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Accelerometers
MEMS inertial sensor: 2-axis - +/-2g ultracompact linear accelerometer
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Last Updated: 27/10/2008
Pages: 17
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LIS2L02AL
MEMS INERTIAL SENSOR: 2-axis - +/-2g ultracompact linear accelerometer
Features
2.4V to 5.25V single supply operation Low power consumption
2g full-scale
0.3mg resolution over 100Hz bandwidth Embedded self test Output voltage, offset and sensitivity ratiometric to the supply voltage High shock survivability ECOPACK Lead-free compliant (see Section 6) LGA-8
to design a dedicated circuit which is trimmed to better match the sensing element characteristics. The LIS2L02AL has a full scale of 2g and it is capable of measuring accelerations over a bandwidth of 2.0 kHz for all axes. The device bandwidth may be reduced by using external capacitances. A self-test capability allows to check the mechanical and electrical signal path of the sensor. The LIS2L02AL is available in plastic SMD package and it is guaranteed to operate over an extended temperature range of -40C to +85C. The LIS2L02AL belongs to a family of products suitable for a variety of applications: Mobile terminals Gaming and Virtual Reality input devices Free-fall detection for data protection Antitheft systems and Inertial Navigation Appliance and Robotics.
Description
The LIS2L02AL is a low-power 2-axis linear capacitive accelerometer that 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. The sensing element, capable of detecting the acceleration, is manufactured using a dedicated process developed by ST to produce inertial sensors and actuators in silicon. The IC interface is manufactured using a standard CMOS process that allows high level of integration
Order codes
Part number LIS2L02AL LIS2L02ALTR Temp range, C -40C to +85C -40C to +85C Package LGA-8 LGA-8 Packing Tray Tape & Reel
May 2006
Rev 2
1/17
www.st.com 17
Contents
LIS2L02AL
Contents
1 Block diagram & pins description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 1.2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Mechanical and electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 2.2 2.3 2.4 Mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3
Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1 3.2 3.3 Sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 IC Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Factor y calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4
Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1 4.2 Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Output response vs. orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1 5.2 5.3 Mechanical characteristics at 25C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Mechanical characteristics derived from measurement in the -40C to +85C temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Electrical characteristics at 25C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6 7
Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2/17
LIS2L02AL
Block diagram & pins description
1
1.1
Block diagram & pins description
Block diagram
Figure 1. Block diagram
X+ Y+
CHARGE AMPLIFIER
S/H
Routx Voutx
a
YX-
MUX
DEMUX
Routy Vouty S/H
SELF TEST
REFERENCE
TRIMMING CIRCUIT
CLOCK
1.2
Pin description
Figure 2. Pin connection
LIS2L02AL
Vdd
X 1
Voutx Vouty ST NC GND
Y
Reserved
DIRECTION OF THE DETECTABLE ACCELERATIONS
Reserved BOTTOM VIEW
3/17
Block diagram & pins description Table 1.
Pin # 1 2 3 4 5 6 7 8
LIS2L02AL
Pin description
Pin Name ST NC GND Reserved Reserved Vouty Voutx Vdd Function Self Test (Logic 0: normal mode; Logic 1: Self-test) Not connected 0V supply Leave unconnected Leave unconnected Output Voltage Y channel Output Voltage X channel Power supply
4/17
LIS2L02AL
Mechanical and electrical specifications
2
2.1
Table 2.
Mechanical and electrical specifications
Mechanical characteristics
Mechanical characteristics(1) (Temperature range -40C to +85C) All the parameters are specified @ Vdd =3.3V, T = 25C unless otherwise noted
Parameter Acceleration Range(3) Sensitivity(4) Sensitivity Change Vs Temperature Zero-g Level(4) Zero-g level Change Vs Temperature Non Linearity(5) Full-scale = 2g Delta from +25C T = 25C Delta from +25C Best fit straight line Full-scale = 2g X, Y axis Vdd/2-6% Test Condition Min. 1.8 Vdd/510% Typ.(2) 2.0 Vdd/5 0.01 Vdd/2 0.2 Vdd/2+6% Vdd/5+10% Max. Unit g V/g %/C V mg/C
Symbol Ar So SoDr Voff OffDr
NL
0.3 2
1.5 4
% % g/
Hz
CrossAx Cross-Axis(6) An Acceleration Noise Density Vdd=3.3V; Full-scale = 2g T = 25C Vdd=3.3V Full-scale = 2g X axis T = 25C Vdd=3.3V Full-scale = 2g Y axis
30
-20
-50
-100
mV
Vt
Self test Output Voltage Change(7),(8)
20
50
100
mV
Fres Top Wh
Sensing Element all axes Resonance Frequency(9) Operating Temperature Range Product Weight
2.0 -40 0.08 +85
kHz C gram
1. The product is factory calibrated at 3.3V. The device can be powered from 2.4V to 5.25V. Voff, So and Vt parameters will vary with supply voltage. 2. Typical specifications are not guaranteed 3. Guaranteed by wafer level test and measurement of initial offset and sensitivity 4. Zero-g level and sensitivity are essentially ratiometric to supply voltage 5. Guaranteed by design 6. Contribution to the measuring output of the inclination/acceleration along any perpendicular axis 7. Self test "output voltage change" is defined as Vout(Vst=Logic1)-Vout(Vst=Logic0) 8. Self test "output voltage change" varies cubically with supply voltage 9. Minimum resonance frequency Fres=2.0KHz. Sensor bandwidth=1/(2**110k*Cload) with Cload>1nF.
5/17
Mechanical and electrical specifications
LIS2L02AL
2.2
Table 3.
Electrical characteristics
Electrical characteristics(1) (Temperature range -40C to +85C) All the parameters are specified @ Vdd =3.3V, T=25C unless otherwise noted
Parameter Supply Voltage Supply Current Self Test Input Logic 1 level Rout Output Impedance Capacitive Load Drive(3) Operating Temperature Range 0.7*Vdd 80 1 -40 +85 110 Vdd 140 V k nF C mean value Logic 0 level Vst 0 Test Condition Min. 2.4 Typ.(2) 3.3 0.85 Max. 5.25 1.5 0.3*Vdd Unit V mA V
Symbol Vdd Idd
Cload Top
1. The product is factory calibrated at 3.3V 2. Typical specifications are not guaranteed 3. Minimum resonance frequency Fres=2.0kHz. Sensor bandwidth=1/(2**110k*Cload) with Cload>1nF
6/17
LIS2L02AL
Mechanical and electrical specifications
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.
Symbol Vdd Vin APOW Supply voltage Input Voltage on Any Control pin (ST) Acceleration (Any axis, Powered, Vdd=3.3V) 10000g for 0.1 ms 3000g for 0.5 ms AUNP TSTG Acceleration (Any axis, Not powered) 10000g for 0.1 ms Storage Temperature Range -40 to +125 2kV HBM ESD Electrostatic Discharge Protection 200V MM 1500V CDM C
Absolute maximum ratings
Ratings Maximum Value -0.3 to 7 -0.3 to Vdd +0.3 3000g for 0.5 ms Unit V V
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
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.
7/17
Mechanical and electrical specifications
LIS2L02AL
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.
8/17
LIS2L02AL
Functionality
3
Functionality
The LIS2L02AL is a high performance, low-power, analog output 2-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 two different S&Hs, one for each channel and made available to the outside. The low noise input amplifier operates at 200 kHz while the two 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.
9/17
Application hints
LIS2L02AL
4
Application hints
Figure 3. LIS2L02AL Electrical connection
Vdd 10F GND 100nF GND
ST
Optional Vout X
X 1
LIS2L02AL (top view)
GND
Cload x
Optional Vout Y Cload y
Y
DIRECTION OF THE DETECTABLE ACCELERATIONS
Digital signals
Power supply decoupling capacitors (100nF ceramic or polyester + 10F Aluminum) should be placed as near as possible to the device (common design practice). The LIS2L02AL allows to band limit Voutx and Vouty through the use of external capacitors. The re-commended frequency range spans from DC up to 2.0KHz. In particular, capacitors must be added at output pins to implement low-pass filtering for antialiasing and noise reduction. The equation for the cut-off frequency (ft) of the external filters is:
1 f t = ------------------------------------------------------------2 R o u t C l o a d ( x, y )
Taking in account that the internal filtering resistor (Rout) has a nominal value equal to 110k, the equation for the external filter cut-off frequency may be simplified as follows:
1.45 F f t = ------------------------------ [ H z ] C l o a d ( x, y )
The tolerance of the internal resistor can vary typically of 20% within its nominal value of 110k; thus the cut-off frequency will vary accordingly. A minimum capacitance of 1nF for Cload(x, y) is required in any case. Table 5.
.
Filter capacitor selection, Cload (x,y)
Cut-off frequency 1 Hz 10 Hz 20 Hz 50 Hz 100 Hz 200 Hz 500 Hz Capacitor value 1500 nF 150 nF 68 nF 30 nF 15 nF 6.8 nF 3 nF
10/17
LIS2L02AL
Application hints
4.1
Soldering information
The LGA-8 package is compliant with the ECOPACK,RoHs and "Green" standard. It is qualified for soldering heat resistance according to JEDEC J-STD-020C. Pin 1 indicator is electrically connected to ST pin. Leave pin 1 indicator unconnected during soldering. Land pattern and soldering recommendations are available upon request.
4.2
Output response vs. orientation
Figure 4. Output response vs. orientation
X=1.65V(0g) Y=0.99V (-1g)
X=0.99V (-1g) Y=1.65V (0g)
TOP VIEW
X=2.31V (+1g) Y=1.65V (0g)
X=1.65V (0g) Y=1.65V (0g) X=1.65V(0g) Y=2.31V (+1g) Earth's Surface
Figure 4 shows LIS2L02AL Output Response vs Orientation at Vdd=3.3V
11/17
Typical performance characteristics
LIS2L02AL
5
5.1
Figure 5.
Typical performance characteristics
Mechanical characteristics at 25C
x-axis Zero-g level at 3.3V Figure 6. y-axis Zero-g level at 3.3V
25
25
20 Percent of parts (%) Percent of parts (%)
20
15
15
10
10
5
5
0 1.55
1.6
1.65 Zero-g Level (V)
1.7
1.75
0 1.55
1.6
1.65 Zero-g Level (V)
1.7
1.75
Figure 7.
x-axis sensitivity at 3.3V
Figure 8.
y-axis sensitivity at 3.3V
25
25
20 Percent of parts (%)
Percent of parts (%)
20
15
15
10
10
5
5
0 0.62
0.63
0.64
0.65 0.66 0.67 Sensitivity (V/g)
0.68
0.69
0.7
0 0.62
0.63
0.64
0.65 0.66 0.67 Sensitivity (V/g)
0.68
0.69
0.7
12/17
LIS2L02AL
Typical performance characteristics
5.2
Figure 9.
Mechanical characteristics derived from measurement in the -40C to +85C temperature range
x-axis Zero-g level change Vs temperature Figure 10. y-axis Zero-g level change Vs temperature
30
35 30 25 20 15 10 5 0
25 Percent of parts (%)
Percent of parts (%)
20
15
10
5
-0.4
-0.2 0 0.2 Zero-g level change (mg/deg. C)
0.4
0.6
0
-0.4
-0.2 0 0.2 0-g level change (mg/deg. C)
0.4
0.6
Figure 11. x-axis sensitivity change Vs temperature
30
Figure 12. y-axis sensitivity change Vs temperature
40 35
25 30 Percent of parts (%) 20 Percent of parts (%) 25 20 15 10 5 5 0 -0.05 -0.04 -0.03 -0.02 -0.01 0 0.01 Sensitivity Change (%/deg. C)
15
10
0 -0.05 -0.04 -0.03 -0.02 -0.01 0 0.01 Sensitivity Change(%/deg. C)
0.02
0.03
0.02
0.03
13/17
Typical performance characteristics
LIS2L02AL
5.3
Electrical characteristics at 25C
Figure 14. Current consumption at 3.3V
Figure 13. Noise density at 3.3V (x,y axis)
35 30 25 20 15 10 5
20 18 16
Percent of parts (%)
Percent of parts (%) 20 22 24 26 28 Noise density (ug/sqrt(Hz)) 30 32
14 12 10 8 6 4 2
0 18
0 0.4
0.6
0.8 1 current consumption (mA)
1.2
1.4
14/17
LIS2L02AL
Package Information
6
Package Information
In order to meet environmental requirements, ST offers these devices in ECOPACK packages. These packages have a Lead-free second level interconnect. The category of second Level Interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com. Figure 15. LGA-8 Mechanical Data & Package Dimensions
DIM. A1 A2 A3 D1 E1 L L1 M M1 N N1 N2 P1 P2 T1 T2 R h k j 0.615 1.200 0.150 0.050 0.100 1.300 0.740 0.875 0.180 4.850 4.850 0.220 5.000 5.000 1.270 2.540 1.225 0.900 2.000 1.225 1.170 1.350 0.790 1.170 0.640 mm MIN. 1.460 TYP. 1.520 MAX. MIN. inch TYP. MAX.
1.600 0.0574 0.0598 0.0629 1.330 0.260 5.150 5.150 0.0523 0.007 0.0086 0.0102 0.190 0.1968 0.2027 0.190 0.1968 0.2027 0.05 0.1 0.0482 0.925 0.0344 0.0354 0.0364 0.0787 0.0482 0.046 1.400 0.0511 0.0531 0.0551 0.840 0.0291 0.0311 0.033 0.046 0.665 0.0242 0.0251 0.0261 1.600 0.0472 0.0059 0.0019 0.0039 0.0629
OUTLINE AND MECHANICAL DATA
LGA8 (5x5x1.6mm) Land Grid Array Package
E1 A
A3 K C T1
E M M1
K (4x)
8 D D1 R L T2 == N 7 L1 6 5 4 KD 1 2 3 N2 N1 A2 A1 P1 h CA B seating plane DETAIL A K Detail A h CAB P2 D
KE
B
E
SOLDER MASK OPENING CAB
METAL PAD
j
j
CAB
7669231 C
15/17
Revision history
LIS2L02AL
7
Revision history
Table 6.
Date 26-Sep-2005 03-May-2006
Document revision history
Revision 1 2 Initial release. Corrected typo errors. Applied new corporate template layout. Changes
16/17
LIS2L02AL
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