only 4 µA overall current
consumption. The plug’n’ play step counter is optimized for wrist
band usage and can also be used in other wearable devices.
On top, the BMA400 integrates a multitude of other features
(e.g. activity change, orientation, tab/double tab etc.) that
facilitate its use especially in wearable devices and increase
battery life significantly. Featuring continuous measurement and
low pass filters in all power/noise configurations down to 3.2 µA,
the BMA400 is robust to vibrations and aliasing. In an additional
ultra-low power mode the current consumption can be reduced
even further, down to 800 nA. This mode offers an auto wake-up
function to switch the sensor into any normal mode configuration
when precise measurement is required. In addition, an auto
ultra-low power feature is available to switch the sensor into its
lowest current consumption configuration, when simple motion
monitoring is needed. The BMA400 is highly configurable in
terms of current consumption and noise performance in order to
give the designer full flexibility when integrating the sensor into
an always-on low power system. The integrated features enable
the sensor to be used as main part of a power management unit.
BMA400 Technical data
Measurement range
±2 g, ±4 g, ±8 g, ±16 g
Digital resolution
12 bit
Output Data Rate (ODR)
12.5 Hz to 800 Hz
Low path filter
bandwidth
Selectable 0.48xODR or
0.24xODR
Current consumption
(independent from ODR
due to continuous
measurement)
Max. performance: 14 µA
Typical use case: < 8 µA
Low power use case: < 4 µA
Noise density
Max. performance: < 220 µg/√Hz
Typical use case: < 320 µg/√Hz
Low power: < 600 µg/√Hz
Ultra low power /
Auto-wake-up mode
800 nA @ 25 Hz ODR
Embedded features
- Step counter (< 4 µA overall)
- Activity recognition (walking,
running, standing still)
- Activity change
- Orientation
- Tab/Double tab (< 8 µA overall)
- General interrupt 1 and 2
(programmable via thresholds,
timer, logical AND/OR
operations)
- 1 kB FIFO
Offset
±80 mg
TCO
±1 mg/K
Interface
SPI & I²C & 2 Interrupt pins
Supply voltage
1.71 V up to 3.6 V
Package
12 pin LGA 2x2x0.95 m³
Bosch Sensortec
BMA400
Ultra-low power, triaxial accelerometer
BMA400 TARGET APPLICATIONS
IoT and smart home applications (e.g. indoor climate
systems, security systems)
Activity tracking and step counting in wearable devices
(e.g. fitness bands, smart and regular watches, hearables)
Industrial applications (e.g. predictive maintenance,
package tracking)
Power management of consumer end-devices based on
motion
Bosch Sensortec | BMA400
Data & Specification are preliminary and subject to change without notice | | Bosch Sensortec GmbH reserves all
rights in the event of industrial property rights. We reserve all rights of disposal such as copying and passing on to third
parties. BOSCH and the symbols are registered trademarks of Robert Bosch GmbH, Germany.
2 | 2
Doc.-Number: BST-BMA400-FL000-00 / Version_1.0_122017
TECHNICAL SPECIFICATIONS
Pin configuration
Pin
Name
Description
1
SDO
Serial data output in SPI
Address select in I²C mode
2
SDX
SDA serial data I/O in I²C
SDI serial data input in SPI 4W
SDA serial data I/O in SPI 3W
3
VDDIO
Digital I/O supply voltage
(1.2 V … 3.6 V)
4
NC
Do not connect
5
INT1
Interrupt output 1 (default)
6
INT2
Interrupt output 2 (default)
7
VDD
Power supply for analog & digital
domain (1.62 V … 3.6 V)
8
GNDIO
Ground for I/O
9
GND
Ground for digital & analog
10
CSB
Chip select for SPI mode
11
NC
Do not connect
12
SCX
SCK for SPI serial clock
SCL for I²C serial clock
SENSOR OPERATION
1) Standard data polling mode: Acceleration data is directly read-
out via the sensor’s digital interface and computed by a system
μController or an application processor. Down to 3.2 µA the
acceleration data on the interface is always continuously
measured and has a defined selectable bandwidth. An
integrated FIFO with 1 kB of size as well as auto wake-up and
auto ultra-low power can be used optionally to reduce the overall
system current consumption.
2) Plug ’n’ play embedded functionality: Acceleration data is
computed already within the BMA400. The embedded features
of the sensor can trigger an interrupt at certain selectable events
which can be mapped to the selectable interrupt pins. In addition
to the electrical interrupt, the status of the events and the
counted steps are stored in the register map and can be read
out easily.
Embedded features:
Step detector / Step counter
Activity recognition: standing still, walking running
Activity change (detects change of unspecific periodic
activities)
Orientation
Tab/double tap
General interrupt 1 und 2: programmable by threshold, timing,
axes and logical AND/OR functionality.
Feature parameters can be configured by the designer and thus
perfectly support the adoption to the required use case and
system design.
SYSTEM COMPATIBILITY
The BMA400 has been designed for best possible fit into
modern wearable and IoT devices which are either non-
chargeable or chargeable devices that require a long battery
lifetime. Besides the lowest current consumption and superior
performance, the BMA400 has very wide ranges for VDD and
VDDIO supply voltages. The performance and the current
consumption are stable over the whole voltage supply range.
The BMA400 features I2C and SPI (3-wire/4-wire) digital, serial
interfaces. The availability of data timestamping enables the
synchronization of the acceleration data with other sensors
connected to the same µController or application processor. This
reduces the complexity of sensor data fusion and additionally
improves its precision. BMA400 is designed for plug ‘n’ play
functionality and ease-of-use in various system designs which
require ultra-low current consumption on both sensor and
system level.
Headquarters
Bosch Sensortec GmbH
Gerhard-Kindler-Strasse 9
72770 Reutlingen · Germany
Telephone +49 7121 3535 900
Fax +49 7121 3535 909
www.bosch-sensortec.com
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