Datasheet

Datasheet
BMM150 Geomagnetic Sensor
Page 13
BST-BMM150-DS001-01 | Revision 1.0 | April 2013 Bosch Sensortec
© Bosch Sensortec GmbH reserves all rights even 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 symbol are registered trademarks of Robert Bosch GmbH, Germany.
Note: Specifications within this document are subject to change without notice.
point, the longer the active time ratio in one sample phase, and the higher the average current.
Thanks to longer internal averaging, the noise level of the output data reduces with increasing
number of repetitions.
By using forced mode, it is possible to trigger new measurements at any rate. The user can
therefore trigger measurements in a shorter interval than it takes for a measurement cycle to
complete. If a measurement cycle is not allowed to complete, the resulting data will not be
written into the data registers. To prevent this, the manually triggered measurement intervals
must not be shorter than the active measurement time which is a function of the selected
number of repetitions. The maximum selectable read-out frequency in forced mode can be
calculated as follows:
µsnZµsnXYµs
f
ODR
980500145
1
max,


Hereby nXY is the number of repetitions on X/Y-axis (not the register value) and nZ the number
of repetitions on Z-axis (not the register value) (see description of XY_REP and Z_REP
registers in chapter 5).
Although the repetition numbers for X/Y and Z axis and the ODR can be adjusted independently
and in a wide range, there are four recommended presets (High accuracy preset, Enhanced
regular preset, Regular preset, Low power preset) which reflect the most common usage
scenarios, i.e. required output accuracy at a given current consumption, of the BMM150.
The four presets consist of the below register configurations, which are automatically set by the
BMM150 API or driver provided by Bosch Sensortec when a preset is selected. Table 3 shows
the recommended presets and the resulting magnetic field output noise and current
consumption:
Table 3: Recommended presets for repetitions and output data rates:
Preset
Rep.
X/Y
nXY
Rep.
Z
nZ
recommended
ODR
[Hz]
Max
ODR in
forced
mode
fmax,OD
R
[Hz]
RMS Noise
x/y/z
[µT]
Average
current
consumption
at
recommended
ODR
[mA]
Low power
preset
3
3
10
>300
1.0/1.0/1.4
0.17
Regular
preset
9
15
10
100
0.6/0.6/0.6
0.5
Enhanced
regular preset
15
27
10
60
0.5/0.5/0.5
0.8
High accuracy
preset
47
83
20
20
0.3/0.3/0.3
4.9