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small, low power, 3-axis 3 g accelerometer ADXL337 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 rights 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 ?2010 analog devices, inc. all rights reserved. features 3-axis sensing small, low profile package 3 mm 3 mm 1.45 mm lfcsp low power: 300 a (typical) single-supply operation: 1.8 v to 3.6 v 10,000 g shock survival excellent temperature stability bandwidth adjustment with a single capacitor per axis rohs/weee and lead-free compliant applications cost-sensitive, low power, motion- and tilt-sensing applications mobile devices gaming systems disk drive protection image stabilization sports and health devices general description the ADXL337 is a small, thin, low power, complete 3-axis accelerometer with signal conditioned voltage outputs. the product measures acceleration with a minimum full-scale range of 3 g . it can measure the static acceleration of gravity in tilt- sensing applications, as well as dynamic acceleration resulting from motion, shock, or vibration. the user selects the bandwidth of the accelerometer using the c x , c y , and c z capacitors at the x out , y out , and z out pins. bandwidths can be selected to suit the application, with a range of 0.5 hz to 1600 hz for x and y axes and a range of 0.5 hz to 550 hz for the z axis. the ADXL337 is available in a small, low profile, 3 mm 3 mm 1.45 mm, 16-lead, lead frame chip scale package (lfcsp_lq). functional block diagram ADXL337 3-axis sensor demodulator output amplifiers ac amplifier gnd st +3 v ~32k ? x out c x c y c z y out c dc v s z out ~32k ? ~32k ? 09358-001 figure 1.
ADXL337 rev. 0 | page 2 of 16 table of contents features .............................................................................................. 1 applications ....................................................................................... 1 general description ......................................................................... 1 functional block diagram .............................................................. 1 revision history ............................................................................... 2 specifications ..................................................................................... 3 absolute maximum ratings ............................................................ 4 esd caution .................................................................................. 4 pin configuration and function descriptions ............................. 5 typical performance characteristics ............................................. 6 theory of operation ...................................................................... 10 mechanical sensor ...................................................................... 10 performance ................................................................................ 10 applications information .............................................................. 11 power supply decoupling ......................................................... 11 setting the bandwidth using c x , c y , and c z .......................... 11 self test ........................................................................................ 11 design trade-offs for selecting filter characteristics: the noise/bw trade-off .................................................................. 11 use with operating voltages other than 3 v ............................ 12 axes of acceleration sensitivity ............................................... 12 layout and design recommendations ................................... 13 outline dimensions ....................................................................... 14 ordering guide .......................................................................... 14 revision history 10/10revision 0: initial version
ADXL337 rev. 0 | page 3 of 16 specifications t a = 25c, v s = 3 v, c x = c y = c z = 0.1 f, acceleration = 0 g , unless otherwise noted. all minimum and maximum specifications are guaranteed. typical specifications are not guaranteed. table 1. parameter test conditions/comments min typ max unit sensor input each axis measurement range 3 3.6 g nonlinearity % of full scale 0.3 % package alignment error 1 degrees interaxis alignment error 0.1 degrees cross-axis sensitivity 1 1 % sensitivity (ratiometric) 2 each axis sensitivity at x out , y out , z out v s = 3 v 270 300 330 mv/g sensitivity change due to temperature 3 v s = 3 v 0.01 %/c 0 g bias level (ratiometric) 0 g voltage at x out , y out v s = 3 v 1.35 1.5 1.65 v 0 g voltage at z out v s = 3 v 1.2 1.5 1.8 v 0 g offset vs. temperature x out , y out 1.1 mg /c 0 g offset vs. temperature z out 1.6 mg /c noise performance noise density x out , y out 175 g /hz rms noise density z out 300 g /hz rms frequency response 4 bandwidth x out , y out 5 no external filter 1600 hz bandwidth z out 5 no external filter 550 hz r filt tolerance 32 15% k sensor resonant frequency 5.5 khz self test 6 logic input low 0.6 v logic input high 2.4 v st actuation current 60 a output change at x out self test 0 to 1 ?150 ?325 ?600 mv output change at y out self test 0 to 1 +150 +325 +600 mv output change at z out self test 0 to 1 +150 +550 +1000 mv output amplifier output swing low no load 0.1 v output swing high no load 2.8 v power supply operating voltage range 7 1.8 3.0 3.6 v supply current v s = 3 v 300 a turn-on time 8 no external filter 1 ms temperature operating temperature range ?40 +85 c 1 defined as coupling between any two axes. 2 sensitivity is essentially ratiometric to v s . 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 filter capacitors (c x , c y , c z ). 5 bandwidth with external capacitors = 1/(2 32 k c). for c x , c y = 0.003 f, bandwidth = 1.6 khz. for c z = 0.01 f, bandwidth = 500 hz. for c x , c y , c z = 10 f, bandwidth = 0.5 hz. 6 self test response changes cubically with v s . 7 tested at 3.0 v and guaranteed by design only (not tested) to work over the full range from 1.8 v to 3.6 v. 8 turn-on time is dependent on c x , c y , c z and is approximately 160 (c x or c y or c z ) + 1, where c x , c y , and c z are in f and the resulting turn-on time is in ms.
ADXL337 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 +3.6 v all other pins (gnd ? 0.3 v) to (v s + 0.3 v) output short-circuit duration (any pin to common) indefinite temperature range (powered) ?55c to +125c temperature range (storage) ?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
ADXL337 rev. 0 | page 5 of 16 pin configuration and fu nction descriptions res 1 st 2 res 3 y out 4 nc 12 nc 11 nc 10 nc 9 x out gnd gnd nc 5678 16 z out 15 v s 14 v s 13 nc ADXL337 top view (not to scale) +z +x +y 09358-003 notes 1. nc = no connect. 2 . exposed pad is not internally connected but should be soldered for mechanical integrity. figure 2. pin configuration table 3. pin function descriptions pin no. mnemonic description 1, 3 res reserved. this pin must be connected to gnd or left open. 2 st self test. 4 y out y channel output. 5 x out x channel output. 6, 7 gnd must be connected to ground. 8 to 13 nc not internally connected. 14 v s supply voltage (3.0 v typical). 15 v s supply voltage (3.0 v typical). 16 z out z channel output. epad exposed pad. not internally connected but should be soldered for mechanical integrity.
ADXL337 rev. 0 | page 6 of 16 typical performance characteristics n > 250 for all typical performance plots, unless otherwise noted. (n is the number of parts tested and used to produce the his tograms.) 0 5 10 15 20 25 1.40 1.41 1.42 1.43 1.44 1.45 1.46 1.47 1.48 1.49 1.50 1.51 1.52 1.53 1.54 1.55 1.56 1.57 1.58 1.59 1.60 percent of popul a tion output (v) 09358-005 figure 3. x-axis zero g bias at 25c, v s = 3 v 0 5 10 15 20 25 1.40 1.41 1.42 1.43 1.44 1.45 1.46 1.47 1.48 1.49 1.50 1.51 1.52 1.53 1.54 1.55 1.56 1.57 1.58 1.59 1.60 percent of popul a tion output (v) 09358-006 figure 4. y-axis zero g bias at 25c, v s = 3 v 0 2 4 6 8 10 12 14 16 18 percent of popul a tion 1.40 1.41 1.42 1.43 1.44 1.45 1.46 1.47 1.48 1.49 1.50 1.51 1.52 1.53 1.54 1.55 1.56 1.57 1.58 1.59 1.60 output (v) 09358-007 figure 5. z-axis zero g bias at 25c, v s = 3 v 0 5 10 15 20 25 30 35 40 45 ?0.35 ?0.34 ?0.33 ?0.32 ?0.31 ?0.30 ?0.29 ?0.28 ?0.27 ?0.26 ?0.25 percent of popul a tion output change due to self test (v) 0 9358-008 figure 6. x-axis self-test response at 25c, v s = 3 v output change due to self test (v) 0 5 10 15 20 25 30 35 40 45 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 percent of popul a tion 09358-009 figure 7. y-axis self-test response at 25c, v s = 3 v 0 10 20 30 40 50 60 0.44 0.46 0.48 0.50 0.52 0.54 0.56 0.58 0.60 0.62 0.64 output change due to self test (v) percent of popul a tion 0 9358-010 figure 8. z-axis self-test response at 25c, v s = 3 v
ADXL337 rev. 0 | page 7 of 16 0 5 10 15 20 25 30 35 40 45 ?2.50 ?2.25 ?2.00 ?1.75 ?1.50 ?1.25 ?1.00 ?0.75 ?0.50 ?0.25 0 0.25 0.50 0.75 1.00 percent of popul a tion temperature coefficient (m g /c) 09358-011 figure 9. x-axis zero g bias temperature coefficient, v s = 3 v 0 5 10 15 20 25 30 35 ?2.50 ?2.25 ?2.00 ?1.75 ?1.50 ?1.25 ?1.00 ?0.75 ?0.50 ?0.25 0 0.25 0.50 0.75 1.00 percent of popul a tion temperature coefficient (m g /c) 09358-012 figure 10. y-axis zero g bias temperature coefficient, v s = 3 v 0 5 10 15 20 25 30 percent of popul a tion temperature coefficient (m g /c) 0 9358-013 ?3.0 ?2.5 ?2.0 ?1.5 ?1.0 ?0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 figure 11. z-axis zero g bias temperature coefficient, v s = 3 v 1.40 1.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58 1.60 ?40 ?20 0 20 40 60 80 100 output (v) temperature (c) 09358-014 figure 12. x-axis zero g bias vs. temperatureeight parts soldered to pcb 1.40 1.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58 1.60 ?40 ?20 0 20 40 60 80 100 output (v) temperature (c) 09358-015 figure 13. y-axis zero g bias vs. temperatureeight parts soldered to pcb 1.40 1.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58 1.60 ?60 ?40 ?20 0 20 40 60 80 100 output (v) temperature (c) 09358-016 figure 14. z-axis zero g bias vs. temperatureeight parts soldered to pcb
ADXL337 rev. 0 | page 8 of 16 0 5 10 15 20 25 30 35 40 45 50 0.290 0.293 0.296 0.299 0.302 0.305 0.308 0.311 0.314 0.317 percent of popul a tion sensitivity (v/ g ) 09358-017 figure 15. x-axis sensitivity at 25c, v s = 3 v 0 10 20 30 40 50 60 0.290 0.293 0.296 0.299 0.302 0.305 0.308 0.311 0.314 0.317 0.320 percent of popul a tion sensitivity (v/ g ) 09358-018 figure 16. y-axis sensitivity at 25c, v s = 3 v 0 5 10 15 20 25 30 35 40 45 50 0.290 0.293 0.296 0.299 0.302 0.305 0.308 0.311 0.314 0.317 0.320 percent of popul a tion sensitivity (v/ g ) 09358-019 figure 17. z-axis sensitivity at 25c, v s = 3 v 0.27 0.28 0.29 0.30 0.31 0.32 0.33 ?40 ?20 0 20 40 60 80 100 sensitivity (v/ g ) temperature (c) 09358-020 figure 18. x-axis sensitivity vs. temperature, eight parts soldered to pcb, v s = 3 v 0.27 0.28 0.29 0.30 0.31 0.32 0.33 ?40 ?20 0 20 40 60 80 100 sensitivity (v/ g ) temperature (c) 09358-021 figure 19. y-axis sensitivity vs. temperature, eight parts soldered to pcb, v s = 3 v 0.27 0.28 0.29 0.30 0.31 0.32 0.33 ?40 ?20 0 sensitivity (v/ g ) temperature (c) 09358-022 20 40 60 80 100 figure 20. z-axis sensitivity vs. temperature, eight parts soldered to pcb, v s = 3 v
ADXL337 rev. 0 | page 9 of 16 0 50 100 150 200 250 300 350 400 1.5 2.0 2.5 3.0 3.5 4.0 current (a) supply voltage (v) 09358-023 figure 21. typical current co nsumption vs. supply voltage 09358-024 time (1ms/div) power, 1v/div y out , 500mv/div x out , 500mv/div c x = c y = c z = 0.001f z out , 500mv/div outputs are offset for clarity figure 22. typical turn-on time, v s = 3 v
ADXL337 rev. 0 | page 10 of 16 theory of operation the ADXL337 is a complete 3-axis acceleration measurement system. the ADXL337 has a measurement range of 3 g minimum. 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 can measure the static acceleration of gravity in tilt-sensing applications as well as dynamic acceleration resulting from motion, shock, or vibration. 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 moving mass and unbalances the differential capacitor resulting in a sensor output whose amplitude is proportional to acceleration. phase-sensitive demodulation techniques are then used to determine the magnitude and direction of the acceleration. the demodulator output is amplified and brought off chip through a 32 k resistor. the user then sets the signal bandwidth (bw) of the device by adding a capacitor. this filtering improves measurement resolution and helps prevent aliasing. mechanical sensor the ADXL337 uses a single structure for sensing the x, y, and z axes. as a result, the three axes sense directions are highly orthogonal with little cross-axis sensitivity. mechanical misalignment of the sensor die to the package is the chief source of cross-axis sensitivity. mechanical misalignment can be calibrated out at the system level. performance rather than using additional temperature compensation circuitry, innovative design techniques ensure that high performance is built into the ADXL337. 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 ?25c to +85c temperature range).
ADXL337 rev. 0 | page 11 of 16 applications information power supply decoupling for most applications, a single 0.1 f capacitor, c dc , placed close to the ADXL337 supply pins adequately decouples the accelerometer from noise on the power supply. however, in applications where noise is present at the 50 khz internal clock frequency (or any harmonic thereof), additional care in power supply bypassing is required because this noise can cause errors in acceleration measurement. 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 (1 f or greater) can be added in parallel to c dc . ensure that the connection from the ADXL337 ground to the power supply ground is low impedance because noise transmitted through ground has a similar effect as noise transmitted through v s . setting the bandwidth using c x , c y , and c z the ADXL337 has provisions for band limiting the x out , y out , and z 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, z ) ) or more simply f C3 db = 5 f/ c ( x , y, z ) 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 0.0047 f for c x , c y , and c z is recommended in all cases. table 4. filter capacitor selection, c x , c y , and c z 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 ?1.08 g (corresponding to ?325 mv) in the x-axis, +1.08 g (or +325 mv) on the y-axis, and +1.83 m g (or +550 mv) on the z-axis. this st pin can be left open circuit or connected to common (gnd) in normal use. never expose the st pin 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 selected accelerometer bandwidth ultimately determines the measurement resolution (smallest detectable acceleration). filtering can be used to lower the noise floor to improve the resolution of the accelerometer. resolution is dependent on the analog filter bandwidth at x out , y out , and z out . the output of the ADXL337 has a typical bandwidth of greater than 500 hz. the user must filter the signal at this point to limit aliasing errors. the analog bandwidth must be no more than half the analog-to-digital sampling frequency to minimize aliasing. the analog bandwidth can be decreased further to reduce noise and improve resolution. the ADXL337 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 accelerometer bandwidth). the user should limit bandwidth to the lowest frequency needed by the application to maximize the resolution and dynamic range of the accelerometer. with the single-pole, roll-off characteristic, the typical noise of the ADXL337 is determined by rms noise = noise density )1.6( bw it is often useful to know the peak value of the noise. peak-to-peak noise can only be estimated by statistical methods. table 5 is useful for estimating the probabilities of exceeding various peak values, given the rms value. table 5. estimation of peak-to-peak noise peak-to-peak value percent 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
ADXL337 rev. 0 | page 12 of 16 use with operating voltages other than 3 v the ADXL337 is tested and specified at v s = 3 v; however, it can be powered with v s as low as 1.8 v or as high as 3.6 v. note that some performance parameters change as the supply voltage is varied. the ADXL337 output is ratiometric; therefore, the output sensitivity (or scale factor) varies proportionally to the supply voltage. at v s = 3.6 v, the output sensitivity is typically 360 mv/ g . at v s = 2 v, the output sensitivity is typically 195 mv/ g . the zero g bias output is also ratiometric; therefore, 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 = 3.6 v, the x- and y-axis noise density is typically 120 g /hz, and at v s = 2 v, the x- and y-axis noise density is typically 270 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 = 3.6 v, the self test response for the ADXL337 is approximately ?560 mv for the x-axis, +560 mv for the y-axis, and +950 mv for the z-axis. at v s = 2 v, the self test response is approximately ?96 mv for the x-axis, +96 mv for the y-axis, and ?163 mv for the z-axis. the supply current decreases as the supply voltage decreases. typical current consumption at v s = 3.6 v is 375 a, and typical current consumption at v s = 2 v is 200 a. axes of acceleration sensitivity the axes of sensitivity for the accelerometer are shown in figure 23 , and figure 24 shows the output response when the accelerometer is oriented parallel to each of these axes. a z a y a x t o p 09358-030 figure 23. axes of acceleration sensitivity, corresponding output voltage increases when accelerated along the sensitive axis x out = ?1 g y out = 0 g z out = 0 g gravity x out = 0 g y out = 1 g z out = 0 g x out = 0 g y out = ?1 g z out = 0 g x out = 1 g y out = 0 g z out = 0 g x out = 0 g y out = 0 g z out = 1 g x out = 0 g y out = 0 g z out = ?1 g top top top top t o p 09358-031 figure 24. output response vs. orientation to gravity
ADXL337 rev. 0 | page 13 of 16 layout and design recommendations the recommended soldering profile is shown in figure 25 followed by a description of the profile features in table 6 . the recommended pcb layout or solder land drawing is shown in figure 26 . t p t l t 25c t s preheat critical zone t l to t p temperature time ramp-down ramp-up t smin t smax t p t l 09358-002 figure 25. recommended soldering profile table 6. recommended soldering profile profile feature sn63/pb37 pb-free average ramp rate (t l to t p ) 3c/sec maximum 3c/sec maximum preheat minimum temperature (t smin ) 100c 150c maximum temperature (t smax ) 150c 200c time (t smin to t smax ), t s 60 sec to 120 sec 60 sec to 180 sec t smax to t l ramp-up rate 3c/sec maximum 3c/sec maximum time maintained above liquidous (t l ) liquidous temperature (t l ) 183c 217c time (t l ) 60 sec to 150 sec 60 sec to 150 sec peak temperature (t p ) 240c + 0c/?5c 260c + 0c/?5c time within 5c of actual peak temperature (t p ) 10 sec to 30 sec 20 sec to 40 sec ramp-down rate 6c/sec maximum 6c/sec maximum time 25c to peak temperature (t 25c ) 6 minutes maximum 8 minutes maximum c enter pad is not internally connected but should be soldered for mechanical integrity 0.40 max 0.50 0.25 1.60 0.50 0.25 3 3 0.25 max 1.60 dimensions shown in millimeters 09358-004 figure 26. recommended pcb layout
ADXL337 rev. 0 | page 14 of 16 outline dimensions 3.10 3.00 sq 2.90 0.30 0.25 0.18 1.70 1.60 sq 1.50 1 0.50 bsc bottom view top view 16 5 8 9 12 13 4 exposed pad p i n 1 i n d i c a t o r 0.45 0.40 0.35 seating plane 0.05 max 0.02 nom 0.152 ref 0.20 min coplanarity 0.08 pin 1 indicator 1.50 1.45 1.40 forproperconnectionof the exposed pad, refer to the pin configuration and function descriptions section of this data sheet. 04-27-2010-a figure 27. 16-lead lead frame chip scale package [lfcsp_lq] 3 mm 3 mm body, thick quad (cp-16-28) dimensions shown in millimeters ordering guide model 1 measurement range specified voltage temperat ure range package description package option ADXL337bcpzCrl 3 g 3 v ?40c to +85c 16-lead lfcsp_lq cp-16-28 ADXL337bcpzCrl7 3 g 3 v ?40c to +85c 16-lead lfcsp_lq cp-16-28 eval-ADXL337z evaluation board 1 z = rohs compliant part.
ADXL337 rev. 0 | page 15 of 16 notes
ADXL337 rev. 0 | page 16 of 16 notes ?2010 analog devices, inc. all rights reserved. trademarks and registered trademarks are the prop erty of their respective owners. d09358-0-10/10(0)

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