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high stability, low noise vibration rejecting yaw rate gyro scope data sheet adxrs646 rev. 0 information furnished by analog devices is b elieved 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. n o 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 ? 2011 analog devices, inc. all rights reserved. f eatures 12/ hr bias stability z - axis (yaw rate) response 0.01/sec angle random walk high vibration rejection over wide frequency measurement range extendable to a maximum of 450/s ec 10, 000 g powered shock survivability ratiometric to referenced supply 6 v single - supply operation ? 40c to + 10 5c operation self - test on digital command ultrasmall and light (<0.15 cc, <0.5 gram) temperature sensor output complete rate gyroscope on a si ngle chip rohs compliant a pplications industrial a pplications severe mechanical environments platform stabilization g eneral description the adxrs646 is a high performance angular rate sensor (gyroscope) that offers excellent vibration immunity . b ias stability is a widely - recognized figure of merit for high performance gyroscope s, but in real - world applications, vibration sensitivity is often a more significant performance limitation and should be consider ed in gyroscope selection . the adxrs646 offers superior vibration immunity and acceleration rejection as well as a low bias drift of 12 /hr (typ ical ), enabling it to offer rate sensing in harsh environments where shock and vibration are present. the adxrs646 is manufactured using the analog devices, inc ., patented high volume b i mos surface - micromachining process . an advanced, differential, quad sensor de sign provides the improved acceleration and vibration rejection. the output signal, rateout , is a voltage proportional to angular rate about the axis normal to the top surface of the package. the measurement range is a minimum of 250/sec. the output is ratiometric with respect to a provided reference supply. other external capacitors are required for operation. a temperature output is provided for compensation techniques. two digital self - test inputs electromechanic ally excite the sensor to test proper operation of both the sensor and the signal cond i - tioning circuits. the adxrs646 is available in a 7 mm 7 mm 3 mm c bga chip - scale package. f unctional block diag ram figure 1 . v dd agnd pgnd av cc st2 st1 temp v ratio r out cp1 cp2 cp3 cp4 cp5 sumj rateout demod 180k? 1% 22nf 100nf 22nf 100nf 100nf 100nf drive amp mechanical sensor charge pump and voltage regulator c out 6v 6v 3v to 6v (adc ref) ac amp vga 25k? @ 25c adxrs646 25k? self-test 09771-001
adxrs646 data sheet rev. 0 | page 2 of 12 table of contents features .............................................................................................. 1 applications ....................................................................................... 1 general description ......................................................................... 1 functional block diagram .............................................................. 1 revision history ............................................................................... 2 specifications ..................................................................................... 3 absolute maxim um ratings ............................................................ 4 rate sensitive axis ....................................................................... 4 esd caution .................................................................................. 4 pin configuration and function descriptions ............................. 5 typical performance characteristics ............................................. 6 theo ry of operation .........................................................................9 setting bandwidth .........................................................................9 temperature output and calibration .........................................9 supply ratiometricity ................................................................ 10 null adjustment ......................................................................... 10 self - test function ...................................................................... 10 continuous self - te st .................................................................. 10 modifyin g the measurement range ........................................ 10 immunity to vibration .............................................................. 11 outline dimensions ....................................................................... 12 ordering guide .......................................................................... 12 revision h istory 9/ 11 revision 0: initial version
data sheet adxrs646 rev. 0 | page 3 of 12 specifications all minimum and maximum specifications are guaranteed. typical specifications are not guaranteed. t a = 2 5c, v s = av cc = v dd = 6 v, v ratio = av cc , angular rate = 0/sec, bandwidth = 80 hz (c out = 0.01 f), i out = 100 a, 1 g , unless otherwise noted. table 1. parameter test conditions /comments min typ max unit sensitivity 1 clockwise rotation is positive output measurement range 2 full - scale range over specifications range 250 300 /sec initial 8.5 9 9.5 mv//sec temperature drift 3 3 % nonlinearity best fit straight line 0.01 % of fs null 1 null ?40c to +105c 2.7 3.0 3.3 v calibrated null 4 ?40c to +105c 0.1 /sec temperature drift 3 3 /sec linear acceleration effect any axis 0.015 /sec/ g vibration rectification 25 g rms , 50 hz to 5 khz 0.0001 /s ec/ g 2 noise performance rate noise density t a 25 c 0.01 /sec/ hz rate noise density t a 105 c 0.015 /sec/ hz resolution floor t a = 25 c, 1 minute to 1 hour in - run 12 /hr frequency response bandwidth 5 3 db user adjustable up to specification 1000 hz sensor resonant frequency 15.5 17.5 20 khz self - test 1 st1 rateout response st1 pin from logic 0 to logic 1 ? 50 /sec st2 rateout response st2 pin from logic 0 to logic 1 50 /sec st1 to st2 mismatch 6 ? 5 0.5 + 5 % logic 1 input voltage st1 pin or st2 pin 4 v logic 0 input voltage 2 v input impedance st1 pin or st2 pin t o common 40 50 100 k? temperature sensor 1 v out at 25c load = 10 m ? 2.8 2.9 3.0 v scale factor 4 25c, v ratio = 6 v 10 mv/ c loa d to v s 25 k ? load to common 25 k? turn - on time 4 power on to 0.5/s ec of final with cp5 = 100 nf 50 ms output drive capability current drive for rated specifications 200 a capacitive load drive 1000 pf power supply operating voltage (v s ) 5.75 6.00 6.25 v quiescent supply current 4 ma temperature range specified performance ?40 +105 c 1 parameter is linearly ratiometric with v ratio . 2 measurement range is the maximum range possible, including output swing range, initial offset, sensitivity, offset drift, and sensitivity drift at 5 v supplies. 3 from +25c to ?40c or +25c to +105c. 4 based on characterization. 5 adjus ted by external capacitor, c out . reducing bandwidth below 0.01 hz does not result in further noise improvement. 6 self - test mismatch is described as (st2 + st1)/((st2 ? st1)/2).
adxrs646 data sheet rev. 0 | page 4 of 12 absolute maximum ratings table 2. parameter rating acceleration (any axis, 0.5 ms) unpowered 10,000 g powered 10,000 g v dd , av cc ?0.3 v to +6.6 v v ratio av cc st1, st2 av cc output short-circuit duration (any pin to common) indefinite operating temperature range ?55c to +125c storage temperature range ?65c to +150c stresses above those listed under the 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. drops onto hard surfaces can cause shocks of greater than 10,000 g and can exceed the absolute maximum rating of the device. care should be exercised in handling to avoid damage. rate sensitive axis this is a z-axis rate-sensing device (also called a yaw rate- sensing device). it produces a positive going output voltage for clockwise rotation about the axis normal to the package top, that is, clockwise when looking down at the package lid. figure 2. rateout signal incr eases with clockwise rotation esd caution rate axis longitudinal axis lateral axis + abcd g 1 7 ef a1 rate out rate in 4.75v 0.25v av cc = 5v v ratio /2 gnd 09771-002
data sheet adxrs646 rev. 0 | page 5 of 12 pin configuration an d function descripti ons figure 3 . pin configuration table 3 . pin function descriptions pin no. mnemonic description 6d, 7d cp5 hv filter capacito r, 100 n f (5%) . 6a, 7b cp4 charge pump capacitor, 22 nf (5%) . 6c, 7c cp3 charge pump capacitor, 22 nf (5%) . 5a, 5b cp1 charge pump capacitor, 22 nf (5%) . 4a, 4b cp2 charge pump capacitor, 22 nf (5%) . 3a, 3b av cc positive analog supply. 1b, 2a rateout rate signal output. 1c, 2c sumj output amp summing junction. 1d, 2d d nc do not connect to this pin . 1e, 2e v ratio reference supply for ratiometric output. 1f, 2g agnd analog supply return. 3f, 3g temp temperature voltage output. 4f, 4g st2 self - test for sensor 2. 5f, 5g st1 self - test for sensor 1. 6g, 7f pgnd charge pump supply return. 6e, 7e v dd positive charge pump supply. 09771-003 pgnd st1 st2 temp agnd v ratio dnc sumj rateout av cc cp2 cp1 cp4 cp3 cp5 v dd g f e d c b a 7 6 5 4 3 2 1 notes 1. dnc = do not connect to this pin. bottom view
adxrs646 data sheet rev. 0 | page 6 of 12 typical performance characteristics n > 1000 for all typical performance plots, unless otherwise noted. figure 4 . null bias at 25c figure 5 . null drift over temperature (v ratio = 5 v) figure 6 . n ull output over temperature, 16 parts in sockets (v ratio = 5 v) figure 7 . sensitivity at 25c figure 8 . sensitivity drift over temperature figure 9 . typical root allan deviation at 25c vs. averaging time 30 0 5 10 15 20 25 percent of population (%) rateout (v) 2.75 2.80 2.85 2.90 2.95 3.00 3.05 3.10 3.15 3.20 3.25 09771-004 30 0 5 10 15 20 25 percent of population (%) drift (/sec/c) ?0.30 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 0.05 0.10 0.15 0.20 0.25 0.30 09771-005 3.5 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 null (v) temperature (c) ?60 ?40 ?20 0 20 40 60 80 100 120 140 09771-100 35 30 25 20 15 10 5 0 percent of population (%) sensitivity (mv//sec) 8.5 8.6 8.7 8.8 8.9 9.0 9.1 9.2 9.3 9.4 9.5 09771-010 40 35 30 25 20 15 10 5 0 percent of population (%) percent drift (%) ?10 ?8 ?6 ?4 ?2 0 2 4 6 8 10 12 14 16 18 20 09771-0 1 1 1k 100 10 root allan devi a tion (/hour rms) a veraging time (seconds) 0.01 0.1 1 10 100 1k 100k 10k 09771-012
data sheet adxrs646 rev. 0 | page 7 of 12 figure 10 . st1 output change at 25c (v ratio = 5 v) figure 1 1 . st1 output change vs. temperature, 16 parts in sockets figure 12 . self - test mismatch at 25c (v ratio = 5 v) figure 13 . st2 output change at 25c (v ratio = 5 v) figure 14 . st2 output change vs. temperature, 16 parts in sockets figure 15 . adxrs646 frequency response with a 2.2 khz output filter 25 0 5 10 15 20 percent of population (%) st1 (mv) ?650 ?630 ?610 ?590 ?570 ?550 ?530 ?510 ?490 ?470 ?450 ?430 ?410 ?390 ?370 ?350 09771-006 ?0.30 ?0.35 ?0.40 ?0.45 ?0.50 ?0.55 ?0.60 ?0.65 ?0.70 ?0.75 st1 (v) temperature (c) ?60 ?40 ?20 0 20 40 60 80 100 120 140 09771-104 70 60 50 40 30 20 10 0 percent of population (%) mismatch (%) ?4 ?3 ?2 ?1 0 1 2 3 4 09771-008 25 0 5 10 15 20 percent of population (%) st2 (mv) 350 370 390 410 430 450 470 490 510 530 550 570 590 610 630 650 09771-007 0.75 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 st2 (v) temperature (c) ?60 ?40 ?20 0 20 40 60 80 100 120 140 09771-103 9 ?18 ?15 ?12 ?9 ?6 ?3 0 3 6 0 ?90 ?80 ?70 ?60 ?50 ?40 ?30 ?20 ?10 magnitude response (db) phase response (degrees) frequency (khz) 0.1 1 10 09771-101 c out = 470pf magnitude phase
adxrs646 data sheet rev. 0 | page 8 of 12 figure 16 . v temp output at 25c (v ratio = 5 v) figure 17 . v temp output vs. temperature figure 18 . current consumption at 25c (v ratio = 5 v) 80 70 60 50 40 30 20 10 0 percent of population (%) v temp output (v) 2.70 2.75 2.80 2.85 2.90 2.95 3.00 3.05 3.10 3.15 3.20 3.25 3.30 09771-009 4.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 v temp (v) temperature (c) ?100 ?50 0 50 100 150 09771-102 35 30 25 20 15 10 5 0 percent of population (%) current consumption (ma) 2.8 2.9 3.0 3.1 3.2 3.3 3.4 09771-013
data sheet adxrs646 rev. 0 | page 9 of 12 theory of operation the adxrs646 operates on the principle of a resonator gyro scope . figure 19 shows a simplified version of one of four polysilicon sensing structures. each sensing structure contains a dither frame that is electrostatically driven to resonance. this pro duces the necessary velocity element to produce a coriolis force when experiencing angular rate. the adxrs646 is designed to sense a z - axis (yaw) angular rate. when the sensing structure is exposed to angular rate, the resulting coriolis force couples into an outer sense frame, which contains movable fingers that are placed between fixed pickoff fingers. this forms a capacitive pickoff structure that senses coriolis motion. the resulting s ignal is fed to a series of gain and demodulation stages that produce the electrical rate signal output. the quad sensor design rejects linear and angular acceleration, including external g - forces , shock, and vibration. th e rejection is achieved by mechani cally coupling the four sensing structures such that external g - forces appear as common - mode signals that can be removed by the fully differential architecture implemented in the adxrs646 . figure 19 . simp lified gyro scope sensing structure one corner the elec trostatic resonator requires 21 v for operation. because only 6 v are typically available in most applications , a charge pump is included on chip. if an external 21 v supply is available, the two capacitors on cp1 to cp4 can be omitted, and this supply can be connected to cp5 (pin 6 d, pin 7d). cp5 should not be grounded when power is applied to the adxrs646 . no damage o ccurs, but under certain conditions, the charge pump may fail to start up after the ground is removed without first removing power from the adxrs646 . setting bandwidth the combination of an external capaci tor ( c out ) and the on - chip resistor ( r out ) create s a low - pass filter that limit s the bandwidth of the adxrs646 rate response. the ?3 db frequency set by r out and c out is f out = 1/(2 r out c out ) and can be well controlled because r out is trimmed during manufacturing to 180 k? 1%. any external resistor applied between the rateout pin (1b, 2a) and sumj pin (1c, 2c) results in r out = (180 k r ext )/(180 k + r ext ) a n additional external filter is oft en added (in either hardware or software) to attenuate high frequency noise arising from demodu lation spikes at the 18 khz resonant frequency of the gyros cope . an r c output filter consisting of a 3.3 k series resistor and 22 nf shunt capacitor (2.2 khz pole) is recommended. temperature output a nd calibration it is common practice to temperature - calibrate gyros copes to improve their overall accuracy. the adxrs646 has a temperature - dependent voltage output t hat provides input to such a calibration method. the temperature sensor structure is shown in figure 20 . the temperature output is characteristi- cally nonlinear, and any load resistance connected to the temp output results in decreasing the temp output and its temperature coefficient. therefore, buffering the output is recommended. the voltage a t temp (3f, 3g) is nominally 2.9 v at 25c, and v ratio = 6 v. t he temperature coefficient is 10 mv/c (typ ical ) at 25 c ; the output response over the full temperature range is shown in figure 17 . although the temp output is highly r epeatable, it has only modest absolute accuracy. figure 20 . temperature sensor structure x y z 09771-015 v ratio v temp r fixed r temp 09771-016
adxrs646 data sheet rev. 0 | page 10 of 12 supply ratiometricit y the null output voltage (rateout), sensitivity, self - test responses (st1 and st2), and temperature output ( temp ) of the adxrs646 are ratiometric to v ratio . therefore, using the adxrs646 with a supply - ratiometric adc results in self - cancellation of errors resulting from minor supply variations. there remains a small, usually negligible, error due to non - ratiometric behavior. note that , to guarantee full measurement range, v ratio should not be greater than av cc . null adjustment the nominal 3.0 v null output voltage is tru e for a symmetrical swing range at rateout (1b, 2a). however, a n asymmetric output swing may be suitable in some applications. null adjust - ment is possible by injecting a suitable current to sumj (1c, 2c). note that supply disturbances may cause some null instability. digital supply noise should be avoided, particularly in this case. self - test function the adxrs646 includes a self - test feature that actuates each of the sensing structures and associated electro nics in the same manner as if the gyroscope were subjected to angular rate. self - test is activated by applying the standard l ogic h igh level st1 pin (5f, 5g), the st2 pin (4f, 4g), or both. applying a logic high to pin st1 causes the voltage at rateout to change by ? 450 m v (typ ical ) , and applying a logic high to pin st2 causes an opposite change of +450 m v (typ ical ) . the voltage applied to the st1 and st2 pins must never be greater than av cc . the self - test response follows the temperature dependence of the viscosity of the package atmosphere, approximately 0.25%/c. activating both st1 and st2 simultaneously is not damaging. the output responses generated by st1 and st2 are closely matched ( 2 %), but actuating both simultaneously may result in a small appare nt null bias shift proportional to the degree of self - test mismatch. continuous self - test the on - chip integration of the adxrs646 , as well as the mature process with which it is manufactured, have provided the gyroscope with field - proven reliability. as an additional failure detection measure, self - test can be performed at power - up or occasionally during operation . however, some applications may require continuous self - test while sensing rotation rate. detai ls outlining continuous self - test techniques are available in the an - 768 application note , using the adxrs150/adxrs300 in continuous self - test mode . although the title of this application note refers to other a nalog d evices gyroscopes, the techniques apply equally to the adxrs646 . modifying the m easurement r ange the adxrs646 scale factor can be reduced to extend the mea surement range to as much as 450/s ec by adding a single 225 k? resistor between rateout and sumj. if an external resistor is added between rateout and sumj , c out must be proportionally increased to maintain correct bandwidth.
data sheet adxrs646 rev. 0 | page 11 of 12 immunity to vibration gyr oscopes are design ed to respond only to rotation . however, all gyroscopes respond to linear motion as well, to varying degrees. while bias stability is often used as the primary figure of merit for evaluating high performance gyroscopes, many additional er ror sources are present in real - world applications. especially in applications that require motion sensors, vibration and acceleration are present , and the resulting errors often overwhelm bias drift. its differential, quad - sensor design makes the adxrs646 inherently resistant to vibration, without the need for compensation. the excellent vibration immunity of the adxrs646 is demonstrated in figure 21 and figure 22. figure 21 shows the adxrs646 output response with and without random 15 g rms vibration applied at 2 0 hz to 2 khz. performance is similar regardless of the direction of input vibration. figure 21 . adxrs646 output response with and without random vibration (15 g rms, 2 0 hz to 2 khz) ; gyro scope bandwidth set to 1600 hz to further improve immunity to vibration and acceleratio n, some g - sensitivity compensation can be performed using an accelerometer. this technique is most successful when the response to vibration is constant regardless of vibration frequency . figure 22 demonstrates the adxrs646 dc bias response to a 5 g sinusoidal vibration over the 20 hz to 5 khz range. this figure shows that there are no sensitive frequencies present and that vibration rectification is vanishingly small. accordingly, g - sensitivity compensation using an accelerometer is possible where needed, but the inherent device performance is sufficient for many applications. figure 22 . adxrs646 sine vibration output response ( 5 g , 20 hz to 5 khz ) ; gyro scope bandwidth set to 1600 hz 1 0.1 0.01 0.001 0.0001 0.00001 (/sec) 2 / hz frequency (hz) 10 100 1k 10k 09771-017 with vibration no vibration 0.12 ?0.04 ?0.02 0 0.02 0.04 0.06 0.08 0.10 (/sec) frequency (hz) 10 100 1k 10k 09771-018
adxrs646 data sheet rev. 0 | page 12 of 12 outline dimensions figure 23. 32-lead ceramic ball grid array [cbga] (bg-32-3) dimensions shown in millimeters ordering guide model 1 temperature range package description package option adxrs646bbgz C40c to +105c 32-lead ceramic ball grid array [cbga] bg-32-3 adxrs646bbgz-rl C40c to +105c 32-lead ceramic ball grid array [cbga] bg-32-3 EVAL-ADXRS646Z evaluation board 1 z = rohs compliant part. a b c d e f g 76543 top view detail a ball diameter 0.60 0.55 0.50 0.60 max 0.25 min coplanarity 0.15 21 * a1 corner index area 3.20 max 2.50 min * ball a1 identifier is gold plated and connected to the d/a pad internally via holes. 10-26-2009-b 7.05 6.85 sq 6.70 a1 ball corner bottom view detail a 0.80 bsc 4.80 bsc sq seating plane 3 .80 max ?2011 analog devices, inc. all ri ghts reserved. trademarks and registered trademarks are the property of their respective owners. d09771-0-9/11(0)

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