BMA253
Data sheet
Page 15
In suspend mode the whole analog part is powered down. No data acquisition is performed.
While in suspend mode the latest acceleration data and the content of all configuration registers
are kept. Writing to and reading from registers is supported except from the (0x3E)
fifo_config_1, (0x30) fifo_config_0 and (0x3F) fifo_data register. It is possible to enter normal
mode by performing a softreset as described in chapter 4.8.
Suspend mode is entered (left) by writing ´1´ (´0´) to the (0x11) suspend bit after bit (0x12)
lowpower_mode has been set to ‘0’. Although write access to registers is supported at the full
interface clock speed (SCL or SCK), a waiting period must be inserted between two
consecutive write cycles (please refer also to section 7.2.1).
In standby mode the analog part is powered down, while the digital part remains largely
operational. No data acquisition is performed. Reading and writing registers is supported
without any restrictions. The latest acceleration data and the content of all configuration
registers are kept. Standby mode is entered (left) by writing ´1´ (´0´) to the (0x11) suspend bit
after bit (0x12) lowpower_mode has been set to ‘1’. It is also possible to enter normal mode by
performing a softreset as described in chapter 4.8.
In low-power mode 1, the device is periodically switching between a sleep phase and a wake-
up phase. The wake-up phase essentially corresponds to operation in normal mode with
complete power-up of the circuitry. The sleep phase essentially corresponds to operation in
suspend mode. Low-power mode is entered (left) by writing ´1´ (´0´) to the (0x11) lowpower_en
bit with bit (0x12) lowpower_mode set to ‘0’. Read access to registers is possible except from
the (0x3F) fifo_data register. However, unless the register access is synchronised with the
wake-up phase, the restrictions of the suspend mode apply.
Low-power mode 2 is very similar to low-power mode 1, but register access is possible at any
time without restrictions. It consumes more power than low-power mode 1. In low-power mode
2 the device is periodically switching between a sleep phase and a wake-up phase. The wake-
up phase essentially corresponds to operation in normal mode with complete power-up of the
circuitry. The sleep phase essentially corresponds to operation in standby mode. Low-power
mode is entered (left) by writing ´1´ (´0´) to the (0x11) lowpower_en bit with bit (0x12)
lowpower_mode set to ‘1’.
The timing behaviour of the low-power modes 1 and 2 depends on the setting of the (0x12)
sleeptimer_mode bit. When (0x12) sleeptimer_mode is set to ‘0’, the event-driven time-base
mode (EDT) is selected. In EDT the duration of the wake-up phase depends on the number of
samples required by the enabled interrupt engines. If an interrupt is detected, the device stays
in the wake-up phase as long as the interrupt condition endures (non-latched interrupt), or until
the latch time expires (temporary interrupt), or until the interrupt is reset (latched interrupt). If no
interrupt is detected, the device enters the sleep phase immediately after the required number
of acceleration samples have been taken and an active interface access cycle has ended. The
EDT mode is recommended for power-critical applications which do not use the FIFO. Also,
EDT mode is compatible with legacy BST sensors. Figure 3 shows the timing diagram for low-
power modes 1 and 2 when EDT is selected.
BST-BMA253-DS000-01 | Revision 1.0 | August 2015
Bosch Sensortec
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Note: Specifications within this document are subject to change without notice.
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