LIS331DLH STMicroelectronics, LIS331DLH Datasheet - Page 14

• Manufacturer Part Number: LIS331DLH
• Description: Board Mount Accelerometers DGTL OUTPT MTN SEN MEMS ULTRA LO PWR
• Manufacturer: STMicroelectronics

Specifications of LIS331DLH

• Sensing Axis: X, Y, Z
• Acceleration: 2 g, 4 g, 8 g
• Digital Output - Number Of Bits: 16 bit
• Supply Voltage (max): 3.6 V
• Supply Voltage (min): 2.16 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Digital Output - Bus Interface: I2C, SPI
• Shutdown: Yes
• Package / Case: LGA-16
• Output Type: Digital
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Mechanical and electrical specifications
2.5
2.5.1
2.5.2
2.5.3
2.5.4
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Terminology
Sensitivity
Sensitivity describes the gain of the sensor and can be determined e.g. 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.
Zero-g level
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 in X axis and 0 g in 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 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 “Zero-g level change vs. temperature”. The Zero-g level tolerance (TyOff) describes the
standard deviation of the range of Zero-g levels of a population of sensors.
Self-test
Self-test allows to check the sensor functionality without moving it. The self-test function is
off when the self-test bit (ST) of CTRL_REG4 (control register 4) is programmed to ‘0‘.
When the self-test bit of CTRL_REG4 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 inside
Table
within the defined specifications.
Sleep to wake-up
The “sleep to wake-up” function, in conjunction with low-power mode, allows to further
reduce the system power consumption and develop new smart applications.
LIS331DLH may be set in a low-power operating mode, characterized by lower date rates
refreshments. In this way the device, even if sleeping, keep on sensing acceleration and
generating interrupt requests.
When the “sleep to wake-up” function is activated, LIS331DLH is able to automatically
wake-up as soon as the interrupt event has been detected, increasing the output data rate
and bandwidth.
With this feature the system may be efficiently switched from low-power mode to full-
performance depending on user-selectable positioning and acceleration events, thus
ensuring power saving and flexibility.
3, then the sensor is working properly and the parameters of the interface chip are
Doc ID 15094 Rev 3
LIS331DLH