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june 2007 rev 1 1/15 15 lis244al mems motion sensor: 2-axis - 2g ultracompact linear accelerometer features single voltage supply operation 2 g full-scale output voltage, offset and sensitivity are ratiometric to the supply voltage factory trimmed device sensitivity and offset embedded self test ecopack lead-f ree compliant high shock survivability (10000g) description the lis244al is an ultra compact consumer low- power 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. 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 -40c to +85c. 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. note: tape & reel parts are compliant to international standard eia-481. lga 16 (4x4x1.5mm) table 1. device summary order codes temp range, cpackage packing lis244al -40c to +85c lga-16 tray LIS244ALTR -40c to +85c lga-16 tape & reel www.st.com
contents lis244al 2/15 contents 1 block diagram & pins 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
lis244al block diagram & pins description 3/15 1 block diagram & pins description 1.1 block diagram figure 1. block diagram 1.2 pin description figure 2. pin connection s/h s/h routx routy reference trimming circuit clock charge amplifier mux demux voutx vouty y+ y- x+ x- a self test st (top view) direction of the detectable accelerations (bottom view) y 1 x nc st gnd nc voutx nc vouty nc gnd gnd gnd nc vdd res nc nc 1 4 8 12
block diagram & pins description lis244al 4/15 table 2. 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 5/15 2 mechanical and electrical specifications 2.1 mechanical characteristics (temperature range -40c to +85c). all the parameters are specified @ vdd =3.0v, t = 25c unless otherwise noted table 3. mechanical characteristics (1) symbol parameter test condition min. typ. (2) max. unit ar acceleration range (3) 2g so sensitivity (5) 0.140*vdd - 10% 0.140*vdd 0.140*vdd+ 10% v/g sodr sensitivity change vs temperature delta from +25c 0.01 %/c voff zero-g level (4) t = 25c vdd/2-15% vdd/2 vdd/2+15% v offdr zero-g level change vs temperature delta from +25c 1 mg/c nl non linearity (5) best fit straight line 0.5 % fs crossax cross-axis (6) 2% an acceleration noise density vdd=3.0v 220 g/ vt self test output voltage change (7), t = 25c vdd=3.0v x axis 105 mv t = 25c vdd=3.0v y axis 105 mv fres sensing element resonant frequency (8) x,yaxis 4.0 khz to p operating temperature range -40 +85 c wh product weight 0.040 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 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 essentially rati ometric 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* *32k ? *cload) hz
mechanical and electrical specifications lis244al 6/15 2.2 electrical characteristics (temperature range -40c to +85c) all the parameters are specified @ vdd =3.0v, t=25c unless otherwise noted table 4. electrical characteristics (1) 1. the product is factory calibrated at 3.0v symbol parameter test condition min. typ. (2) 2. typical specificat ions are not guaranteed note: minimum resonance fre quency fres=4.0khz. device bandwidth=1/(2* *32k ? *cload) max. unit vdd supply voltage 2.4 3.0 3.6 v idd supply current 0.65 ma vst self test input logic 0 level 0 0.8 v logic 1 level 2.0 vdd v rout output impedance of voutx, vouty 32 k ?
lis244al mechanical and electrical specifications 7/15 2.3 absolute maximum ratings stresses above those listed as ?absolute ma ximum 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. 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 se nsitivity 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 prec ise 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 boar d 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 ve ry stable over lifetime. the zero-g level tolerance describes the range of zero-g levels of a population of sensors. 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 (st) -0.3 to vdd +0.3 v a pow acceleration (any axis, powered, vdd=3.0v) 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 lis244al 8/15 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 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 which is depending on the supply voltage through the device sensitivity. when st is activated, th e 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 signal s change within the amplitude specified inside ta bl e 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 ex ternal 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 pa rticular application should be chosen to get the best results.
lis244al functionality 9/15 3 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 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 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 de creasing the voltage supply, t he 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.
application hints lis244al 10/15 4 application hints figure 3. lis244al electrical connection power supply decoupling capacitors (100nf ceramic or polyester + 10 f 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 (f t ) of the external filters is in this case: equation 1 taking into account that the internal filtering resistor (r out ) has a nominal value equal to 32k ? , the equation for the external filter cut-off frequency may be simplified as follows: equation 2 digital signals lis244al (top view) (top view) direction of the detectable accelerations y 1 x st gnd 1 4 9 12 vdd gnd gnd 100nf 10 f vout y optional cload y vout x cload x optional 5 16 2 3 67 8 10 11 15 14 13 pin 1 indicator f t 1 2 r out c load xy , () ?? ---------------------------------------------------------------- = f t 5 f c load xy , ------------------------- - hz [] =
lis244al application hints 11/15 the tolerance of the internal resistor can vary typically of 20% within its nominal value of 32k ? ; thus the cut-off frequency will vary accord ingly. a minimum capacitance of 2.5nf for c load (x, y) is required. 4.1 soldering information the lga package is compliant with the ecopack, rohs and ?green? standard. pin1 indicator is electrically connected to pi n 1. leave pin 1 indicator unconnected during soldering. 4.2 output response vs. orientation figure 4. output response vs. orientation figure 4 refers to lis244al powered at 3.0v. table 6. filter capacitor selection, c load (x,y), 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 earth?s surface x=1.50v (0g) y=1.50v (0g) top view x=1.50v (0g) y=1.83v (+1g) x=1.50v (0g) y=1.17v (-1g) x=1.17v (-1g) y=1.50v (0g) x=1.83v (+1g) y=1.50v (0g) to p bottom x=1.50v (0g) y=1.50v (0g) to p bottom
package information lis244al 12/15 5 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.
lis244al package information 13/15 figure 5. lga 16: mechanical data & package dimensions dimensions ref. mm inch min. typ. max. min. typ. max. a1 1 1.60 0.0 39 0.06 3 a2 1. 33 0.052 a 3 0.160 0.20 0.24 0.006 0.00 8 0.00 9 d1 3 . 8 50 4.0 4.150 0.152 0.157 0.16 3 e1 3 . 8 50 4.0 4.150 0.152 0.157 0.16 3 l 0.65 0.026 l1 1. 9 5 0.077 n0. 98 0.0 39 n1 1. 9 0 0.075 t1 0.40 0.016 t2 0. 3 0 0.012 p1 1.750 0.06 9 p2 1.525 0.060 r0. 3 0 0.012 s 0.10 0.004 k0.05 0.001 9 lga 16 (4x4x1.5mm) outline and 7 9 741 3 6 mechanical data
revision history lis244al 14/15 6 revision history table 7. document revision history date revision changes 29-jun-2007 1 initial release
lis244al 15/15 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 he rein at any time, without notice. all st products are sold pursuant to st?s terms and conditions of sale. purchasers are solely responsible for the choice, selection and use of the st products and services described herein, and st as sumes no liability whatsoever relating to the choice, selection or use of the st products and services described herein. no license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. i f any part of this document refers to any third party products or services it shall not be deemed a license grant by st for the use of such third party products or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoev er of such third party products or services or any intellectual property contained therein. unless otherwise set forth in st?s terms and conditions of sale st disclaims any express or implied warranty with respect to the use and/or sale of st products including without limitation implied warranties of merchantability, fitness for a parti cular purpose (and their equivalents under the laws of any jurisdiction), or infringement of any patent, copyright or other intellectual property right. unless expressly approved in writing by an authorized st representative, st products are not recommended, authorized or warranted for use in milita ry, air craft, space, life saving, or life sustaining applications, nor in products or systems where failure or malfunction may result in personal injury, death, or severe property or environmental damage. st products which are not specified as "automotive grade" may only be used in automotive applications at user?s own risk. resale of st products with provisions different from the statements and/or technical features set forth in this document shall immediately void any warranty granted by st for the st product or service described herein and shall not create or extend in any manner whatsoev er, any liability of st. st and the st logo are trademarks or registered trademarks of st in various countries. information in this document supersedes and replaces all information previously supplied. the st logo is a registered trademark of stmicroelectronics. all other names are the property of their respective owners. ? 2007 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com

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