LIS302ALK MEMS motion sensor 3-axis - ±2g analog output "piccolo" accelerometer Preliminary Data Features ■ 3.0V to 3.6V supply voltage ■ ~2mW power consumption ■ ±2g full-scale ■ 3 axes acceleration channels ■ Ratiometric output voltage ■ Embedded self test ■ Power down mode ■ 10000g high shock survivability ■ ECOPACK® RoHS and “Green” compliant (see Section 5) LGA-14 (3x5x0.9mm) Description The LIS302ALK is a miniaturized low-power three-axis linear accelerometer. It includes a sensing element and an IC interface 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 motion sensors and actuators in silicon. The IC interface is manufactured using a CMOS process that allows to design a dedicated circuit which is trimmed to better match the sensing element characteristics. The device can be operated from 2.16V to 3.6V. The LIS302ALK has a full scale of ±2g and it 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 sensor in the final application without thew need to move or tilt the sensor. The LIS302ALK is available in plastic Thin Land Grid Array package (TLGA) and it is guaranteed to operate over an extended temperature range from -40°C to +85°C. The LIS302ALK 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. Order codes Part number Temperature range, °C Package Packing LIS302ALK -40°C to +85°C LGA-14 Tray LIS302ALKTR -40°C to +85°C LGA-14 Tape & reel Note: October 2006 Tape & reel parts are compliant to International Standard EIA-481. Rev 1 This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice. 1/14 www.st.com 14 Contents LIS302ALK Contents 1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 2 3 4 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2/14 LIS302ALK 1 Block diagram Block diagram Figure 1. Block diagram X+ CHARGE AMPLIFIER Y+ Z+ a MUX Routx Voutx Routy Vouty Routz Voutz S/H DEMUX S/H ZYX- S/H REFERENCE SELF TEST 1.1 TRIMMING CIRCUIT CLOCK Pin description Figure 2. Pin connection Z 1 Y 8 Voutx (TOP VIEW) DIRECTION OF THE DETECTABLE ACCELERATIONS Vdd res res GND Voutz Vouty 1 res res res res ST PD LIS302AL X res 13 6 (BOTTOM VIEW) 3/14 Block diagram LIS302ALK Table 1. 4/14 Pin description Pin # Pin Name Function 1 Reserved Connect to Vdd 2 Reserved Connect to Vdd 3 Reserved Connect to Gnd 4 Reserved Connect 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 0V supply 11 Reserved Leave unconnected 12 Reserved Connect to Gnd 13 Vdd 14 Reserved Power supply Connect to Vdd LIS302ALK Mechanical and electrical specifications 2 Mechanical and electrical specifications 2.1 Mechanical characteristics. Table 2. Mechanical characteristics(1) All parameters are specified @ Vdd =3.3V, T = 25°C unless otherwise noted Symbol Ar So Parameter Test Condition Min. Max. Unit ±2.0 Acceleration range(3) Sensitivity Typ.(2) (4) 0.415 0.440 g 0.465 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 ±0.5 mg/°C Non Linearity(5) Best fit straight line ±0.5 % FS ±2 % 200 µg/ Hz OffDr NL CrossAx An Vt ±0.01 Vdd/2-6% Cross-Axis(6) Acceleration Noise Density Self test output voltage change(7),(8) Fres Sensing Element Resonant Frequency(9) Top Operating Temperature Range Wh Product Weight Vdd=3.3V Vdd/2 %/°C Vdd/2+6% V T = 25°C Vdd=3.3V X axis +80 +220 mV T = 25°C Vdd=3.3V Y axis +80 +220 mV T = 25°C Vdd=3.3V Z axis +80 +220 mV all axes 2.0 kHz -40 +85 30 °C mgram 1. The product is factory calibrated at 3.3V. The operational power supply range is specified in table 3. Since the device is ratiometric 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 ratiometric to supply voltage 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. “Self test output voltage change” varies cubically with supply voltage 9. Minimum resonance frequency Fres=2.0kHz. Sensor bandwidth=1/(2*π*32kΩ*Cload) 5/14 Mechanical and electrical specifications LIS302ALK 2.2 Electrical characteristics Table 3. Electrical characteristics(1) All parameters are specified @ Vdd =3.3V, T=25°C unless otherwise noted Symbol Parameter Test Condition Vdd Supply Voltage Idd Supply Current mean value PD pin connected to GND Supply Current in Power Down Mode PD pin connected to Vdd IddPdn Vst Typ.(2) Min. Unit V 0.65 mA 1 µA Logic 0 level at Vdd=3.3V 0 0.8 V Logic 1 level at Vdd=3.3V 2.0 Vdd V Self Test Input Rout Output impedance of Voutx, Vouty, Voutz Cload Capacitive Load Drive for Voutx, Vouty, Voutz(3) Ton Turn-On Time at exit from Power Down mode Top Operating Temperature Range 32 kΩ 2.5 Cload in μF nF 160*Cload+0.3 -40 1. The product is factory calibrated at 3.3V. 2. Typical specifications are not guaranteed 3. Minimum resonance frequency Fres=2.0kHz. Device bandwidth=1/(2*π*32kΩ*Cload) 6/14 Max. ms +85 °C LIS302ALK 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 4. Absolute maximum ratings Symbol Ratings Vdd Supply voltage Vin Input Voltage on Any Control pin (PD, 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=3.3V) AUNP Acceleration (Any axis, Not powered) TSTG Storage Temperature Range 10000g for 0.1 ms 3000g for 0.5 ms ESD 10000g for 0.1 ms Electrostatic Discharge Protection -40 to +150 °C 2 (HBM) KV 1.5 (CDM) KV 200 (MM) 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 whereas the Z axis will measure +1g. 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 7/14 Mechanical and electrical specifications LIS302ALK over lifetime. The Zero-g level tolerance describes the range of Zero-g levels of a population of sensors. Self Test allows to check the sensor functionality without moving it. 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 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. 8/14 LIS302ALK 3 Functionality Functionality The LIS302ALK is an “piccolo” 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 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. 9/14 Application hints 4 LIS302ALK Application hints Figure 3. LIS302ALK electrical Connection LIS302ALK (top view) Vdd Vdd GND 1 13 LIS302AL GND ST 100nF Z GND 10μF X Pin 1 indicator GND Y GND Optional Vout z Cload z PD 6 1 DIRECTION OF THE DETECTABLE ACCELERATIONS 8 Optional Vout Y Cload y Optional Digital signals Cload x Vout X Power supply decoupling capacitors (100nF ceramic or polyester + 10µF Aluminum) should be placed as near as possible to the device (common design practice). The LIS302ALK allows to band limit Voutx, Vouty and Voutz through the use of external capacitors. The recommended frequency range spans from DC up to 2.0kHz. 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 = ---------------------------------------------------------------2π ⋅ R out ⋅ C load ( x, y, z ) 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: 5μF f t = ----------------------------------- [ Hz ] C load ( x, y, z ) 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, z) is required in any case. 10/14 LIS302ALK Application hints Table 5. 4.1 Filter capacitor selection, Cload (x,y,z) 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.It is qualified for soldering heat resistance according to JEDEC J-STD-020C. Pin1 indicator is electrically connected to pin 1. 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=1.17V (-1g) Y=1.65V (0g) Z=1.65V (0g) Bottom X=1.65V (0g) Y=2.13V (+1g) Z=1.65V (0g) TOP VIEW X=2.13V (+1g) Y=1.65V (0g) Z=1.65V (0g) Note: X=1.65V (0g) Y=1.17V (-1g) Z=1.65V (0g) Top Top X=1.65V (0g) Y=1.65V (0g) Z=1.17V (-1g) X=1.65V (0g) Y=1.65V (0g) Bottom Z=2.13V (+1g) Earth’s Surface Figure 4 refers to LIS302ALK powered at 3.3V. 11/14 Package information 5 LIS302ALK 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 14: Mechanical Data & Package Dimensions mm inch DIM. MIN. A1 TYP. MAX. 0.920 1.000 0.0362 0.0394 0.700 0.0275 A2 MIN. TYP. MAX. A3 0.180 0.220 0.260 0.0071 0.0087 0.0102 D1 2.850 3.000 3.150 0.1122 0.1181 0.1240 E1 4.850 5.000 5.150 0.1909 0.1968 0.2027 e 0.800 0.0315 d 0.300 0.0118 L1 4.000 0.1575 N 1.360 0.0535 N1 P1 1.200 0.965 0.975 OUTLINE AND MECHANICAL DATA 0.0472 0.985 0.0380 0.0384 0.0386 P2 0.640 0.650 0.660 0.0252 0.0256 0.0260 T1 0.750 0.800 0.850 0.0295 0.0315 0.0335 T2 0.450 0.500 0.550 0.0177 0.0197 0.0217 R 1.200 1.600 0.0472 0.0630 h 0.150 0.0059 k 0.050 0.0020 i 0.100 0.0039 s 0.100 0.0039 LGA14 (3x5x0.92mm) Pitch 0.8mm Land Grid Array Package 7773587 C 12/14 LIS302ALK 6 Revision history Revision history Table 6. Document revision history Date Revision 30-Oct-2006 1 Changes Initial release. 13/14 LIS302ALK Please Read Carefully: Information in this document is provided solely in connection with ST products. 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