Mechanical and electrical specifications

LIS331AL

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over lifetime. The Zero-g level tolerance describes the range of Zero-g levels of a population

of sensors.

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 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 3, 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 2.5nF and the internal

resistor. Due to the 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 close to the resonance frequency of the sensor. In

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

the best results.