LSM303DLH Datasheet, PDF (18/47 Pages) STMicroelectronics – Sensor module: 3-axis accelerometer and 3-axis magnetometer

Functionality
5
Functionality
LSM303DLH
The LSM303DLH is a system-in-package featuring a 3D digital linear acceleration and 3D
digital magnetic field detection sensor.
The system includes specific sensing elements and an IC interfaces capable of measuring
both the linear acceleration and magnetic field applied to it, and to provide a signal to the
external world through an I²C serial interface with separated digital ouput.
The sensing system is manufactured using specialized micromachining processes, while
the IC interfaces are realized using a CMOS technology that allows the design of a
dedicated circuit which is trimmed to better match the sensing element characteristics.
The LSM303DLH features two data-ready signals (RDY) which indicate when a new set of
measured acceleration data and magnetic data are available, thus simplifying data
synchronization in the digital system that uses the device.
The LSM303DLH may also be configured to generate an inertial wakeup and free-fall
interrupt signal according to a programmed acceleration event along the enabled axes. Both
free-fall and wakeup can be used simultaneously on two different accelerometer interrupts.
5.1
Factory calibration
The IC interface is factory calibrated for linear acceleration sensitivity (LA_So), and linear
acceleration Zero-g level (LA_TyOff).
The trimming values are stored inside the device in non-volatile memory. When the device is
turned on, the trimming parameters are downloaded into the registers to be used during
normal operation. This allows the use of the device without further calibration.
5.2
Linear acceleration self-test operation
Self-test allows the checking of sensor functionality without moving it. The self-test function
is off when the self-test bit (ST) of CTRL_REG4_A (control register 4) is programmed to ‘0‘.
When the self-test bit of CTRL_REG4_A is programmed to ‘1‘ an actuation force is applied
to the sensor, simulating a definite input acceleration. In this case the sensor outputs will
exhibit a change in their DC levels which are related to the selected full-scale through the
device sensitivity. When self-test is activated, the device output level is given by the
algebraic sum of the signals produced by the acceleration acting on the sensor and by the
electrostatic test-force. If the output signals change within the amplitude specified in
Table 3, then the sensor is working properly and the parameters of the interface chip are
within the defined specifications.
5.3
Magnetic self-test operation
To check the magnetic sensor for proper operation, a self-test feature is incorporated in
which the sensor offset straps are excited to create a nominal field strength (bias field) to be
measured. To implement this self-test, the least significant bits (MS1 and MS0) of
configuration register A are changed from 00 to 01 (0x12 or 0b000xxx01).
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Doc ID 16941 Rev 1