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) LGA-14 (3x5x0.9mm) The self-test capability allows the user to check the functioning of the system. 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 An embedded multiplexer allows the redirection of the analog outputs onto a single pin for operation with a single-channel A/D converter. 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. 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. 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. Device summary Order code Temperature range, ° C Package Packing LIS352AX -40°C to +85°C LGA-14 Tray LIS352AXTR -40°C to +85°C LGA-14 Tape and reel February 2010 Doc ID 15530 Rev 2 1/15 www.st.com 15 Contents LIS352AX Contents 1 Block diagram and pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 2 3 4 5 Pin connections and description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Mechanical and electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.3 Zero-g level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.4 Self-test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.5 Output impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.1 Sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.2 IC interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.3 Factory calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.1 Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.2 Output response vs. orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2/15 Doc ID 15530 Rev 2 LIS352AX 1 Block diagram and pin description Block diagram and pin description Figure 1. Block diagram X+ CHARGE AMPLIFIER Y+ Z+ a MUX Routx Voutx Routy Vouty Routz Voutz S/H DEMUX S/H ZYXS/H Vout MUX SELF-TEST REFERENCE TRIMMING CIRCUIT CLOCK Aux_in S1 S0 AM06049v1 Pin connections and description Figure 2. Pin connection Reserved 1.1 Z 1 X Vdd 1 13 Aux_in Y Reserved Vout S0 GND S1 Voutz ST Vouty 6 8 PD Voutx (TOP VIEW) NC DIRECTIONS OF DETECTABLE ACCELERATIONS (BOTTOM VIEW) AM06050v1 Doc ID 15530 Rev 2 3/15 Block diagram and pin description Table 2. 4/15 LIS352AX Pin description Pin # Pin Name Function 1 NC 2 Reserved 3 S0 Mux selector 0 (connect to Vdd or to GND) 4 S1 Mux selector 1 (connect to Vdd or to GND) 5 ST Self-test (logic 0: normal mode; logic 1: self-test) 6 PD Power-down (logic 0: normal mode; logic 1: power-down mode) 7 Voutx Output voltage X channel 8 Vouty Output voltage Y channel 9 Voutz Output voltage Z channel 10 GND 0 V supply 11 Vout Multiplexer output 12 Aux_in Auxiliary input 13 Vdd Power supply 14 Reserved Internally not connected Connect to Vdd Connect to Vdd Doc ID 15530 Rev 2 LIS352AX Mechanical and electrical specifications 2 Mechanical and electrical specifications 2.1 Mechanical characteristics @ Vdd=3.3 V, T=25 °C unless otherwise noted(a) Table 3. Symbol Ar So Mechanical characteristics Parameter Acceleration range Sensitivity Test condition Min. (2) Typ.(1) Max. ±2.0 (3) 0.363 - 5% 0.363 Unit g 0.363 + 5% V/g SoDr Sensitivity change vs. temperature Delta from +25 °C Voff Zero-g level(4) T = 25°C Zero-g level change vs temperature Delta from +25 °C ±0.3 mg/°C Non linearity(4) Best fit straight line ±0.5 % FS ±2 % 100 µg/ Hz OffDr NL CrossAx Cross-axis An Vt ±0.01 1.25- 3.5% (5) Acceleration noise density Self-test output voltage change(6) Fres Sensing element resonant frequency(7) Top Operating temperature range Wh Product weight Vdd=3.3 V 1.25 %/°C 1.25+ 3.5% V T = 25 °C X axis 40 550 mV T = 25 °C Y axis 40 550 mV T = 25 °C Z axis 40 550 mV X, Y, Z axis 2.0 kHz -40 +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*π*32kΩ*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. Doc ID 15530 Rev 2 5/15 Mechanical and electrical specifications 2.2 LIS352AX Electrical characteristics @ Vdd=3.3 V, T=25 °C unless otherwise noted(b) Table 4. Symbol Electrical characteristics Parameter Test condition Min. Typ.(1) Max. Unit 2.16 3.3 3.6 V Vdd Supply voltage Idd Supply current Mean value PD pin connected to GND 0.3 mA IddPdn Supply current in power-down mode PD pin connected to Vdd 1 µA Vst Vpd Self-test input Power-down input Vs0 S0 Input Vs1 Logic 0 level 0 0.2*Vdd Logic 1 level 0.8*Vdd Vdd Logic 0 level 0 0.2*Vdd Logic 1 level 0.8*Vdd Vdd Logic 0 level 0 0.2*Vdd Logic 1 level 0.8*Vdd Vdd S1 input Rout Output impedance of Voutx, Vouty, Voutz Cload Capacitive load drive for Voutx, Vouty, Voutz(2) Rmux Series resistance of multiplexer input vs. Vout 1 kΩ Capacitive load drive for multiplexed output Vout 10 pF 160*CLOAD+0.3 ms Cloadmux Ton Turn-on time at exit from power-down mode 32 2.5 CLOAD in µF 2. Minimum resonance frequency FRES=2.0 kHz. Device bandwidth=1/(2*π*32kΩ*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. Doc ID 15530 Rev 2 kΩ nF 1. Typical specifications are not guaranteed 6/15 V LIS352AX 3 Absolute maximum ratings 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. Absolute maximum ratings Symbol Ratings Maximum Value Unit -0.3 to 6 V Vdd Supply voltage Vin Input voltage on any control pin (PD, ST, S0, S1) -0.3 to Vdd +0.3 V VAux_in Aux_in input voltage -0.3 to Vdd +0.3 V APOW Acceleration (any axis, powered, Vdd=3.3V) AUNP Acceleration (any axis, not powered) TSTG Storage temperature range 3000 g for 0.5 ms 10000 g for 0.1 ms 3000 g for 0.5 ms ESD Note: Electrostatic discharge protection 10000 g for 0.1 ms -40 to +125 °C 4 (HBM) kV 1.5 (CDM) kV 200 (MM) V 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 Doc ID 15530 Rev 2 7/15 Absolute maximum ratings 3.1 Terminology 3.2 Sensitivity LIS352AX 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. 8/15 Doc ID 15530 Rev 2 LIS352AX 4 Functionality 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. Doc ID 15530 Rev 2 9/15 Application hints 5 LIS352AX Application hints Figure 3. 6DD LIS352AX electrical connection ,)3!8 TOPVIEW 6DD '.$ N& : '.$ & 8 0ININDICATOR !UX)N /PTIONAL 3 6OUT #LOADMUX 3 9 '.$ /PTIONAL 34 6OUT: #LOADZ 0$ $)2%#4)/.3/& $%4%#4!", % !##%,%2!4)/. 3 /PTIONAL 6OUT9 #LOADY /PTIONAL !NALOGSIGNALS #LOADX 6OUT8 $IGITALSIGNALS !-V Power supply decoupling capacitors (100 nF ceramic or polyester + 10 µF 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: 1 f t = -----------------------------------------------------------------------2π ⋅ R out ⋅ C load ( x, y, z ) Taking into account that the internal filtering resistor (Rout) has a nominal value of 32 kΩ, the equation for the external filter cut-off frequency may be simplified as follows: 5µF f t = --------------------------------------- [ Hz ] C load ( x, y, z ) 10/15 Doc ID 15530 Rev 2 LIS352AX Application hints The tolerance of the internal resistor can vary ±20% (typ) from its nominal value of 32 kΩ; 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) Table 7. 5.1 Cut-off frequency Capacitor value 1 Hz 5 µF 10 Hz 0.5µF 20 Hz 250nF 50 Hz 100nF 100 Hz 50nF 200 Hz 25nF 500 Hz 10nF MUX I/O table S1 pin S0 pin MUX status 0 0 Vout=Voutx 0 1 Vout=Vouty 1 0 Vout=Voutz 1 1 Vout=Aux_in 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. Doc ID 15530 Rev 2 11/15 Application hints 5.2 LIS352AX 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=1.61V (+1g) Y=1.25V (0g) Z=1.25V (0g) 12/15 Doc ID 15530 Rev 2 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) Earth’ surface LIS352AX 6 Package information 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 Outline and inch mechanic al data Ref. Min. Typ. Max. Min. A1 0.90 A2 1 Typ. Max. 0.033 0.035 0.037 0.7 0.027 A3 0.16 0.2 0.24 0.006 0.007 0.009 D1 2.85 3 3.15 0.116 0.118 0.120 E1 4.85 5 5.15 0.194 0.196 0.198 N1 0.8 0.031 L1 4 0.157 P1 1.34 0.052 P2 1.2 0.047 0.048 T1 0.8 0.031 T2 0.5 0.019 d 0.15 0.005 M 0.1 0.003 k 0.05 0.002 LGA-14 (3x5x0.9mm) pitch 0.8mm Land Grid Array Package 7773587E Doc ID 15530 Rev 2 13/15 Revision history 7 LIS352AX Revision history Table 8. 14/15 Document revision history Date Revision Changes 26-Mar-2009 1 Initial datasheet 02-Feb-2009 2 Updated Section 2.1: Mechanical characteristics and Section 2.2: Electrical characteristics. Minor text changes Doc ID 15530 Rev 2 LIS352AX Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. 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