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small and thin 5 g imems ? accelerometer adxl320 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: 781.326.8703 ? 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 5.25 v low power: 350 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 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 adxl320 is a low cost, low power, complete dual-axis accelerometer with signal conditioned voltage outputs, which is all on a single monolithic ic. the product measures acceleration with a full-scale range of 5 g (typical). it can also measure both dynamic acceleration (vibration) and static acceleration (gravity). the adxl320s typical noise floor is 250 g /hz, allowing 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 may be selected to suit the application. the adxl320 is available in a very thin 4 mm 4 mm 1.45 mm, 16-lead, plastic lfcsp. functional block diagram 04993-001 adxl320 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.
adxl320 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 9/04revision 0: initial version
adxl320 rev. 0 | page 3 of 16 specifications 1 t a = 25c, v s = 3 v, c x = c y = 0.1 f, acceleration = 0 g , unless otherwise noted. table 1. parameter conditions min typ max unit sensor input each axis measurement range 5 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 156 174 192 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 0 g offset versus temperature 0.6 m g /c noise performance noise density @ 25c 250 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 55 mv output amplifier output swing low no load 0.3 v output swing high no load 2.5 v power supply operating voltage range 2.4 5.25 v quiescent supply current 0.48 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 154 mv/v/ g to 194 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.
adxl320 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. althou gh 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.
adxl320 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 adxl320 top view (not to scale) 04993-022 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 5.25 v 15 v s 2.4 v to 5.25 v 16 nc do not connect
adxl320 rev. 0 | page 6 of 16 04993-002 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 3. recommended soldering profile table 4. recommended soldering profile profile feature sn63/pb37 pb-free average ramp rate (t l to t p ) 3c/second max 3c/second max preheat minimum temperature (t smin ) 100c 150c maximum temperature (t smax ) 150c 200c time (t smin to t smax ), t s 60 ? 120 seconds 60 ? 150 seconds t smax to t l ramp-up rate 3c/second 3c/second time maintained above liquidous (t l ) liquidous temperature (t l ) 183c 217c time (t l ) 60 ? 150 seconds 60 ? 150 seconds peak temperature (t p ) 240c + 0c/?5c 260c + 0c/?5c time within 5c of actual peak temperature (t p ) 10 ? 30 seconds 20 ? 40 seconds ramp-down rate 6c/second max 6c/second max time 25c to peak temperature 6 minutes max 8 minutes max
adxl320 rev. 0 | page 7 of 16 typical performance characteristics (v s = 3.0 v) 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 04993-003 output (v) % of population figure 4. x-axis zero g bias deviation from ideal at 25c 35 0 5 10 15 20 25 30 ?2.8?2.4 ?2.0 ?1.6?1.2 ?0.8 ?0.4 0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 04993-004 temperature coefficient (m g / c) % of population figure 5. x-axis zero g bias temperature coefficient 90 0 10 20 30 40 50 70 80 60 164 184182180178176174172170168166 04993-005 sensitivity (mv/ g ) % of population figure 6. x-axis sensitivity at 25c 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 04993-006 output (v) % of population figure 7. y-axis zero g bias deviation from ideal at 25c 35 0 5 10 15 20 25 30 ?2.8?2.4 ?2.0 ?1.6?1.2 ?0.8 ?0.4 0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 04993-007 temperature coefficient (m g / c) % of population figure 8. y-axis zero g bias temperature coefficient 70 0 10 20 30 40 50 60 164 184182180178176174172170168166 04993-008 sensitivity (mv/ g ) % of population figure 9. y-axis sensitivity at 25c
adxl320 rev. 0 | page 8 of 16 1.54 1.53 1.52 1.51 1.50 1.49 1.48 1.47 1.46 ?30 ?20 ?10 0 10 20 30 40 50 60 70 80 04993-009 temperature ( c) output (scale = 174mv/ g ) figure 10. zero g bias vs. temperatureparts soldered to pcb 35 30 25 20 15 10 5 0 170 190 210 230 250 270 290 310 330 350 04993-010 noise ug / hz % of population figure 11. x-axis noise density at 25c 25 20 15 10 5 0 ?5?4?3?2?1012345 04993-011 percent sensitivity (%) % of population figure 12. z vs. x cross-axis sensitivity 0.180 0.170 0.171 0.172 0.173 0.174 0.175 0.176 0.177 0.178 0.179 ?30 ?20 ?10 0 10 20 30 40 50 60 70 80 04993-012 temperature ( c) sensitivity (v/ g ) figure 13. sensitivity vs. temperatureparts soldered to pcb 30 25 20 15 10 5 0 170 190 210 230 250 270 290 310 330 350 04993-013 noise ug / hz % of population figure 14. y-axis noise density at 25c 30 25 20 15 10 5 0 ?5?4?3?2?1012345 04993-014 percent sensitivity (%) % of population figure 15. z vs. y cross-axis sensitivity
adxl320 rev. 0 | page 9 of 16 60 50 40 30 20 10 0 35 7570656055504540 04993-015 self-test (mv) % of population figure 16. x-axis self-test response at 25c 40 35 30 25 20 15 10 5 0 420 430 440 450 460 470 480 490 500 510 520 530 04993-016 current ( a) % of population figure 17. supply current at 25c 60 50 40 30 20 10 0 35 7570656055504540 04993-017 self-test (mv) % of population figure 18. y-axis self-test response at 25c 04993-020 figure 19. turn-on timec x , c y = 0.1 f, time scale = 2 ms/div
adxl320 rev. 0 | page 10 of 16 04993-018 x out = 1.500v y out = 1.500v x out = 1.500v y out = 1.326v x out = 1.326v y out = 1.500v x out = 1.674v y out = 1.50v x out = 1.500v y out = 1.674v earth's surface xl 320j #1234 5678p xl 320j #1234 5678p xl 320j #1234 5678p xl 320j #1234 5678p figure 20. output response vs. orientation
adxl320 rev. 0 | page 11 of 16 theory of operation the adxl320 is a complete acceleration measurement system on a single monolithic ic. the adxl320 has a measurement range of 5 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 independent 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 have been used to ensure high performance is built-in. as a result, there is neither quantization error nor nonmonotonic behavior, and temperature hysteresis is very low (typically less than 3 m g over the ?20c to +70c temperature range). figure 10 shows the zero g output performance of eight parts (x- and y-axis) over a ?20c to +70c temperature range. figure 13 demonstrates the typical sensitivity shift over temperature for supply voltages of 3 v. this is typically better than 1% over the ?20c to +70c temperature range.
adxl320 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 may cause interference on the adxl320 output. if additional decoupling is needed, a 100 (or smaller) resistor or ferrite bead may be inserted in the supply line. additionally, a larger bulk bypass capacitor (in the 1 f to 4.7 f range) may be added in parallel to c dc . setting the bandwidth using c x and c y the adxl320 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 315 m g (corresponding to 55 mv). this pin may 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 adxl320 has a typical bandwidth of 2.5 khz. the user must filter the signal at this point to limit aliasing errors. the analog bandwidth must be no more than half the a/d sampling frequency to minimize aliasing. the analog bandwidth may be further decreased to reduce noise and improve resolution. the adxl320 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 application in order to maximize the resolution and dynamic range of the accelerometer. with the single-pole, roll-off characteristic, the typical noise of the adxl320 is determined by )1.6()g/(250 = bwhz rmsnoise at 100 hz bandwidth the noise will be mg3.2)1.6100()g/(250 = = hz 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
adxl320 rev. 0 | page 13 of 16 peak-to-peak noise values give the best estimate of the uncertainty in a single measurement. table 7 gives the typical noise output of the adxl320 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 (mg) 10 0.47 1.0 6 50 0.1 2.25 13.5 100 0.047 3.2 18.9 500 0.01 7.1 42.8 use with operating voltages other than 3 v the adxl320 is tested and specified at v s = 3 v; however, it can be powered with v s as low as 2.4 v or as high as 5.25 v. note that some performance parameters change as the supply voltage is varied. the adxl320 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 312 mv/ g . at v s = 2.4 v, the output sensitivity is typically 135 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 adxl320 is approximately 250 mv. at v s = 2.4 v, the self-test response is approximately 25 mv. the supply current decreases as the supply voltage decreases. typical current consumption at v s = 5 v is 750 a, and typical current consumption at v s = 2.4 v is 350 a. use as a dual-axis tilt sensor tilt measurement is one of the adxl320s 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 it is parallel to the earths surface). at this orientation, its 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 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.
adxl320 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 21. 16-lead lead frame chip scale package [lfcsp_lq] 4 mm 4 mm body (cp-16-5a*) dimensions shown in millimeters ordering guide model measurement range specified voltage (v) temperature range package description package option adxl320jcp 1 5 g 3 ?20c to +70c 16-lead lfcsp_lq cp-16-5a adxl320jcpCreel 1 5 g 3 ?20c to +70c 16-lead lfcsp_lq cp-16-5a adxl320jcpCreel7 1 5 g 3 ?20c to +70c 16-lead lfcsp_lq cp-16-5a adxl320eb evaluation board 1 lead finishmatte tin.
adxl320 rev. 0 | page 15 of 16 notes
adxl320 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. d04993C0C6/07(0)

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