Datasheet
Terminology and functionality LIS3DH
16/54 DocID17530 Rev 2
3 Terminology and functionality
3.1 Terminology
3.1.1 Sensitivity
Sensitivity describes the gain of the sensor and can be determined, for example, by
applying 1 g acceleration to it. As the sensor can measure DC accelerations this can be
done easily by pointing the axis of interest towards the center of the Earth, noting the output
value, rotating the sensor by 180 degrees (pointing to the sky) and noting the output value
again. By doing so, ±1 g acceleration is applied to the sensor. Subtracting the larger output
value from the smaller one, and dividing the result by 2, leads to the actual sensitivity of the
sensor. This value changes very little over temperature and also time. The sensitivity
tolerance describes the range of sensitivities of a large population of sensors.
3.1.2 Zero-g level
The zero-g level offset (TyOff) describes the deviation of an actual output signal from the
ideal output signal if no acceleration is present. A sensor in a steady state on a horizontal
surface measures 0 g for the X-axis and 0 g for the Y-axis whereas the Z-axis measures 1 g.
The output is ideally in the middle of the dynamic range of the sensor (content of OUT
registers 00h, data expressed as 2’s complement number). A deviation from ideal value in
this case is called Zero-g offset. Offset is to some extent a result of stress to MEMS sensor
and therefore the offset can slightly change after mounting the sensor onto a printed circuit
board or exposing it to extensive mechanical stress. Offset changes little over temperature,
see Table 4 “Zero-g level change vs. temperature” (TCOff). The zero-g level tolerance
(TyOff) describes the standard deviation of the range of zero-g levels of a population of
sensors.
3.2 Functionality
3.2.1 High-resolution, normal mode, low-power mode
LIS3DH provides three different operating modes: high-resolution mode, normal mode and
low-power mode.
The table below summarizes how to select the operating mode.
Table 10. Operating mode selection
Operating mode
CTRL_REG1[3]
(LPen bit)
CTRL_REG4[3]
(HR bit)
BW [Hz]
Turn-on
time [ms]
So @ ±2g
[mg/digit]
Low-power mode
(8-bit data output)
1 0 ODR/2 1 16
Normal mode
(10-bit data output)
0 0 ODR/2 1.6 4
High-resolution mode
(12-bit data output)
0 1 ODR/9 7/ODR 1
Not allowed 1 1 -- -- --