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