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small, low power, 2-axis 3 g i mems ? accelerometer adxl323 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 ?2007 analog devices, inc. all rights reserved. features 2-axis sensing small, low-profile package 4 mm 4 mm 1.45 mm lfcsp_lq low power 180 a at v s = 1.8 v (typical) single-supply operation 1.8 v to 5.25 v 10,000 g shock survival excellent temperature stability bw adjustment with a single capacitor per axis rohs/weee 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 adxl323 is a small, thin, low power, complete 2-axis accelerometer with signal-conditioned voltage outputs, all on a single, monolithic ic. 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 and c y capacitors at the x out and y out pins. bandwidths can be selected to suit the application, with a range of 0.5 hz to 1600 hz. the adxl323 is available in a small, low profile, 4 mm 4 mm 1.45 mm, 16-lead, plastic lead frame chip scale package (lfcsp_lq). functional block diagram 2-axis sensor ac amp demod output amp output amp v s com st x out y out +3 v c x c y adxl323 r filt r filt c dc 06237-001 figure 1.
adxl323 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 ...................................................................... 11 mechanical sensor ...................................................................... 11 performance ................................................................................ 11 applications ..................................................................................... 12 power supply decoupling ......................................................... 12 setting the bandwidth using c x , c y , and c z .......................... 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 ........................... 12 axes of acceleration sensitivity ............................................... 13 outline dimensions ....................................................................... 14 ordering guide .......................................................................... 14 revision history 8/06revision 0: initial version
adxl323 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. all minimum and maximum specifications are guaranteed. typical specifications are not guaranteed. table 1. parameter conditions 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 inter-axis alignment error 0.1 degrees cross axis sensitivity 1 1 % sensitivity (ratiometric) 2 each axis sensitivity at x out , y out v s = 3 v 270 300 330 mv/ g sensitivity change due to temperature 3 v s = 3 v 0.015 %/c zero g bias level (ratiometric) each axis 0 g voltage at x out , y out v s = 3 v 1.35 1.5 1.65 v 0 g offset vs. temperature 0.6 m g /c noise performance noise density x out , y out 280 g /hz rms frequency response 4 bandwidth x out , y out t 5 no external filter 1600 hz 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 actuation current +60 a output change at x out self test 0 to self test 1 ?150 mv output change at y out self test 0 to self test 1 +150 mv output amplifier output swing low no load 0.1 v output swing high no load 2.8 v power supply operating voltage range 1.8 5.25 v supply current v s = 3 v 320 a turn-on time 7 no external filter 1 ms temperature operating temperature range ?25 +70 c 1 defined as coupling between 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 ). 5 bandwidth with external capacitors = 1/(2 32 k c). for c x , c y = 0.003 f, bandwidth = 1.6 khz. for c x , c y = 10 f, bandwidth = 0.5 hz. 6 self-test response changes cubically with v s . 7 turn-on time is dependent on c x , c y and is approximately 160 c x or c y + 1 ms, where c x , c y are in f.
adxl323 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 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. t p t l t 25c to peak t s preheat c r itic a lzone t l to t p temperature time ramp-down ramp-up t smin t smax t p t l 06237-002 figure 2. recommended soldering profile table 3. 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 maximum temperature (t smax ) 150c 200c time (t smin to t smax ), t s 60 sec to 120 s 60 sec to 180 sec t smax to t l ramp-up rate 3c/sec max 3c/sec max 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 max 6c/sec max time 25c to peak temperatur e 6 minutes max 8 minutes max esd caution esd (electrostatic discharge) sensitive device. electrosta tic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge with out 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.
adxl323 rev. 0 | page 5 of 16 pin configuration and fu nction descriptions nc = no connect nc 1 st 2 com 3 nc 4 x out 12 nc 11 y out 10 nc 9 com com com nc 5678 16 nc 15 v s 14 v s 13 nc adxl323 top view (not to scale) +x +y 06237-003 figure 3. pin configuration c enter pad is not internally connected but should be soldered for mechanical integrity 0.50 max 0.65 0.325 1.95 0.65 0.325 4 4 0.35 max 1.95 dimensions shown in millimeters 06237-004 figure 4. recommended pcb layout table 4. pin function descriptions pin no. mnemonic description 1 nc no connect 2 st self test 3 com common 4 nc no connect 5 com common 6 com common 7 com common 8 nc no connect 9 nc no connect 10 y out y channel output 11 nc no connect 12 x out x channel output 13 nc no connect 14 v s supply voltage (1.8 v to 5.25 v) 15 v s supply voltage (1.8 v to 5.25 v) 16 nc no connect
adxl323 rev. 0 | page 6 of 16 typical performance characteristics n > 1000 for all typical performance plots, unless otherwise noted. 16 14 0 2 4 6 8 10 12 0.95 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 % of population output (v) 06237-005 figure 5. x-axis zero g bias at 25c, v s = 2 v 40 35 0 5 10 15 20 25 30 1.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58 % of population output (v) 06237-006 figure 6. x-axis zero g bias at 25c, v s = 3 v 30 0 2.30 2.34 2.38 2.42 2.50 2.58 2.46 2.54 2.62 2.66 2.70 % of population output (v) 25 20 15 10 5 06237-007 figure 7. x-axis zero g bias at 25c, v s = 5 v 16 14 0 2 4 6 8 10 12 0.95 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 % of population output (v) 06237-008 figure 8. y-axis zero g bias at 25c, v s = 2 v 35 0 5 10 15 20 25 30 1.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58 % of population output (v) 06237-009 figure 9. y-axis zero g bias at 25c, v s = 3 v 30 0 2.30 2.34 2.38 2.42 2.50 2.58 2.46 2.54 2.62 2.66 2.70 % of population output (v) 25 20 15 10 5 06237-010 figure 10. y-axis zero g bias at 25c, v s = 5 v
adxl323 rev. 0 | page 7 of 16 35 0 5 10 15 25 30 20 ?2.5 2.52.01.5 1.0 0.5 0 ?0.5?1.0?1.5?2.0 % of population temperature coefficient (m g /c) 06237-011 figure 11. x-axis zero g bias temperature coefficient, v s = 3 v 35 0 ?2.5 ?2.0 ?1.5 ?1.0 0 1.0 ?0.5 0.5 1.5 2.0 2.5 % of population temperature coefficient (m g /c) 30 25 20 15 10 5 06237-012 figure 12. x-axis zero g bias temperature coefficient, v s = 5 v 1.55 1.54 1.53 1.52 1.51 1.50 1.49 1.48 1.47 1.46 1.45 ?30 ?20 ?10 0 10 20 30 40 50 60 70 80 volts temperature (c) n=8 06237-013 figure 13. x-axis zero g bias vs. temperature; eight parts soldered to pcb, v s = 3 v 40 35 0 5 10 15 25 30 20 ?2.5 2.52.01.5 1.0 0.5 0 ?0.5?1.0?1.5?2.0 % of population temperature coefficient (m g /c) 06237-014 figure 14. y-axis zero g bias temperature coefficient, v s = 3 v 40 0 ?2.5 ?2.0 ?1.5 ?1.0 0 1.0 ?0.5 0.5 1.5 2.0 2.5 % of population temperature coefficient (m g /c) 35 30 25 20 15 10 5 06237-015 figure 15. y-axis zero g bias temperature coefficient, v s = 5 v 1.55 1.54 1.53 1.52 1.51 1.50 1.49 1.48 1.47 1.46 1.45 ?30 ?20 ?10 0 10 20 30 40 50 60 70 80 volts temperature (c) n=8 06237-016 figure 16. y-axis zero g bias vs. temperature; eight parts soldered to pcb, v s = 3 v
adxl323 rev. 0 | page 8 of 16 35 30 0 5 10 15 20 25 0.170 0.174 0.178 0.182 0.186 0.190 0.194 0.198 0.202 0.206 0.210 % of population sensitivity (v/ g ) 06237-017 figure 17. x-axis sensitivity at 25c, v s = 2 v 60 0 10 20 30 40 50 0.26 0.34 0.33 0.32 0.31 0.30 0.29 0.28 0.27 % of population sensitivity (v/ g ) 06237-018 figure 18. x-axis sensitivity at 25c, v s = 3 v 25 0 0.50 0.51 0.52 0.53 0.55 0.57 0.54 0.56 0.58 0.59 0.60 % of population sensitivity (v/ g ) 20 15 10 5 06237-019 figure 19. x-axis sensitivity at 25c, v s = 5 v 40 35 30 0 5 10 15 20 25 0.170 0.174 0.178 0.182 0.186 0.190 0.194 0.198 0.202 0.206 0.210 % of population sensitivity (v/ g ) 06237-020 figure 20. y-axis sensitivity at 25c, v s = 2 v 70 60 0 10 20 30 40 50 0.26 0.34 0.33 0.32 0.31 0.30 0.29 0.28 0.27 % of population sensitivity (v/ g ) 06237-021 figure 21. y-axis sensitivity at 25c, v s = 3 v 40 0 0.50 0.51 0.52 0.53 0.55 0.57 0.54 0.56 0.58 0.59 0.60 % of population sensitivity (v/ g ) 35 30 25 20 15 10 5 06237-022 figure 22. y-axis sensitivity at 25c, v s = 5 v
adxl323 rev. 0 | page 9 of 16 90 80 70 60 0 10 20 30 40 50 ?2.0 ?1.6 ?1.2 ?0.8 ?0.4 0 0.4 0.8 1.2 1.6 2.0 % of population drift (%) 06237-023 figure 23. x-axis sensitivity drift over temperature, v s = 3 v 100 0 ?2.0 ?1.6 ?1.2 ?0.8 ?0.4 0 0.4 0.8 1.2 1.6 2.0 % of population drift (%) 90 80 70 60 50 40 30 20 10 06237-024 figure 24. x-axis sensitivity drift over temperature, v s = 5 v 0.33 0.32 0.31 0.30 0.29 0.28 0.27 ?30 8070605040302010 0 ?10?20 sensitivity (v/ g ) temperature (c) n=8 06237-025 figure 25. x-axis sensitivity vs. temperature eight parts soldered to pcb, v s = 3 v 70 60 0 10 20 30 40 50 ?2.0 ?1.6 ?1.2 ?0.8 ?0.4 0 0.4 0.8 1.2 1.6 2.0 % of population drift (%) 06237-026 figure 26. y-axis sensitivity drift over temperature, v s = 3 v 80 0 ?2.0 ?1.6 ?1.2 ?0.8 ?0.4 0 0.4 0.8 1.2 1.6 2.0 % of population drift (%) 70 60 50 40 30 20 10 06237-027 figure 27. y-axis sensitivity drift over temperature, v s = 5 v 0.33 0.32 0.31 0.30 0.29 0.28 0.27 ?30 8070605040302010 0 ?10?20 sensitivity (v/ g ) temperature (c) n=8 06237-028 figure 28. y-axis sensitivity vs. temperature eight parts soldered to pcb, v s = 3 v
adxl323 rev. 0 | page 10 of 16 600 500 400 300 200 100 0 06 5 4 3 2 1 current (a) supply (v) 06237-029 figure 29. typical current co nsumption vs. supply voltage ch1 1.00v b w ch2 500mv b w ch3 500mv ch4 500mv m1.00ms a ch1 300mv 4 3 2 1 t 9.400% t 06237-030 figure 30. typical turn-on time; c x , c y = 0.0047 f, v s = 3 v
adxl323 rev. 0 | page 11 of 16 theory of operation the adxl323 is a complete 2-axis acceleration measurement system on a single, monolithic ic. the adxl323 has a measure- ment 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 accelera- tion 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 meas- ured 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 band- width of the device by adding a capacitor. this filtering improves measurement resolution and helps prevent aliasing. mechanical sensor the adxl323 uses a single structure for sensing the x-axis and y-axis. as a result, the sense directions of the two axes 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, of course, be calibrated out at the system level. performance rather than using additional temperature compensation circuitry, innovative design techniques ensure that high performance is built in to the adxl323. 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 +70c temperature range). figure 13 and figure 16 show the zero g output performance of eight parts (x-axis and y-axis) soldered to a pcb over a ?25c to +70c temperature range. figure 25 and figure 28 demonstrate the typical sensitivity shift over temperature for supply voltages of 3 v. this is typically better than 1% over the ?25c to +70c temperature range.
adxl323 rev. 0 | page 12 of 16 applications power supply decoupling for most applications, a single 0.1 f capacitor, c dc , placed close to the adxl323 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 adxl323 ground to the power supply ground is low impedance because noise transmitted through ground has an effect similar to that of noise transmitted through v s . setting the bandwidth using c x , c y , and c z the adxl323 has provisions for band limiting the x out pin and the y out pin. 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 5. 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 ?500 m g (corresponding to ?150 mv) in the x-axis, and 500 m g (or 150 mv) on the y-axis. this st pin can be left open circuit or connected to common (com) 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 example, if there are multiple supply voltages), 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 and y out . the output of the adxl323 has a typical bandwidth of greater than 1600 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 further decreased to reduce noise and improve resolution. the adxl323 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 applica- tion to maximize the resolution and dynamic range of the accelerometer. with the single-pole, roll-off characteristic, the typical noise of the adxl323 is determined by )1.6( = bw density noise noiserms 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 use with operating voltages other than 3 v the adxl323 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 5.25 v. note that some performance parameters change as the supply voltage is varied.
adxl323 rev. 0 | page 13 of 16 the adxl323 output is ratiometric; therefore, the output sensitivity (or scale factor) varies proportionally to the supply voltage. at v s = 5 v, the output sensitivity is typically 550 mv/ g . at v s = 2 v, the output sensitivity is typically 190 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 180 g /hz, while at v s = 1.8 v, the noise density is typically 360 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 adxl323 is approximately ?700 mv for the x-axis and +700 mv for the y-axis. at v s = 1.8 v, the self-test response is approximately ?40 mv for the x-axis and +40 mv for the y-axis. the supply current decreases as the supply voltage decreases. typical current consumption at v s = 5 v is 500 a, and typical current consumption at v s = 1.8 v is 180 a. axes of acceleration sensitivity a y a x t o p 06237-031 figure 31. axes of acceleration sensitivity, corresponding output voltage increases when accelerated along the sensitive axis x out = ? 1 g y out =0 g gravity x out =0 g y out =1 g x out =0 g y out =?1 g x out =1 g y out =0 g x out =0 g y out =0 g x out =0 g y out =0 g top top top top t o p 06237-032 figure 32. output response vs. orientation to gravity
adxl323 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 33. 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 temper ature range package description package option adxl323kcpz 1 3 g 3 v ?25c to +70c 16-lead lfcsp_lq cp-16-5a adxl323kcpzCrl 1 3 g 3 v ?25c to +70c 16-lead lfcsp_lq cp-16-5a eval-adxl323z 1 evaluation board 1 z = pb-free part.
adxl323 rev. 0 | page 15 of 16 notes
adxl323 rev. 0 | page 16 of 16 notes ?2007 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. d06237-0-6/07(0)

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