Datasheet

Mechanical and electrical specifications LIS2DH
18/49 Doc ID 022516 Rev 1
2.6.5 6D / 4D orientation detection
The LIS2DH include 6D / 4D orientation detection.
6D / 4D orientation recognition
In this configuration the interrupt is generated when the device is stable in a known
direction. In 4D configuration Z axis position detection is disable.
2.6.6 “Sleep to wake” and “Return to sleep”
The LIS2DH can be programmed to automatically switch to Low power mode upon
recognition of a determined event.
Once the event condition is over, the device returns back to the preset Normal or High
resolution mode.
To enable this function the desired threshold value must be stored inside Act_THS(3Eh)
registers while the duration value written inside Act_DUR(3Fh) registers.
When acceleration module becomes lower than the treshold value, the device automatically
switches to Low power mode (10Hz ODR).
During this condition, ODRx bits and LPen bit inside CTRL_REG1 (20h) and HR bit in
CTRL_REG3 (22h) are not considered.
As soon as the acceleration goes back over the threshold, the systems restores the
operating mode and ODRs as for CTRL_REG1 (20h) and CTRL_REG3 (22h) settings.
2.7 Sensing element
A proprietary process is used to create a surface micro-machined accelerometer. The
technology allows carring out suspended silicon structures which are attached to the
substrate in a few points called anchors and are free to move in the direction of the sensed
acceleration. To be compatible with the traditional packaging techniques a cap is placed on
top of the sensing element to avoid blocking the moving parts during the moulding phase of
the plastic encapsulation.
When an acceleration is applied to the sensor the proof mass displaces from its nominal
position, causing an imbalance in the capacitive half-bridge. This imbalance is measured
using charge integration in response to a voltage pulse applied to the capacitor.
At steady state the nominal value of the capacitors are few pF and when an acceleration is
applied the maximum variation of the capacitive load is in the fF range.
2.8 IC interface
The complete measurement chain is composed by a low-noise capacitive amplifier which
converts the capacitive unbalancing of the MEMS sensor into an analog voltage that is
finally available to the user by an analog-to-digital converter.
The acceleration data may be accessed through an I
2
C/SPI interface thus making the
device particularly suitable for direct interfacing with a microcontroller.
The LIS2DH features a data-ready signal (RDY) which indicates when a new set of
measured acceleration data is available thus simplifying data synchronization in the digital
system that uses the device.