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small and thin 2 g accelerometer adxl322 rev. 0 information furnished by analog devices is believed to be accurate and reliable. however, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. specifications subject to change without notice. no license is granted by implication or otherwise under any patent or patent ri ghts of analog devices. trademarks and registered trademarks are the property of their respective owners. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781.329.4700 www.analog.com fax: 781.461.3113 ? 2007 analog devices, inc. all rights reserved. features small and thin 4 mm 4 mm 1.45 mm lfcsp package 2 m g resolution at 60 hz wide supply voltage range: 2.4 v to 6 v low power: 340 a at v s = 2.4 v (typ) good zero g bias stability good sensitivity accuracy x-axis and y-axis aligned to within 0.1 (typ) bw adjustment with a single capacitor single-supply operation 10,000 g shock survival pb free: compatible with sn/pb and pb-free solder processes applications cost-sensitive motion- and tilt-sensing applications smart hand-held devices mobile phones sports and health-related devices pc security and pc peripherals general description the adxl322 is a small, thin, low power, complete, dual-axis accelerometer with signal conditioned voltage outputs, which are all on a single monolithic ic. the product measures accel- eration with a full-scale range of 2 g (typical). it can also measure both dynamic acceleration (vibration) and static acceleration (gravity). the adxl322s typical noise floor is 220 g /hz, which allows signals below 2 m g to be resolved in tilt-sensing applications using narrow bandwidths (<60 hz). the user selects the bandwidth of the accelerometer using capacitors c x and c y at the x out and y out pins. bandwidths of 0.5 hz to 2.5 khz can be selected to suit the application. the adxl322 is available in a 4 mm 4 mm 1.45 mm, 16-lead, plastic lfcsp. functional block diagram 05589-001 adxl322 sensor +3v output amp output amp com st v s c dc demod ac amp r filt 32k x out c x y out c y r filt 32k figure 1.
adxl322 rev. 0 | page 2 of 16 table of contents specifications ..................................................................................... 3 absolute maximum ratings ............................................................ 4 esd caution .................................................................................. 4 pin configuration and function descriptions ............................. 5 typical performance characteristics (v s = 3.0 v) ....................... 7 theory of operation ...................................................................... 11 performance ................................................................................ 11 applications ..................................................................................... 12 power supply decoupling ......................................................... 12 setting the bandwidth using c x and c y ................................. 12 self-test ....................................................................................... 12 design trade-offs for selecting filter characteristics: the noise/bw trade-off .................................................................. 12 use with operating voltages other than 3 v ............................. 13 use as a dual-axis tilt sensor ................................................. 13 outline dimensions ....................................................................... 14 ordering guide .......................................................................... 14 revision history 6/05 revision 0: initial version
adxl322 rev. 0 | page 3 of 16 specifications t a = 25c, v s = 3 v, c x = c y = 0.1 f, acceleration = 0 g , unless otherwise noted 1 . table 1. parameter conditions min typ max unit sensor input each axis measurement range 2 g nonlinearity % of full scale 0.2 % package alignment error 1 degrees alignment error x sensor to y sensor 0.1 degrees cross-axis sensitivity 2 % sensitivity (ratiometric) 2 each axis sensitivity at x out , y out v s = 3 v 378 420 462 mv/ g sensitivity change due to temperature 3 v s = 3 v 0.01 %/c zero g bias level (ratiometric) each axis 0 g voltage at x out , y out v s = 3 v 1.3 1.5 1.7 v initial 0 g bias deviation from ideal 50 m g 0 g offset vs. temperature <0.5 m g /c noise performance noise density at 25c 220 g /hz rms frequency response 4 c x , c y range 5 0.002 10 f r filt tolerance 32 15% k sensor resonant frequency 5.5 khz self-test t 6 logic input low 0.6 v logic input high 2.4 v st input resistance to ground 50 k output change at x out , y out self-test 0 to 1 125 mv output amplifier output swing low no load 0.2 v output swing high no load 2.7 v power supply operating voltage range 2.4 6 v quiescent supply current 0.45 ma turn-on time 7 20 ms temperature operating temperature range ?20 70 c 1 all minimum and maximum specifications are guarante ed. typical specifications are not guaranteed. 2 sensitivity is essentially ratiometric to v s . for v s = 2.7 v to 3.3 v, se nsitivity is 138 mv/v/ g to 142 mv/v/ g typical. 3 defined as the output change from ambient-to-maximum temperature or ambient-to-minimum temperature. 4 actual frequency response controlled by user-supplied external capacitor (c x , c y ). 5 bandwidth = 1/(2 32 k c). for c x , c y = 0.002 f, bandwidth = 2500 hz. for c x , c y = 10 f, bandwidth = 0.5 hz. minimum/maximum values are not tested. 6 self-test response changes cubically with v s . 7 larger values of c x , c y increase turn-on time. turn-o n time is approximately 160 c x or c y + 4 ms, where c x , c y are in f.
adxl322 rev. 0 | page 4 of 16 absolute maximum ratings table 2. parameter rating acceleration (any axis, unpowered) 10,000 g acceleration (any axis, powered) 10,000 g v s ?0.3 v to +7.0 v all other pins (com ? 0.3 v) to (v s + 0.3 v) output short-circuit duration (any pin to common) indefinite operating temperature range ?55c to +125c storage temperature ?65c to +150c stresses above those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. esd caution esd (electrostatic discharge) sensitive device. electr ostatic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge without detection. although this product features proprietary esd protection circuitry, permanent dama ge may occur on devices subjected to high energy electrostatic discharges. therefore, proper esd precautions are recommended to avoid performance degradation or loss of functionality.
adxl322 rev. 0 | page 5 of 16 pin configuration and fu nction descriptions nc x out st nc com y out nc nc com com com nc nc v s v s nc nc = no connec t adxl322 top view (not to scale) 05589-022 figure 2. pin configuration table 3. pin function descriptions pin no. mnemonic description 1 nc do not connect 2 st self-test 3 com common 4 nc do not connect 5 com common 6 com common 7 com common 8 nc do not connect 9 nc do not connect 10 y out y-channel output 11 nc do not connect 12 x out x-channel output 13 nc do not connect 14 v s 2.4 v to 6 v 15 v s 2.4 v to 6 v 16 nc do not connect 05589-023 0.600 max 0.350 max 1.950 0.325 4.000 4.000 1.950 0.325 0.650 0.650 figure 3. 4 mm 4 mm 16- pad lfcsp recommended pad layout
adxl322 rev. 0 | page 6 of 16 05589-002 t p t l t 25c to peak t s preheat critical zone t l to t p temperature time ramp-down ramp-up t smin t smax t p t l figure 4. recommended soldering profile table 4. recommended soldering profile profile feature sn63/pb37 pb-free average ramp rate (t l to t p ) 3c/sec max 3c/sec max preheat minimum temperature (t smin ) 100c 150c minimum temperature (t smax ) 150c 200c time (t smin to t smax ), t s 60 sec ? 120 sec 60 sec ? 150 sec t smax to t l ramp-up rate 3c/sec 3c/sec time maintained above liquidous (t l ) liquidous temperature (t l ) 183c 217c time (t l ) 60 sec ? 150 sec 60 sec ? 150 sec peak temperature (t p ) 240c + 0c/?5c 260c + 0c/?5c time within 5c of actual peak temperature (t p ) 10 sec ? 30 sec 20 sec ? 40 sec ramp-down rate 6c/sec max 6c/sec max time 25c to peak temperature 6 min max 8 min max
adxl322 rev. 0 | page 7 of 16 typical performance characteristics (v s = 3.0 v) 35 30 25 0 5 10 15 20 1.40 1.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58 1.60 05589-004 output (v) % of population figure 5. x-axis zero g bias at 25c 40 35 30 25 0 5 10 15 20 ?2.0 ?1.5 ?1.0 ?0.5 0 2.0 1.51.00.5 05589-005 temperature coefficient (m g / c) % of population figure 6. x-axis zero g bias temperature coefficient 50 40 45 35 30 25 0 5 10 15 20 0.400 0.405 0.410 0.415 0.420 0.425 0.430 0.435 0.440 0.445 0.450 05589-006 sensitivity (v/ g ) % of population figure 7. x-axis sensitivity at 25c 40 35 30 25 0 5 10 15 20 1.40 1.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58 1.60 05589-007 output (v) % of population figure 8. y-axis zero g bias at 25c 45 40 35 30 25 0 5 10 15 20 ?2.0 ?1.5 ?1.0 ?0.5 0 2.0 1.51.00.5 05589-008 temperature coefficient (m g / c) % of population figure 9. y-axis zero g bias temperature coefficient 45 40 35 30 25 0 5 10 15 20 0.400 0.405 0.410 0.415 0.420 0.425 0.430 0.435 0.440 0.445 0.450 05589-009 sensitivity (v/ g ) % of population figure 10. y-axis sensitivity at 25c
adxl322 rev. 0 | page 8 of 16 1.600 1.575 1.550 1.525 1.500 1.475 1.450 1.425 1.400 ?40 80 60 40 20 0 ?20 05589-010 temperature ( c) 0 g output (v) figure 11. zero g bias vs. temperatureparts soldered to pcb 70 60 50 40 30 20 10 0 150 160 170 180 190 200 210 220 230 240 250 05589-012 noise g / hz % of population figure 12. x-axis noise density at 25c 25 20 15 10 5 0 ?5?4?3?2?1012345 05589-011 percent sensitivity (%) % of population figure 13. z vs. x cross-axis sensitivity 0.440 0.435 0.430 0.425 0.420 0.415 0.410 0.405 0.400 ?40 80 60 40 20 0 ?20 05589-013 temperature ( c) sensitivity v/ g figure 14. sensitivity vs. temperatureparts soldered to pcb 45 40 35 30 25 20 15 10 5 0 150 160 170 180 190 200 210 220 230 240 250 05589-015 noise g / hz % of population figure 15. y-axis noise density at 25c 30 25 20 15 10 5 0 ?5?4?3?2?1012345 05589-014 percent sensitivity (%) % of population figure 16. z vs. y cross-axis sensitivity
adxl322 rev. 0 | page 9 of 16 25 20 15 10 5 0 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.16 05589-016 self-test (v) % of population figure 17. x-axis self-test response at 25c 60 50 40 30 20 10 0 350 370 390 410 430 450 470 490 05589-017 current ( a) % of population figure 18. supply current at 25c 25 20 15 10 5 0 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.16 05589-019 self-test (v) % of population figure 19. y-axis self-test response at 25c 05589-020 figure 20. turn-on timec x , c y = 0.1 f, time scale = 2 ms/div 550 500 450 400 350 300 ?40 ?20 0 20 40 60 80 100 120 05589-021 current ( a) temperature ( c) figure 21. supply current vs. temperature v s =3v
adxl322 rev. 0 | page 10 of 16 05589-018 x out = 1.500v y out = 1.500v x out = 1.50v y out = 1.08v x out = 1.08v y out = 1.50v x out = 1.92v y out = 1.50v x out = 1.50v y out = 1.92v earth's surface xl 322j #1234 5678p xl 322j #1234 5678p xl 322j #1234 5678p xl 322j #1234 5678p figure 22. output response vs. orientation
adxl322 rev. 0 | page 11 of 16 theory of operation the adxl322 is a complete acceleration measurement system on a single monolithic ic. the adxl322 has a measurement range of 2 g . it contains a polysilicon surface micromachined sensor and signal conditioning circuitry to implement an open- loop acceleration measurement architecture. the output signals are analog voltages that are proportional to acceleration. the accelerometer measures static acceleration forces, such as gravity, which allows it to be used as a tilt sensor. the sensor is a polysilicon surface-micromachined structure built on top of a silicon wafer. polysilicon springs suspend the structure over the surface of the wafer and provide a resistance against acceleration forces. deflection of the structure is measured using a differential capacitor that consists of inde- pendent fixed plates and plates attached to the moving mass. the fixed plates are driven by 180 out-of-phase square waves. acceleration deflects the beam and unbalances the differential capacitor, resulting in an output square wave whose amplitude is proportional to acceleration. phase-sensitive demodulation techniques are then used to rectify the signal and determine the direction of the acceleration. the demodulators output is amplified and brought off- chip through a 32 k resistor. the user then sets the signal bandwidth of the device by adding a capacitor. this filtering improves measurement resolution and helps prevent aliasing. performance rather than using additional temperature compensation circuitry, innovative design techniques were used to ensure built-in high performance. as a result, there is neither quanti- zation error nor nonmonotonic behavior, and temperature hysteresis is very low (typically less than 5 m g over the ?20c to +70c temperature range). figure 11 shows the zero g output performance of eight parts (x- and y-axis) over a ?20c to +70c temperature range. figure 14 demonstrates the typical sensitivity shift over tem- perature for supply voltages of 3 v. this is typically better than 1% over the ?20c to +70c temperature range.
adxl322 rev. 0 | page 12 of 16 applications power supply decoupling for most applications, a single 0.1 f capacitor, c dc , adequately decouples the accelerometer from noise on the power supply. however, in some cases, particularly where noise is present at the 140 khz internal clock frequency (or any harmonic thereof), noise on the supply can cause interference on the adxl322 output. if additional decoupling is needed, a 100 (or smaller) resistor or ferrite bead can be inserted in the supply line. additionally, a larger bulk bypass capacitor (in the 1 f to 4.7 f range) can be added in parallel to c dc . setting the bandwidth using c x and c y the adxl322 has provisions for band-limiting the x out and y out pins. capacitors must be added at these pins to implement low-pass filtering for antialiasing and noise reduction. the equation for the 3 db bandwidth is f ?3 db = 1/(2(32 k) c ( x , y ) ) or more simply, f C3 db = 5 f/ c ( x , y ) the tolerance of the internal resistor (r filt ) typically varies as much as 15% of its nominal value (32 k), and the bandwidth varies accordingly. a minimum capacitance of 2000 pf for c x and c y is required in all cases. table 5. filter capacitor selection, c x and c y bandwidth (hz) capacitor (f) 1 4.7 10 0.47 50 0.10 100 0.05 200 0.027 500 0.01 self-test the st pin controls the self-test feature. when this pin is set to v s , an electrostatic force is exerted on the accelerometer beam. the resulting movement of the beam allows the user to test if the accelerometer is functional. the typical change in output is 300 m g (corresponding to 125 mv). this pin can be left open- circuit or connected to common (com) in normal use. the st pin should never be exposed to voltages greater than v s + 0.3 v. if this cannot be guaranteed due to the system design (for instance, if there are multiple supply voltages), then a low v f clamping diode between st and v s is recommended. design trade-offs for selecting filter characteristics: the noise/bw trade-off the accelerometer bandwidth selected ultimately determines the measurement resolution (smallest detectable acceleration). filtering can be used to lower the noise floor, which improves the resolution of the accelerometer. resolution is dependent on the analog filter bandwidth at x out and y out . the output of the adxl322 has a typical bandwidth of 2.5 khz. to limit aliasing errors, the user must filter the signal at this point. the analog bandwidth must be no more than half the a/d sampling frequency to minimize aliasing. the analog bandwidth can be further decreased to reduce noise and improve resolution. the adxl322 noise has the characteristics of white gaussian noise, which contributes equally at all frequencies and is described in terms of g /hz (the noise is proportional to the square root of the accelerometers bandwidth). the user should limit bandwidth to the lowest frequency needed by the applica- tion in order to maximize the resolution and dynamic range of the accelerometer. with the single-pole, roll-off characteristic, the typical noise of the adxl322 is determined by )1.6bw()hzg/(220 = rmsnoise at 100 hz bandwidth the noise will be mg2.8)1.6100()hzg/(220 = = rmsnoise often, the peak value of the noise is desired. peak-to-peak noise can only be estimated by statistical methods. table 6 is useful for estimating the probabilities of exceeding various peak values, given the rms value. table 6. estimation of peak-to-peak noise peak-to-peak value % of time that noise exceeds nominal peak-to-peak value 2 rms 32 4 rms 4.6 6 rms 0.27 8 rms 0.006
adxl322 rev. 0 | page 13 of 16 peak-to-peak noise values give the best estimate of the uncer- tainty in a single measurement. table 7 gives the typical noise output of the adxl322 for various c x and c y values. table 7. filter capacitor selection (c x , c y ) bandwidth (hz) c x , c y (f) rms noise (m g ) peak-to-peak noise estimate (m g ) 10 0.47 0.9 5.3 50 0.1 2 11.8 100 0.047 2.8 16.7 500 0.01 6.2 37.3 use with operating voltages other than 3 v the adxl322 is tested and specified at v s = 3 v; however, this part can be powered with v s as low as 2.4 v or as high as 6 v. note that some performance parameters change as the supply voltage is varied. the adxl322 output is ratiometric, so the output sensitivity (or scale factor) varies proportionally to supply voltage. at v s = 5 v, the output sensitivity is typically 750 mv/ g . at v s = 2.4 v, the output sensitivity is typically 335 mv/ g . the zero g bias output is also ratiometric, so the zero g output is nominally equal to v s /2 at all supply voltages. the output noise is not ratiometric but is absolute in volts; therefore, the noise density decreases as the supply voltage increases. this is because the scale factor (mv/ g ) increases while the noise voltage remains constant. at v s = 5 v, the noise density is typically 150 g /hz, while at v s = 2.4 v, the noise density is typically 300 g /hz, self-test response in g is roughly proportional to the square of the supply voltage. however, when ratiometricity of sensitivity is factored in with supply voltage, the self-test response in volts is roughly proportional to the cube of the supply voltage. for example, at v s = 5 v, the self-test response for the adxl322 is approximately 610 mv. at v s = 2.4 v, the self-test response is approximately 59 mv. the supply current decreases as the supply voltage decreases. typical current consumption at v s = 5 v is 700 a, and typical current consumption at v s = 2.4 v is 340 a. use as a dual-axis tilt sensor tilt measurement is one of the adxl322s most popular applications. an accelerometer uses the force of gravity as an input vector to determine the orientation of an object in space. an accelerometer is most sensitive to tilt when its sensitive axis is perpendicular to the force of gravity (that is, when the pack- age is parallel to the earths surface). at this orientation, the accelerometers sensitivity to changes in tilt is highest. when the accelerometer is oriented on axis to gravity (near its +1 g or ?1 g reading), the change in output acceleration per degree of tilt is negligible. when the accelerometer is perpendicular to gravity, its output changes nearly 17.5 m g per degree of tilt. at 45, its output changes at only 12.2 m g per degree of tilt, and resolution declines. converting acceleration to tilt when the accelerometer is oriented so both its x-axis and y-axis are parallel to the earths surface, it can be used as a 2-axis tilt sensor with both a roll axis and a pitch axis. once the output signal from the accelerometer has been converted to an acceleration that varies between ?1 g and +1 g , the output tilt in degrees is calculated as pitch = asin ( a x /1 g ) roll = asin ( a y /1 g ) be sure to account for overranges. it is possible for the accelerometers to output a signal greater than 1 g due to vibration, shock, or other accelerations.
adxl322 rev. 0 | page 14 of 16 outline dimensions 16 5 13 8 9 12 1 4 0.65 bsc 2.43 1.75 sq 1.08 1.95 bsc 0.20 min pin 1 indicator bottom view 0.20 min seating plane 1.50 1.45 1.40 pin 1 indi c ator top view coplanarity 0.05 0.05 max 0.02 nom 0.35 0.30 0.25 0.55 0.50 0.45 4.15 4.00 sq 3.85 * stacked die with glass seal. 072606-a figure 23. 16-lead lead frame chip scale package [lfcsp_lq] 4 mm 4 mm body, thick quad (cp-16-5a*) dimensions shown in millimeters ordering guide model measurement range specified voltage (v) temperature range package description package option adxl322jcp 1 2 g 3 ?20c to +70c 16-lead lfcsp_lq cp-16-5a adxl322jcpCreel 1 2 g 3 ?20c to +70c 16-lead lfcsp_lq cp-16-5a adxl322eb evaluation board 1 lead finishmatte tin.
adxl322 rev. 0 | page 15 of 16 notes
adxl322 rev. 0 | page 16 of 16 notes ? 2007 analog devices, inc. all rights reserved. trademarks and registered trademarks are the prop erty of their respective owners. d05589C0C6/07(0)

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