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preliminary data this is preliminary information on a new product now in deve lopment or undergoing evaluation. details are subject to change without notice. march 2009 rev 1 1/14 14 LIS352AX mems inertial sensor 3-axis - 2g absolute anal og output accelerometer features absolute 0-g leve l and sensitivity very high stability over temperature 3 acceleration channels plus multiplexed analog output factory trimmed device sensitivity and 0-g level power-down mode embedded self test 10000g high shock survivability ecopack? rohs and ?green? compliant (see section 5 ) applications free-fall detection for data protection mobile and battery operated terminals gaming and virtual reality input devices antitheft systems and inertial navigation description the LIS352AX is the new small size, low-power three-axis linear accelerometer that includes a sensing element and an ic interface able to provide an absolute analog signal to the external world. 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. the LIS352AX has a full scale of 2g and it is capable of measuring accelerations over a maximum bandwidth of 2.0 khz. the device bandwidth may be reduced by using external capacitances. the self-test capability a llows the user to check the functioning of the system. an embedded multiplexer a llows to redirect the analog outputs onto a single pin for operation with a single channel a/d converter. st is already in the field with several hundreds million sensors with excellent acceptance from the market in terms of quality, reliability and performance. the LIS352AX is provided in plastic land grid array (lga) package. several years ago st pioneered successfully the usage of this package for accelerometers. today st has the widest manufa cturing capability and strongest expertise in the world for production of sensor in plastic lga package. lga14 (3x5x0.9mm) table 1. device summary order codes temperature range, cpackage packing LIS352AX -40c to +85c lga-14 tray LIS352AXtr -40c to +85c lga-14 tape and reel (16mm, pitch 0.8mm) www.st.com
contents LIS352AX 2/14 contents 1 block diagram and pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 mechanical and electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4 terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3 functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1 sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2 ic interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3 factory calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4 application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.1 soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.2 output response vs. orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
LIS352AX block diagram and pin description 3/14 1 block diagram and pin description 1.1 block diagram figure 1. block diagram 1.2 pin description figure 2. pin connection s/h s/h routx routz reference trimming circuit clock s/h routy charge amplifier demux voutx voutz vouty aux_in vout s1 s0 mux y+ z+ y- z- x+ x- a self test mux (top view) directions of detectable accelerations (bottom view) 1 6 res res s0 s1 st pd vouty voutz gnd vout aux_in vdd voutx res y 1 x z 13 8
block diagram and pin description LIS352AX 4/14 table 2. pin description pin # pin name function 1 reserved connect to gnd 2 reserved connect to vdd 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 0v supply 11 vout multiplexer output 12 aux_in auxiliary input 13 vdd power supply 14 reserved connect to vdd
LIS352AX mechanical and electrical specifications 5/14 2 mechanical and electrical specifications 2.1 mechanical characteristics @ t = 25 c unless otherwise noted table 3. mechanical characteristics (1) symbol parameter test condition min. typ. (2) max. unit ar acceleration range (3) 2.0 g so sensitivity (4) 0.363 - 5% 0.363 0.363 + 5% v/g sodr sensitivity change vs. temperature delta from +25c 0.01 %/c voff zero-g level (4) t = 25c 1.25 - 6% 1.25 1.25 + 6% v offdr zero-g level change vs temperature delta from +25c 0.3 mg/c nl non linearity (5) best fit straight line 0.5 % fs crossax cross-axis (6) 2 % an acceleration noise density vdd=3.3v 100 g/ vt self test output voltage change (7) t = 25c x axis +210 mv t = 25c y axis +210 mv t = 25c z axis +290 mv fres sensing element resonant frequency (8) x, y, z axis 2.0 khz top operating temperature range -40 +85 c wh product weight 30 mgram 1. product is factory calibrated at 3.3 v 2. typical specificat ions are not guaranteed 3. guaranteed by wafer level test and measurement of initial offset and sensitivity 4. zero-g level and sensitivity are not 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. minimum resonance frequency fres=2 .0 khz. sensor bandwidth=1/(2* *32 k ? *cload), with cload>2.5 nf hz
mechanical and electrical specifications LIS352AX 6/14 2.2 electrical characteristics @ t = 25c unless otherwise noted table 4. electrical characteristics (1) symbol parameter test condition min. typ. (2) max. unit vdd supply voltage 2.16 3.3 3.6 v 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 a vst self test input logic 0 level 0 0.2*vdd v logic 1 level 0.8*vdd vdd vs0 s0 input logic 0 level 0 0.2*vdd logic 1 level 0.8*vdd vdd vs1 s1 input logic 0 level 0 0.2*vdd logic 1 level 0.8*vdd vdd rout output impedance of voutx, vouty, voutz 32 k ? cload capacitive load drive for voutx, vouty, voutz (3) 2.5 nf rmux series resistance of multiplexer input vs. vout 1 k ? cloadmux capacitive load drive for multiplexed output vout 10 pf to n turn-on time at exit from power-down mode cload in f 160*cload+0.3 ms 1. product is factory calibrated at 3.3 v 2. typical specificat ions are not guaranteed 3. minimum resonance frequency fres=2 .0 khz. device bandwidth=1/(2* *32 k ? *cload), with cload>2.5 nf
LIS352AX mechanical and electrical specifications 7/14 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 a nd functional operation of the device under these conditions is not implied. ex posure to maximum rating conditions for extended periods may affect device reliability. table 5. absolute maximum ratings symbol ratings maximum value unit vdd supply voltage -0.3 to 6 v vin input voltage on any control pin (pd, st, s0, s1) -0.3 to vdd +0.3 v v aux_in aux_in input voltage -0.3 to vdd +0.3 v a pow acceleration (any axis, powered, vdd=3.3v) 3000g for 0.5 ms 10000g for 0.1 ms a unp acceleration (any axis, not powered) 3000g for 0.5 ms 10000g for 0.1 ms t stg storage temperature range -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
mechanical and electrical specifications LIS352AX 8/14 2.4 terminology sensitivity describes the gain of the sensor and can be determined by applying 1g acceleration to it. as the sensor can measur e 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 s ensitivity 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 me asure 0g in x axis and 0g in y axis whereas the z axis will measure 1g. a deviation from id eal 0-g level (1250mv 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 me chanical 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 lif etime. 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 al 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 pi n is tied at vdd an actuation force is applied to the sensor, simulating a definite input acce leration. in this case the sensor outputs will exhibit a voltage change in their 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 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 pa rticular application should be chosen to get the best results.
LIS352AX functionality 9/14 3 functionality the LIS352AX 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 s ilicon 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 capacit ive 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. 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, the sensitivity and the offset will not change. the feature allo ws the coupling of the sensor with an adc having a fixed voltage reference independent from vdd. 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.
application hints LIS352AX 10/14 4 application hints figure 3. LIS352AX electrical connection 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 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. capacitors must be added at output pins to implement low-pass filtering for antialiasing and noise reduction, even if the only multiplexed output ( vout ) is used. the equation for the cut-off frequency ( f t ) of the external filters is: equation 1 taking into account that the internal filtering resistor (r out ) has a nominal value equal to 32 k ? , the equation for the external filter cut-off frequency may be simplified as follows: equation 2 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 accordin gly. a minimum capacitance of 2.5 nf for c load (x, y, z) is required in any case. directions of detectable accelerations y 1 x z digital signals voutx LIS352AX vouty cload y cload x (top view) optional optional 1 st s1 s0 pd vout z optional cload z 6 8 13 aux_in 100nf 10f gnd gnd vdd vout gnd pin 1 indicator optional analog signals cloadmux gnd f t 1 2 r out c load xyz ,, () ?? ------------------------------------------------------------------------ - = f t 5 f c load xyz ,, () -------------------------------------- - hz [] =
LIS352AX application hints 11/14 an external capacitor can be added to the vout pin. values below 10 pf are recommended. 4.1 soldering information the lga package is compliant with the ecopack?, rohs and ?green? standard. it is qualified for soldering heat resist ance according to jedec j-std-020c. leave ?pin 1 indicator? unconnected during soldering. land pattern and soldering recommendations are available at www.st.com/ . 4.2 output response vs. orientation figure 4. output response vs. orientation table 6. filter capacitor selection, c load (x,y,z) cut-off frequency capacitor value 1 hz 5 f 10 hz 0.5 f 20 hz 250nf 50 hz 100nf 100 hz 50nf 200 hz 25nf 500 hz 10nf table 7. 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 earth?s surface x=1.25v (0g) y=1.25v (0g) z=1.61v (+1g) x=1.25v (0g) y=1.25v (0g) z=0.89v (-1g) top view x=0.89v (-1g) y=1.25v (0g) x=1.61v (+1g) y=1.25v (0g) x=1.25v (0g) y=0.89v (-1g) x=1.25v (0g) y=1.61v (+1g) z=1.25v (0g) z=1.25v (0g) z=1.25v (0g) z=1.25v (0g) to p bottom to p bottom
package information LIS352AX 12/14 5 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 outline and mechanical data dim. mm inch min. typ. max. min. typ. max. a1 0.920 1.000 0.0362 0.0394 a2 0.700 0.0275 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 1.200 0.0472 p1 0.965 0.975 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 l and g rid a rray package 7773587 c
LIS352AX revision history 13/14 6 revision history table 8. document revision history date revision changes 26-mar-2009 1 initial release
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