Datasheet

Data Sheet
BMA456
Page 18
BST-BMA456-DS000-01 | Version 1.1 | October 2017 Bosch Sensortec
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BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.
Note: Specifications within this document are subject to change without notice.
4.3. Power Modes
The power state of the BMA456 is controlled through the registers PWR_CONF and PWR_CTRL. The
Register PWR_CTRL enables and disables the accelerometer and the auxiliary sensor. The Register
PWR_CONF controls which power state the sensors enter if they are enabled or disabled in the
Register PWR_CTRL. The power state impacts the behavior of the sensor with respect to start-up
time, available functions, etc. but not the sensor data quality. The sensor data quality is controlled in
the Registers ACC_CONF.
In all global power configurations both register contents and FIFO contents are retained.
Low Power Mode: This power configuration aggressively reduces power of the device as much as
possible. The low power mode configuration is activated through enabling
PWR_CONF.adv_power_save=0b1 and disabling ACC_CONF.acc_perf_mode=0b0. In this
configuration these externally user visible features may not be available:
 Register writes need an inter-write-delay of at least 1000 us.
 The sensors log data into the FIFO in performance and low power mode. When the FIFO
watermark interrupt is active, the FIFO is accessible for reading in low power mode until a
burst read operation on Register FIFO_DATA completes when
PWR_CONF.fifo_self_wakeup=0b1. When PWR_CONF.fifo_self_wakeup=0b0, the user
needs to disable advanced power save mode (PWR_CONF.adv_power_save=0b0) before
reading the FIFO and wait for 250 µs.
 To read out FIFO data w/o a FIFO watermark interrupt, the advanced power save
configuration needs to be disabled (PWR_CONF.adv_power_save=0b0)
The table below shows a few examples with the optimal power configurations
Usecase
ACC_CONF.acc_perf_mod e
PWR_CONF.adv_power_sa ve
PWR_CTRL.acc_en
Power c
onsumption
Configuration mode
x
0
x
tbd
Suspend (lowest power mode)
x
1
0
suspend power
Performance mode accel
1
x
1
accel power
Low power mode
0
1
1
Depends on ACC_CONF
The PWR_CTRL register is used to enable and disable sensors. Per default, all sensors are disabled.
Acceleration sensor must be enabled by setting PWR_CTRL.acc_en=0b1.