Datasheet

Datasheet
BMM150 Geomagnetic Sensor
Page 12
BST-BMM150-DS001-01 | Revision 1.0 | April 2013 Bosch Sensortec
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Note: Specifications within this document are subject to change without notice.
4.2.3 Sleep mode
The user puts device from suspend into Sleep mode by setting the Power bit to “1”, or from
active modes (normal or forced) by setting OpMode bits to “11”. In this state the user has full
access to the device registers. In particular, the Chip ID can be read. Setting the power control
bit to “0” (register 0x4B bit0) will bring the device back into Suspend mode. From the Sleep
mode the user can put the device back into Suspend mode or into Active mode.
4.2.4 Active mode
The device can switch into Active mode from Sleep mode by setting OpMode bits (register
0x4C). In this mode the magnetic field measurements are performed and all registers are
accessible.
In active mode, two operation modes can be distinguished:
 Normal mode: selected channels are periodically measured according to settings set in
user registers. After measurements are completed, output data is put into data registers
and the device waits for the next measurement period, which is set by programmed
output data rate (ODR). From normal mode, the user can return to sleep mode by setting
OpMode to “11” or by performing a soft reset (see chapter 5.6). Suspend mode can be
entered by setting power control bit to “0”.
 Forced mode (single measurement): When set by the host, the selected channels are
measured according to settings programmed in user registers. After measurements are
completed, output data is put into data registers, OpMode register value returns to “11”
and the device returns to sleep mode. The forced mode is useful to achieve
synchronized operation between host microcontroller and BMM150. Also, different data
output rates from the ones selectable in normal mode can be achieved using forced
mode.
Figure 2: Magnetometer power mode transition diagram
In Active Mode and normal operation, in principle any desired balance between output noise
and active time (hence power consumption) can be adjusted by the repetition settings for x/y-
axis and z-axis and the output data rate ODR. The average power consumption depends on the
ratio of high current phase time (during data acquisition) and low current phase time (between
data acquisitions). Hence, the more repetitions are acquired to generate one magnetic field data