2 Mechanical and Electrical Specifications

LIS2L02AL

8/17

CD00068420

Self Test allows to test the mechanical and electric part of the sensor, allowing the seismic

mass to be moved by means of an electrostatic test-force. The Self Test function is off when the

ST pin is connected to GND. When the ST pin is tied at Vdd an actuation force is applied to the

sensor, simulating a definite input acceleration. In this case the sensor outputs will exhibit a

voltage change in their DC levels which is related to the selected full scale and depending on

the Supply Voltage through the device sensitivity. When ST 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 2, than the sensor is working properly and the parameters of the interface chip are

within the defined specification.

Output impedance describes the resistor inside the output stage of each channel. This

resistor is part of a filter consisting of an external capacitor of at least 723pF and the internal

resistor. Due to the high resistor level only small, inexpensive external capacitors are needed to

generate low corner frequencies. When interfacing with an ADC it is important to use high input

impedance input circuitries to avoid measurement errors. Note that the minimum load

capacitance forms a corner frequency beyond the resonance frequency of the sensor. For a flat

frequency response a corner frequency well below the resonance frequency is recommended.

In general the smallest possible bandwidth for an particular application should be chosen to get

the best results.