Datasheet

Datasheet
BMM150 Geomagnetic Sensor
Page 11
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.
4. Functional description
BMM150 is a triaxial standalone geomagnetic sensor (Sensing element and ASIC) in chip scale
wafer level package and can be operated via I2C or SPI as a slave device.
4.1 Power management
The BMM150 has two distinct power supply pins:
• V
DD
is the main power supply for all internal analog and digital functional blocks;
• V
DDIO
is a separate power supply pin, used for the supply of the digital interface as well as the
digital logic.
The device can be completely switched off (V
DD
= 0V) while keeping the V
DDIO
supply on (V
DDIO
>
0V) or vice versa.
It is absolutely prohibited to keep any interface at a logical high level when V
DDIO
is switched off.
Such a configuration will permanently damage the device (i.e. if V
DDIO
= 0  [SDI & SDO & SCK
& CSB] ≠ high).
The device contains a power on reset (POR) generator. It resets the logic part and the register
values of the concerned ASIC after powering-on V
DD
and V
DDIO
. Please note, that all application
specific settings which are not equal to the default settings (refer to register maps in chapter
5.2), must be re-set to its designated values after POR.
In case the I²C interface is used, a direct electrical connection between V
DDIO
supply and the PS
pin is recommended in order to ensure reliable protocol selection.
4.2 Power modes
The BMM150 features configurable power modes. The BMM150 magnetometer part has four
power modes:In the following chapters, power modes are described.
4.2.1 Power off mode
In Power off mode, V
DD
and/or V
DDIO
are unpowered and the device does not operate. When
only one of V
DD
or V
DDIO
is supplied, the magnetic sensor will still be in Power off mode. Power
on reset is performed after both V
DD
and V
DDIO
raised above their detection thresholds.
4.2.2 Suspend mode
Suspend mode is the default power mode of BMM150 after the chip is powered. When V
DD
and
V
DDIO
are turned on the POR (power on reset) circuits operate and the device’s registers are
initialized. After POR becomes inactive, a start up sequence is executed. In this sequence NVM
content is downloaded to shadow registers located in the device core. After the start up
sequence the device is put in the Suspend mode. In this mode only registers which store power
control bit information and SPI3 wire enable can be accessed by the user. No other registers
can be accessed in Suspend mode. All registers lose their content, except the control register
(0x4B). In particular, in this mode a Chip ID read (register 0x40) returns “0x00” (I²C) or high-Z
(SPI).