LIS3L06AL Datasheet LIS3L06AL | P7-P9

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LIS3L06AL Mechanical and Electrical Specifications

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2.3 Absolute maximum ratings

Stresses above those listed as “absolute maximum ratings” may cause permanent damage

to the device. This is a stress rating only and functional operation of the device under these

conditions is not implied. Exposure to maximum rating conditions for extended periods may

affect device reliability.

2.4 Terminology

Sensitivity describes the gain of the sensor and can be determined by applying 1g

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, note the output value, rotate the

sensor by 180 degrees (point to the sky) and note the output value again thus applying ±1g

acceleration to the sensor. Subtracting the larger output value from the smaller one and

dividing the result by 2 will give the actual sensitivity of the sensor. This value changes very

little over temperature (see sensitivity change vs. temperature) and also very little over time.

The Sensitivity Tolerance describes the range of Sensitivities of a large population of

sensors.

Zero-g level describes the actual output signal if there is no acceleration present. A sensor

in a steady state on a horizontal surface will measure 0g in X axis and 0g in Y axis. The

output is ideally for a 3.3V powered sensor Vdd/2 = 1650mV. A deviation from ideal 0-g level

(1650mV in this case) is called Zero-g offset. Offset of precise MEMS sensors is to some

extend a result of stress to the 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 of an individual sensor is very stable over lifetime. The Zero-g level

tolerance describes the range of Zero-g levels of a population of sensors.

Table 4. Absolute maximum ratings

Symbol Ratings Maximum Value Unit

Vdd Supply voltage -0.3 to 7 V

Vin Input Voltage on Any Control pin (ST, FS) -0.3 to Vdd +0.3 V

POW

Acceleration (Any axis, Powered, Vdd=3.3V)

3000g for 0.5 ms

10000g for 0.1 ms

UNP

Acceleration (Any axis, Not powered)

3000g for 0.5 ms

10000g for 0.1 ms

STG

Storage Temperature Range -40 to +125 °C

ESD Electrostatic Discharge Protection

2kV HBM

200V MM

1500V CDM

This is a Mechanical Shock sensitive device, improper handling can cause permanent

damages to the part

This is an ESD sensitive device, improper handling can cause permanent damages to

the part

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Mechanical and Electrical Specifications LIS3L06AL

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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 1nF 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.

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LIS3L06AL Functionality

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3 Functionality

The LIS3L06AL is a high performance, low-power, analog output 3-axis linear

accelerometer packaged in a LGA package. The complete device includes a sensing

element and an IC interface able to take the information from the sensing element and to

provide an analog signal to the external world.

3.1 Sensing element

A proprietary process is used to create a surface micro-machined accelerometer. The

technology allows to carry out suspended silicon structures which are attached to the

substrate in a few points called anchors and are free to move in the direction of the sensed

acceleration. To be compatible with the traditional packaging techniques a cap is placed on

top of the sensing element to avoid blocking the moving parts during the moulding phase of

the plastic encapsulation.

When an acceleration is applied to the sensor the proof mass displaces from its nominal

position, causing an imbalance in the capacitive half-bridge. This imbalance is measured

using charge integration in response to a voltage pulse applied to the sense capacitor.

At steady state the nominal value of the capacitors are few pF and when an acceleration is

applied the maximum variation of the capacitive load is up to 100fF.

3.2 IC Interface

In order to increase robustness and immunity against external disturbances the complete

signal processing chain uses a fully differential structure. The final stage converts the

differential signal into a single-ended one to be compatible with the external world.

The signals of the sensing element are multiplexed and fed into a low-noise capacitive

charge amplifier that implements a Correlated Double Sampling system (CDS) at its output

to cancel the offset and the 1/f noise. The output signal is de-multiplexed and transferred to

three different S&Hs, one for each channel and made available to the outside.

The low noise input amplifier operates at 200 kHz while the three S&Hs operate at a

sampling frequency of 66 kHz. This allows a large oversampling ratio, which leads to in-

band noise reduction and to an accurate output waveform.

All the analog parameters (Zero-g level, sensitivity and self-test) are ratiometric to the

supply voltage. Increasing or decreasing the supply voltage, the sensitivity and the offset will

increase or decrease almost linearly. The self test voltage change varies cubically with the

supply voltage.

3.3 Factory calibration

The IC interface is factory calibrated for sensitivity (So) and Zero-g level (Voff).

The trimming values are stored inside the device by a non volatile structure. Any time the

device is turned on, the trimming parameters are downloaded into the registers to be

employed during the normal operation. This allows the user to employ the device without

further calibration.

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LIS3L06AL

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STMicroelectronics

Description:

ACCELEROMETER 2-6G ANALOG 8LGA

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