LIS344AL
MEMS inertial sensor 3-axis ultracompact linear accelerometer
Features
Single voltage supply operation
3.5g full-scale
Output voltage, offset and sensitivity are ratiometric to the supply voltage Factory trimmed device sensitivity and offset Embedded self test RoHS/ECOPACK compliant High shock survivability (10000g) The LIS344AL is capable of measuring accelerations over a maximum bandwidth of 2.0kHz. The device bandwidth may be reduced by using external capacitances. A self-test capability allows the user to check the functioning of the system. The LIS344AL is available in Land Grid Array package (LGA) and it is guarantee to operate over an extended temperature range of -40C to +85C. The LIS344AL belongs to a family of products suitable for a variety of applications: Mobile terminals Gaming and virtual reality input devices Antitheft systems and inertial navigation Appliance and robotics.
LGA 16 (4x4x1.5mm)
Description
The LIS344AL is an ultra compact consumer lowpower three-axis linear 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 CMOS process that allows high level of integration to design a dedicated circuit which is trimmed to better match the sensing element characteristics.
Table 1.
Device summary
Temp range, C -40C to +85C -40C to +85C Package LGA-16 LGA-16 Packing Tray Tape & Reel
Order code LIS344AL LIS344ALTR
December 2007
Rev 1
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Content
LIS344AL
Content
1 Block diagram and pins description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 1.2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2
Mechanical and electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 2.2 2.3 2.4 Mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3
Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1 3.2 3.3 Sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 IC Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Factor y calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4
Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1 4.2 Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Output response vs. orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5 6
Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
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LIS344AL
List of figures
List of figures
Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 LIS344AL electrical connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Output response vs. orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 LGA 16: mechanical data & package dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
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List of tables
LIS344AL
List of tables
Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Filter capacitor selection, Cload (x,y,z), . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
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LIS344AL
Block diagram and pins description
1
1.1
Block diagram and pins description
Block diagram
Figure 1. Block diagram
X+ Y+ Z+
CHARGE AMPLIFIER S/H
Routx
VoutX
a
ZYX-
Routy MUX DEMUX S/H
VoutY
Routz S/H
VoutZ
SELF TEST
REFERENCE
T R I M M I N G CIRCUIT
CLOCK
1.2
Pin description
Figure 2. Pin connection
Z
13
NC
Vdd
NC Res
16
Pin 1 Indicator
1
VoutX NC VoutY
Y
12
1
NC ST GND
X
NC
9 8 5
4
NC
VoutZ
GND
GND
GND
(TOP VIEW) DIRECTIONS OF THE DETECTABLE ACCELERATIONS
(BOTTOM VIEW)
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Block diagram and pins description Table 2.
Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
LIS344AL
Pin description
Pin name NC ST GND NC GND GND GND VoutZ NC VoutY NC VoutX NC Vdd Res NC Function Not connected Self Test (Logic 0: normal mode; Logic 1: Self-test mode) 0V supply Not connected 0V supply 0V supply 0V supply Output voltage Z channel Not connected Output voltage Y channel Not connected Output voltage X channel Not connected Power supply Connect to Vdd Not connected
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LIS344AL
Mechanical and electrical specifications
2
2.1
Mechanical and electrical specifications
Mechanical characteristics
All the parameters are specified @ Vdd =3.0 V, T = 25C unless otherwise noted
Table 3.
Symbol Ar So SoDr Voff OffDr NL CrossAx An
Mechanical characteristics(1)
Parameter Acceleration range(3) Sensitivity(5) Sensitivity change vs temperature Zero-g level(4) Delta from +25C T = 25C Vdd/2-15% 0.100*Vdd 10% Test condition Min. Typ.(2) 3.5 0.100*Vdd 0.01 Vdd/2 0.7 0.6 2 Vdd=3.0 V T = 25C Vdd=3.0 V X axis 275 Vdd/2+15% 0.100*Vdd+ 10% Max. Unit g V/g %/C V mg/C % FS % g/ H z
Zero-g level change vs Delta from +25C temperature Non linearity(5) Cross-axis(6) Acceleration noise density Best fit straight line
84
mV
Vt
T = 25C Self test output voltage Vdd=3.0 V change(7) Y axis T = 25C Vdd=3.0 V Z axis
84
mV
-84
mV
Fres Top Wh
Sensing element resonant frequency(8) Operating temperature range Product weight
X, Y, Z axis
2.0 -40 0.040 +85
KHz C gram
1. The product is factory calibrated at 3.0 V. The operational power supply range is from 2.7 V to 3.3 V. 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 at the calibration level 8%. 5. Guaranteed by design. 6. Contribution to the measuring output of an inclination/acceleration along any perpendicular axis. 7. "Self test output voltage change" is defined as Vout(Vst=Logic1)-Vout(Vst=Logic0). 8. Minimum resonance frequency Fres=2.0 KHz. Sensor bandwidth=1/(2**32 k*Cload), with Cload>2.5 nF.
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Mechanical and electrical specifications
LIS344AL
2.2
Electrical characteristics
All the parameters are specified @ Vdd =3.0 V, T=25C unless otherwise noted Table 4.
Symbol Vdd Idd Vst
Electrical characteristics(1)
Parameter Supply voltage Supply current Logic 0 level Self Test Input Logic 1 level 2.0 32 Vdd V K Output impedance of VoutX, VoutY, VoutZ Capacitive load drive(3) for VoutX, VoutY, VoutZ 0 Test condition Min. 2.7 Typ.(2) 3.0 0.69 0.8 Max. 3.3 Unit V mA V
Rout
Cload
2.5
nF
1. The product is factory calibrated at 3.0 V. 2. Typical specifications are not guaranteed. 3. Minimum resonance frequency Fres=2 KHz. Device bandwidth=1/(2**32 k*Cload), with Cload>2.5 nF.
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 5.
Symbol Vdd Vin APOW Supply voltage Input voltage on any control pin (ST) Acceleration (any axis, powered, Vdd=3.0 V) 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 2 (HBM) ESD Electrostatic discharge protection 1.5 (CDM) 200 (MM) C KV KV V
Absolute maximum ratings
Ratings Maximum value -0.3 to 6 -0.3 to Vdd +0.3 3000g for 0.5 ms Unit V V
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LIS344AL
Mechanical and electrical specifications
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 whereas the Z axis will measure 1g. The output is ideally for a 3.0V powered sensor Vdd/2 = 1500 mV. A deviation from ideal 0-g level (1500 mV 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. 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, then 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 2.5 nF 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.
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Functionality
LIS344AL
3
Functionality
The LIS344AL is an ultra compact low-power, analog output three-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 in fF range.
3.2
IC Interface
The complete signal processing uses a fully differential structure, while the final stage converts the differential signal into a single-ended one to be compatible with the external world. The first stage is a low-noise capacitive amplifier that implements a Correlated Double Sampling (CDS) at its output to cancel the offset and the 1/f noise. The produced signal is then sent to three different S&Hs, one for each channel, and made available to the outside. All the analog parameters (output offset voltage and sensitivity) are ratiometric to the voltage supply. Increasing or decreasing the voltage supply, the sensitivity and the offset will increase or decrease linearly. The feature provides the cancellation of the error related to the voltage supply along an analog to digital conversion chain.
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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LIS344AL
Application hints
4
Application hints
Figure 3. LIS344AL electrical connection
GND
100nF
GND
10F
Vdd
Z
1
Optional Pin 1 indicator
16 1
15
14
13 12
Cload X
ST
Vout x
Optional
2 3 4
LIS344AL
(top view)
11 10 9
Y
Vout y
Cload Y
X
( T O P VIEW) D I R E C T I O N S OF THE DETECTABLE ACCELERATIONS
5
6
7
8
Optional
GND
Cload Z
Vout z
Digital signals
Power supply decoupling capacitors (100 nF ceramic or polyester + 10 F Aluminum) should be placed as near as possible to the device (common design practice). The LIS344AL allows to band limit VoutX, VoutY and VoutZ through the use of external capacitors. The recommended frequency range spans from DC up to 2.0 kHz. In particular, capacitors are added at output VoutX, VoutY, VoutZ pins to implement low-pass filtering for antialiasing and noise reduction. The equation for the cut-off frequency (ft) of the external filters is in this case: 1 f t = -----------------------------------------------------------------------2 R o u t C l o a d ( x, y, z ) Taking into account that the internal filtering resistor (Rout) has a nominal value equal to 32 k the equation for the external filter cut-off frequency may be simplified as follows: , 5 F f t = -------------------------------------- [ H z ] C l o a d ( x, y, z ) The tolerance of the internal resistor can vary typically of 20% within its nominal value of 32 k; thus the cut-off frequency will vary accordingly. A minimum capacitance of 2.5 nF for Cload(x, y, z) is required.
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Application hints Table 6. Filter capacitor selection, Cload (x,y,z),
Cut-off frequency 1 Hz 10 Hz 20 Hz 50 Hz 100 Hz 200 Hz 500 Hz Capacitor value 5 F 0.5 F 250 nF 100 nF 50 nF 25 nF 10 nF
LIS344AL
4.1
Soldering information
The LGA package is compliant with the ECOPACK, RoHs and "Green" standard. It is qualified for soldering heat resistance according to JEDEC J-STD-020C. Leave "Pin 1 Indicator" unconnected during soldering. Land pattern and soldering recommendations are available at www.st.com/mems.
4.2
Output response vs. orientation
Figure 4. Output response vs. orientation
X=1.50V (0g) Y=1.80V (+1g) Z=1.50V (0g)
Bottom
X=1.80V (+1g) Y=1.50V (0g) Z=1.50V (0g) X=1.20V (-1g) Y=1.50V (0g) Z=1.50V (0g)
Top Top
X=1.50V (0g) Y=1.50V (0g) Z=1.20V (-1g)
X=1.50V (0g) Y=1.50V (0g) Bottom Z=1.80V (+1g)
X=1.50V (0g) Y=1.20V (-1g) Z=1.50V (0g)
Earth's Surface
Figure 4 shows output voltage values of LIS344AL when powered at 3.0 V.
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LIS344AL
Package Information
5
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 5. LGA 16: mechanical data & package dimensions
Dimensions Ref.
A1 A2 A3 d D1 E1 L2 M N1 N2 P1 P2 T1 T2 k 3.850 3.850 0.160 0.200 0.300 4.000 4.000 1.950 0.100 0.650 0.980 1.750 1.525 0.400 0.300 0.050
mm Min. Typ. Max.
1.500 1.600 1.330
inch Min. Typ. Max.
0.0524 0.0591 0.0630
Outline and mechanical data
0.240 0.0063 0.0079 0.0094 0.0118 4.150 0.1516 0.1575 0.1634 4.150 0.1516 0.1575 0.1634 0.0768 0.0039 0.0256 0.0386 0.0689 0.0600 0.0157 0.0118 0.0020
LGA16L (4x4x1.5mm) Land Grid Array Package
7974136D
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Revision history
LIS344AL
6
Revision history
Table 7.
Date 17-Dec-2007
Document revision history
Revision 1 Initial release. Changes
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LIS344AL
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