LIS352AX
MEMS inertial sensor: 3-axis 2 g absolute analog-output "piccolo" accelerometer
Features
Absolute 0-g level and sensitivity Excellent stability over temperature 3 acceleration channels plus multiplexed analog output Factory-trimmed device sensitivity and 0-g level Power-down mode Embedded self-test 10000 g high shock survivability ECOPACK RoHS and "Green" compliant (see Section 6) The LIS352AX has a full-scale of 2 g and is capable of measuring accelerations over a maximum bandwidth of 2.0 kHz. The device bandwidth may be reduced by using external capacitors. The self-test capability allows the user to check the functioning of the system. An embedded multiplexer allows the redirection of the analog outputs onto a single pin for operation with a single-channel A/D converter. ST is already in the field with several hundred million sensors which have received excellent acceptance from the market in terms of quality, reliability and performance. The LIS352AX is provided in a plastic land grid array (LGA) package. Several years ago ST successfully pioneered the use of this package for accelerometers. Today, ST has the widest manufacturing capability and strongest expertise in the world for production of sensors in plastic LGA packages.
LGA-14 (3x5x0.9mm)
Applications
Free-fall detection for data protection Tilting applications Mobile and battery-operated terminals Gaming and virtual reality input devices Anti-theft systems and Inertial navigation
Description
The LIS352AX is a new small size, low-power 3axis linear accelerometer that includes a sensing element and an IC interface capable of providing an absolute analog signal to the external world. The IC interface is manufactured using a CMOS process that allows a high level of integration to design a dedicated circuit trimmed to better match the sensing element characteristics.
Table 1.
Device summary
Temperature range, C -40C to +85C -40C to +85C Package LGA-14 LGA-14 Packing Tray Tape and reel
Order code LIS352AX LIS352AXTR
February 2010
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Contents
LIS352AX
Contents
1 Block diagram and pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Pin connections and description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Mechanical and electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 2.2 Mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1 3.2 3.3 3.4 3.5 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Zero-g level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Self-test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Output impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4
Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1 4.2 4.3 Sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 IC interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Factor y calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5
Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 5.2 Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Output response vs. orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6 7
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
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Block diagram and pin description
1
Block diagram and pin description
Figure 1. Block diagram
Routx
X+ Y+ Z+
CHARGE AMPLIFIER
Voutx
S/H
a
ZYX-
Routy MUX DEMUX S/H
Vouty
Routz S/H
Voutz Vout MUX
SELF-TEST
REFERENCE
TRIMMING CIRCUIT
CLOCK
Aux_in S1 S0
AM06049v1
1.1
Pin connections and description
Figure 2. Pin connection
Z X 1
Vdd Aux_in Vout GND
Reserved
13
1
NC Reserved S0 S1 ST
Y
Voutz Vouty
(TOP VIEW) DIRECTIONS OF DETECTABLE ACCELERATIONS (BOTTOM VIEW) 8 6
PD
Voutx
AM06050v1
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Block diagram and pin description Table 2.
Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14
LIS352AX
Pin description
Pin Name NC Reserved S0 S1 ST PD Voutx Vouty Voutz GND Vout Aux_in Vdd Reserved Internally not connected Connect to Vdd Mux selector 0 (connect to Vdd or to GND) Mux selector 1 (connect to Vdd or to GND) Self-test (logic 0: normal mode; logic 1: self-test) Power-down (logic 0: normal mode; logic 1: power-down mode) Output voltage X channel Output voltage Y channel Output voltage Z channel 0 V supply Multiplexer output Auxiliar y input Power supply Connect to Vdd Function
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Mechanical and electrical specifications
2
2.1
Mechanical and electrical specifications
Mechanical characteristics
@ Vdd=3.3 V, T=25 C unless otherwise noted(a)
Table 3.
Symbol Ar So SoDr Voff OffDr NL
Mechanical characteristics
Parameter Acceleration range Sensitivity
(3) (2)
Test condition
Min.
Typ.(1) 2.0
Max.
Unit g
0.363 - 5% Delta from +25 C T = 25C Delta from +25 C Best fit straight line 1.25- 3.5%
0.363 0.01 1.25 0.3 0.5 2
0.363 + 5%
V/g %/C
Sensitivity change vs. temperature Zero-g level(4) Zero-g level change vs temperature Non linearity(4)
(5)
1.25+ 3.5%
V mg/C % FS % g/ H z
CrossAx Cross-axis An
Acceleration noise density
Vdd=3.3 V T = 25 C X axis 40 40 40 2.0 -40
100 550 550 550
mV mV mV kHz
Vt
Self-test output voltage change(6)
T = 25 C Y axis T = 25 C Z axis
Fres Top Wh
Sensing element resonant frequency(7) Operating temperature range Product weight
X, Y, Z axis
+85 30
C mgram
1. Typical specifications are not guaranteed 2. Guaranteed by wafer level test and measurement of initial offset and sensitivity 3. Zero-g level and sensitivity are absolute to supply voltage 4. Guaranteed by design 5. Contribution to the measuring output of an inclination/acceleration along any perpendicular axis 6. Self-test output voltage change" is defined as Vout(Vst=Logic1)-Vout(Vst=Logic0) 7. Minimum resonance frequency FRES=2.0 kHz. Sensor bandwidth=1/(2**32k*CLOAD), with CLOAD>2.5nF
a. The product is factory calibrated at 3.3 V. The operational power supply range is specified in Table 4.
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Mechanical and electrical specifications
LIS352AX
2.2
Electrical characteristics
@ Vdd=3.3 V, T=25 C unless otherwise noted(b)
Table 4.
Symbol Vdd Idd IddPdn Vst Vpd Vs0
Electrical characteristics
Parameter Supply voltage Supply current Supply current in power-down mode Self-test input Power-down input S0 Input Logic 1 level Logic 0 level 0.8*Vdd 0 0.8*Vdd 32 Vdd 0.2*Vdd Vdd k Mean value PD pin connected to GND PD pin connected to Vdd Logic 0 level Logic 1 level Logic 0 level 0 0.8*Vdd 0 Test condition Min. 2.16 Typ.(1) 3.3 0.3 1 0.2*Vdd Vdd 0.2*Vdd Max. 3.6 Unit V mA A V
Vs1
S1 input Logic 1 level Output impedance of Voutx, Vouty, Voutz Capacitive load drive for Voutx, Vouty, Voutz(2) Series resistance of multiplexer input vs. Vout Capacitive load drive for multiplexed output Vout Turn-on time at exit from power-down mode CLOAD in F 2.5
Rout
Cload
nF
Rmux
1
k
Cloadmux
10
pF
Ton
160*CLOAD+0.3
ms
1. Typical specifications are not guaranteed 2. Minimum resonance frequency FRES=2.0 kHz. Device bandwidth=1/(2**32k*CLOAD), with CLOAD>2.5nF
b. The product is factory calibrated at 3.3 V. The operational power supply range is specified in Table 3.
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Absolute maximum ratings
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 VAux_in APOW Supply voltage Input voltage on any control pin (PD, ST, S0, S1) Aux_in input voltage Acceleration (any axis, powered, Vdd=3.3V)
Absolute maximum ratings
Ratings Maximum Value -0.3 to 6 -0.3 to Vdd +0.3 -0.3 to Vdd +0.3 3000 g for 0.5 ms 10000 g for 0.1 ms 3000 g for 0.5 ms Unit V V V
AUNP TSTG
Acceleration (any axis, not powered) Storage temperature range
10000 g for 0.1 ms -40 to +125 4 (HBM) C kV kV V
ESD
Electrostatic discharge protection
1.5 (CDM) 200 (MM)
Note:
Supply voltage on any pin should never exceed 6.0 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
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Absolute maximum ratings
L IS352AX
3.1 3.2
Terminology Sensitivity
Sensitivity describes the gain of the sensor and can be determined by applying 1 g acceleration to it. Because the sensor can measure DC accelerations, this can be done easily by pointing the selected axis towards the ground, noting the output value, rotating the sensor 180 degrees (pointing towards the sky) and noting the output value again. By doing so, a 1 g acceleration is applied to the sensor. Subtracting the larger output value from the smaller one, and dividing the result by 2, produces the actual sensitivity of the sensor. This value changes very little over temperature (see sensitivity change vs. temperature) and over time. The sensitivity tolerance describes the range of sensitivities of a large number of sensors.
3.3
Zero-g level
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 0 g on both the X and Y axes, whereas the Z axis will measure 1 g. A deviation from the ideal 0-g level (1250 mV, in this case) is called Zero-g offset. Offset is to some extent a result of stress to the MEMS 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" in Table 3: Mechanical characteristics). The Zero-g level of an individual sensor is also very stable over its lifetime. The Zero-g level tolerance describes the range of Zero-g levels of a group of sensors.
3.4
Self-test
Self-test (ST) provides a means of testing of the mechanical and electrical parts of the sensor, allowing the seismic mass to be moved by through 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 exhibits a voltage change in its DC levels. 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 in Table 3, then the sensor is working properly and the parameters of the interface chip are within the defined specifications.
3.5
Output impedance
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 resonant frequency of the sensor. In general, the smallest possible bandwidth for a particular application should be chosen to obtain the best results.
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Functionality
4
Functionality
The LIS352AX is a 3-axis ultracompact low-power, analog output linear accelerometer packaged in a LGA package. The complete device includes a sensing element and an IC interface capable of taking information from the sensing element providing an analog signal to the external world.
4.1
Sensing element
A proprietary process is used to create a surface micro-machined accelerometer. The technology allows the creation of suspended silicon structures which are attached to the substrate at several points called "anchors" and are free to move in the direction of the sensed acceleration. To be compatible with traditional packaging techniques, a cap is placed on top of the sensing element to prevent blocking of the moving parts during the moulding phase of plastic encapsulation. When an acceleration is applied to the sensor, the proof mass shifts 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 a few pF, and when an acceleration is applied the maximum variation of the capacitive load is in the fF range.
4.2
IC interface
The complete signal processing utilizes a fully differential structure, while the final stage converts the differential signal into a single-ended signal to be compatible with external applications. 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 signal produced is then sent to three different S&Hs, one for each channel, and made available to the outside. The device provides an embedded multiplexer to allow the redirection of either the analog output signals Voutx, Vouty, and Voutz, or of an auxiliary input signal onto a single pin for operation with a single-channel A/D converter. All the analog parameters (output offset voltage and sensitivity) are absolute with respect to the voltage supply. Increasing or decreasing the voltage supply will not cause a change in the sensitivity and the offset. The feature allows the coupling of the sensor with an ADC, having a fixed voltage reference independent from Vdd.
4.3
Factory calibration
The IC interface is factory calibrated for sensitivity (So) and zero-g level (Voff). The trimming values are stored inside the device in 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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Application hints
LIS352AX
5
Application hints
Figure 3. LIS352AX electrical connection
f
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 LIS352AX allows band limiting of Voutx, Vouty and Voutz through the use of external capacitors. The recommended frequency range spans from DC up to 2.0 kHz. Capacitors must be added at the output pins to implement low-pass filtering for anti-aliasing and noise reduction, even if only the multiplexed output (Vout) is used. The equation for the cut-off frequency ( ft ) of the external filters is:
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 of 32 k, the equation for the external filter cut-off frequency may be simplified as follows:
1
5 F f t = -------------------------------------- [ H z ] C l o a d ( x, y, z )
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Application hints The tolerance of the internal resistor can vary 20% (typ) from 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. An external capacitor can be added to the Vout pin. Values below 10 pF are recommended. 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 0.5F 250nF 100nF 50nF 25nF 10nF
Table 7.
MUX I/O table
S1 pin 0 0 1 1 S0 pin 0 1 0 1 MUX status Vout=Voutx Vout=Vouty Vout=Voutz Vout=Aux_in
5.1
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.
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Application hints
LIS352AX
5.2
Output response vs. orientation
Figure 4. Output response vs. orientation
X=0.89V (-1g) Y=1.25V (0g) Z=1.25V (0g)
Bottom
X=1.25V (0g) Y=1.61V (+1g) Z=1.25V (0g) TOP VIEW X=1.25V (0g) Y=0.89V (-1g) Z=1.25V (0g)
Top Top
X=1.25V (0g) Y=1.25V (0g) Z=0.89V (-1g)
X=1.25V (0g) Y=1.25V (0g) Bottom Z=1.61V (+1g)
X=1.61V (+1g) Y=1.25V (0g) Z=1.25V (0g)
Earth' surface
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Package information
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Package information
In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK packages, depending on their level of environmental compliance. ECOPACK specifications, grade definitions and product status are available at: www.st.com. ECOPACK is an ST trademark. Figure 5. LGA-14: mechanical data and package dimensions
Dimensions mm Ref. Min. Typ. Max. Min. A1 A2 A3 D1 E1 N1 L1 P1 P2 T1 T2 d M k 0.16 2.85 4. 8 5 0.2 3 5 0.8 4 1.34 1.2 0.8 0.5 0.15 0.1 0.05 0.90 1 0.7 Typ. Max. 0.033 0.035 0.037 0.027 inch
O utl i ne and m e ch an ic al data
0.24 0.006 0.007 0.009 3.15 0.116 0.118 0.120 5.15 0.194 0.196 0.198 0.031 0.157 0.052 0.047 0.048 0.031 0.019 0.005 0.003 0.002
LGA-14 (3x5x0.9mm) pitch 0.8mm Land Grid Array Package
7773587E
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Revision history
LIS352AX
7
Revision history
Table 8.
Date 26-Mar-2009 02-Feb-2009
Document revision history
Revision 1 2 Initial datasheet Updated Section 2.1: Mechanical characteristics and Section 2.2: Electrical characteristics. Minor text changes Changes
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