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:

µs

nZ

µs

nXY

µs

f

ODR

980

500

145

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