LIS244AL MEMS motion sensor: 2-axis - ±2g ultracompact linear accelerometer Features ■ Single voltage supply operation ■ ± 2g full-scale ■ Output voltage, offset and sensitivity are ratiometric to the supply voltage ■ Factory trimmed device sensitivity and offset ■ Embedded self test ■ ECOPACK lead-free compliant ■ High shock survivability (10000g) Description The LIS244AL is an ultra compact consumer lowpower two-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. LGA 16 (4x4x1.5mm) The LIS244AL 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 LIS244AL is available in Land Grid Array package (LGA) and it is guarantee to operate over an extended temperature range of -40°C to +85°C. The LIS244AL 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. Device summary Order codes Temp range, ° C Package Packing LIS244AL -40°C to +85°C LGA-16 Tray LIS244ALTR -40°C to +85°C LGA-16 Tape & Reel Note: June 2007 Tape & Reel parts are compliant to International Standard EIA-481. Rev 1 1/15 www.st.com 15 Contents LIS244AL Contents 1 2 3 4 Block diagram & pins description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Mechanical and electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1 Sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2 IC Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3 Factory calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.1 Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.2 Output Response vs. orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2/15 LIS244AL Block diagram & pins description 1 Block diagram & pins description 1.1 Block diagram Figure 1. Block diagram X+ a Routx CHARGE AMPLIFIER Y+ MUX DEMUX YX- SELF TEST Voutx S/H Routy Vouty S/H TRIMMING CIRCUIT REFERENCE CLOCK St 1.2 Pin Description Figure 2. Pin Connection NC res X Vdd NC 1 1 12 Y NC NC ST Vouty GND NC NC 8 4 GND GND GND NC (TOP VIEW) DIRECTION OF THE DETECTABLE ACCELERATIONS VoutX (BOTTOM VIEW) 3/15 Block diagram & pins description Table 2. 4/15 LIS244AL Pin description Pin # Pin name Function 1 NC Not to be connected 2 ST Self test (logic 0: normal mode; logic 1: self-test mode) 3 GND 0V supply 4 NC Not to be connected 5 GND 0V supply 6 GND 0V supply 7 GND 0V supply 8 NC Not to be connected 9 NC Not to be connected 10 Vouty Output voltage Y channel 11 NC Not to be connected 12 Voutx Output voltage X channel 13 NC Not to be connected 14 Vdd Power supply 15 Res Connect to Vdd 16 NC Not to be connected LIS244AL Mechanical and electrical specifications 2 Mechanical and electrical specifications 2.1 Mechanical characteristics (Temperature range -40°C to +85°C). All the parameters are specified @ Vdd =3.0V, T = 25°C unless otherwise noted Table 3. Symbol Mechanical characteristics(1) Parameter Ar Acceleration range(3) So Sensitivity(5) Test condition 0.140*Vdd 10% Sensitivity change vs temperature Delta from +25°C Voff Zero-g level(4) T = 25°C NL CrossAx Cross-axis An Vt 0.140*Vdd Vdd/2-15% Best fit straight line (6) Acceleration noise density Vdd=3.0V T = 25°C Vdd=3.0V Self test output voltage X axis change(7), T = 25°C Vdd=3.0V Y axis Fres Sensing element resonant frequency(8) Top Operating temperature range Wh Product weight X,Yaxis Vdd/2 Unit g 0.140*Vdd+ 10% 0.01 Zero-g level change vs Delta from +25°C temperature Non linearity(5) Max. ±2 SoDr OffDr Typ.(2) Min. V/g %/°C Vdd/2+15% V 1 mg/°C ±0.5 % FS ±2 % 220 µg/ Hz 105 mV 105 mV 4.0 kHz -40 +85 0.040 °C gram 1. The product is factory calibrated at 3.0V. The operational power supply range is from 2.4V to 3.6V. 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=4.0kHz. Sensor bandwidth=1/(2*π*32kΩ*Cload) 5/15 Mechanical and electrical specifications 2.2 LIS244AL Electrical characteristics (Temperature range -40°C to +85°C) All the parameters are specified @ Vdd =3.0V, T=25°C unless otherwise noted Table 4. Symbol Electrical characteristics(1) Parameter Vdd Supply voltage Idd Supply current Vst Self test input Rout Test condition Min. Typ.(2) Max. Unit 2.4 3.0 3.6 V 0.65 Logic 0 level 0 0.8 V Logic 1 level 2.0 Vdd V Output impedance of Voutx, Vouty 1. The product is factory calibrated at 3.0V 2. Typical specifications are not guaranteed Note: 6/15 mA Minimum resonance frequency Fres=4.0kHz. Device bandwidth=1/(2*π*32kΩ*Cload) 32 kΩ LIS244AL 2.3 Mechanical and electrical specifications 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 Vdd Supply voltage Vin Input voltage on any control pin (ST) Maximum value Unit -0.3 to 6 V -0.3 to Vdd +0.3 V 3000g for 0.5 ms APOW Acceleration (any axis, powered, Vdd=3.0V) AUNP Acceleration (any axis, not powered) TSTG Storage temperature range 10000g for 0.1 ms 3000g for 0.5 ms 10000g for 0.1 ms -40 to +125 °C 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 3.0V powered sensor Vdd/2 = 1500mV. A deviation from ideal 0-g level (1500mV 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. 7/15 Mechanical and electrical specifications LIS244AL 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, 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 2.5nF 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. 8/15 LIS244AL 3 Functionality Functionality The LIS244AL is an ultra compact low-power, analog output two-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 pF 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 two 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. 9/15 Application hints 4 LIS244AL Application hints Figure 3. LIS244AL Electrical connection Vdd GND GND 100nF 10µF 1 16 15 14 13 1 ST Optional 12 LIS244AL 2 11 (top view) 3 9 5 6 7 Vout x Cload x X Y Optional 10 4 Pin 1 indicator Vout y Cload y (TOP VIEW) DIRECTION OF THE DETECTABLE ACCELERATIONS 8 GND Digital signals Power supply decoupling capacitors (100nF ceramic or polyester + 10µF Aluminum) should be placed as near as possible to the device (common design practice). The LIS244AL allows to band limit Voutx, Vouty through the use of external capacitors. The recommended frequency range spans from DC up to 2.0kHz. In particular, capacitors are added at output Voutx, Vouty 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: Equation 1 1 f t = ---------------------------------------------------------------2π ⋅ R out ⋅ C load ( x, y ) Taking into account that the internal filtering resistor (Rout) has a nominal value equal to 32kΩ, the equation for the external filter cut-off frequency may be simplified as follows: Equation 2 5µF f t = -------------------------- [ Hz ] C load x, y 10/15 LIS244AL Application hints The tolerance of the internal resistor can vary typically of ±20% within its nominal value of 32kΩ; thus the cut-off frequency will vary accordingly. A minimum capacitance of 2.5nF for Cload(x, y) is required. Table 6. 4.1 Filter Capacitor Selection, Cload (x,y), 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 Soldering information The LGA package is compliant with the ECOPACK, RoHs and “Green” standard. Pin1 indicator is electrically connected to pin 1. Leave pin 1 indicator unconnected during soldering. 4.2 Output Response vs. orientation Figure 4. Output response vs. orientation X=1.50V (0g) Y=1.83V (+1g) Top X=1.50V (0g) Y=1.50V (0g) Bottom X=1.83V (+1g) Y=1.50V (0g) TOP VIEW X=1.17V (-1g) Y=1.50V (0g) Top X=1.50V (0g) Y=1.50V (0g) Bottom X=1.50V (0g) Y=1.17V (-1g) Earth’s Surface Figure 4 refers to LIS244AL powered at 3.0V. 11/15 Package information 5 LIS244AL 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. 12/15 LIS244AL Package information Figure 5. LGA 16: mechanical data & package dimensions Dimensions Ref. mm Min. A1 Typ. 1 A2 inch Max. Min. 1.60 Typ. Max. 0.039 0.063 1.33 Outline and mechanical data 0.052 A3 0.160 0.20 0.24 0.006 0.008 0.009 D1 3.850 4.0 4.150 0.152 0.157 0.163 E1 3.850 4.0 4.150 0.152 0.157 0.163 L 0.65 0.026 L1 1.95 0.077 N 0.98 0.039 N1 1.90 0.075 T1 0.40 0.016 T2 0.30 0.012 P1 1.750 0.069 P2 1.525 0.060 R 0.30 0.012 S 0.10 0.004 k 0.05 0.0019 LGA 16 (4x4x1.5mm) 7974136 13/15 Revision history 6 LIS244AL Revision history Table 7. 14/15 Document revision history Date Revision 29-Jun-2007 1 Changes Initial release LIS244AL 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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