LIS2L02AQ3TR Datasheet LIS2L02AQ3TR | P7-P9

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LIS2L02AQ3 2 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.

Table 4. Absolute maximum ratings

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.

Symbol Ratings Maximum Value Unit

Vdd Supply voltage -0.3 to 7 V

Vin Input Voltage on Any Control pin (FS, PD, ST) -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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2 Mechanical and Electrical Specifications LIS2L02AQ3

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Self Test allows to test the mechanical and electrical part of the sensor. By applying a digital

signal to the ST input pin an internal reference is switched to a certain area of the sensor and

creates a defined deflection of the moveable structure. The sensor will generate a defined

signal and the interface chip will perform the signal conditioning. If the output signal changes

with the specified amplitude than the sensor is working properly and the parameters of the

interface chip are within the defined specifications.

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 320pF 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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LIS2L02AQ3 3 Functionality

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3 Functionality

The LIS2L02AQ3 is a high performance, low-power, analog output 2-axis linear accelerometer

packaged in a QFN 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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LIS2L02AQ3TR

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Accelerometers MEMS INERTIAL snsr 2 axis

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