Datasheet

Terminology and functionality LIS2DH12
16/53 DocID025056 Rev 6
3 Terminology and functionality
3.1 Terminology
3.1.1 Sensitivity
Sensitivity describes the gain of the sensor and can be determined 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 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 will measure 0 g for the X-axis and 0 g for the Y-axis whereas the Z-axis will
measure 1 g. The output is ideally in the middle of the dynamic range of the sensor (content
of OUT registers 00h, data expressed as two’s complement number). A deviation from the
ideal value in this case is called zero-g offset. Offset is to some extent a result of stress to
the MEMS sensor and therefore the offset can slightly change after mounting the sensor on
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
The LIS2DH12 provides three different operating modes: high-resolution mode, normal
mode and low-power mode.
The table below summarizes how to select the different operating modes.
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)
(1)
0 1 ODR/9 7/ODR 1
Not allowed 1 1 -- -- --
1. By design, when the device from high-resolution configuration (HR) is set to power-down mode (PD), it is recommended to
read register REFERENCE (26h) for a complete reset of the filtering block before switching to normal/high-performance
mode again.