ADXRS623

±150°/Sec Yaw Rate Gyroscope ADXRS623 FEATURES Complete rate gyroscope on a single chip Z-axis (yaw rate) response High vibration rejection over wide frequency 2000 g powered shock survivability Ratiometric to referenced supply 5 V single-supply operation –40°C to +105°C operation Self-test on digital command Ultrasmall and light ( 1000 for all typical performance plots, unless otherwise noted. 25 30 PERCENT OF POPULATION (%) 20 PERCENT OF POPULATION (%) 25 20 15 15 10 10 5 5 08890-004 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 −10 −8 −6 −4 −2 0 2 4 6 8 10 RATEOUT (V) PERCENT DRIFT (%) Figure 4. Null Output at 25°C (VRATIO = 5 V) Figure 7. Sensitivity Drift over Temperature 45 40 45 40 PERCENT OF POPULATION (%) PERCENT OF POPULATION (%) 35 30 25 20 15 10 5 08890-005 35 30 25 20 15 10 5 08890-008 08890-009 –500 –600 –700 –800 –900 –1000 –1100 –1200 –1300 –0.4 –0.3 –0.2 –0.1 0 (°/s/°C) 0.1 0.2 0.3 0.4 0.5 ST1 Δ (mV) Figure 5. Null Drift over Temperature (VRATIO = 5 V) Figure 8. ST1 Output Change at 25°C (VRATIO = 5 V) 35 30 45 40 PERCENT OF POPULATION (%) PERCENT OF POPULATION (%) 35 30 25 20 15 10 5 0 25 20 15 10 5 0 500 600 700 800 900 1000 1100 1200 1300 11.00 11.25 11.50 11.75 12.00 12.25 12.50 12.75 13.00 13.25 13.50 13.75 14.00 08890-006 SENSITIVITY (mV/°/s) ST2 Δ (mV) Figure 6. Sensitivity at 25°C (VRATIO = 5 V) Rev. 0 | Page 6 of 12 Figure 9. ST2 Output Change at 25°C (VRATIO = 5 V) 1400 –1400 0 –0.5 0 08890-007 0 0 ADXRS623 30 40 35 PERCENT OF POPULATION (%) PERCENT OF POPULATION (%) 08890-010 25 30 25 20 15 10 5 0 2.40 2.42 2.44 2.46 2.48 2.50 2.52 2.54 2.56 2.58 2.60 VOLTAGE (V) 20 15 10 5 125 135 145 155 165 175 185 195 MEASUREMENT RANGE (°/s) Figure 10. Measurement Range Figure 13. VTEMP Output at 25°C (VRATIO = 5 V) 3.3 3.1 1.5 1.0 ST2 0.5 2.9 2.7 VOLTAGE (V) VOLTAGE (V) 2.5 2.3 2.1 0 −0.5 ST1 −1.0 1.9 1.7 256 PARTS 08890-014 −20 08890-011 −1.5 −40 0 20 40 60 80 100 120 1.5 –40 –20 0 20 40 60 80 100 120 TEMPERATURE (°C) TEMPERATURE (°C) Figure 11. Typical Self-Test Change over Temperature 30 Figure 14. VTEMP Output over Temperature (VRATIO = 5 V) 60 50 40 REF Y X +45° –45° PERCENT OF POPULATION (%) 25 20 30 15 (g OR °/s) 20 10 0 10 5 –10 0 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 CURRENT CONSUMPTION (mA) 08890-012 770 790 TIME (ms) 810 830 850 Figure 12. Current Consumption at 25°C (VRATIO = 5 V) Figure 15. g and g × g Sensitivity for a 50 g, 10 ms Pulse Rev. 0 | Page 7 of 12 08890-015 –20 750 08890-013 0 ADXRS623 2.0 1.8 1.6 PEAK RATEOUT (°/s) 1.4 1.2 (°/s) 08890-016 0.10 LATITUDE LONGITUDE RATE 0.05 1.0 0.8 0.6 0 –0.05 0.4 0.2 0 20 40 60 80 100 120 140 08890-019 0 100 –0.10 TIME (Hours) 1k FREQUENCY (Hz) 10k Figure 16. Typical Response to 10 g Sinusoidal Vibration (Sensor Bandwidth = 2 kHz) Figure 19. Typical Shift in 90 Sec Null Averages Accumulated over 140 Hours 400 300 DUT1 OFFSET BY +200°/s 200 100 (°/s) 0.10 0.05 (°/s) 0 –100 –200 –300 –400 0 50 100 (ms) 150 200 250 DUT2 OFFSET BY –200°/s 0 –0.05 08890-017 0 600 1200 1800 TIME (Seconds) 2400 3000 3600 Figure 17. Typical High g (2500 g) Shock Response (Sensor Bandwidth = 40 Hz) 1 Figure 20. Typical Shift in Short-Term Null (Bandwidth = 1 Hz) 0.1 0.1 0.01 (°/s/ Hz rms) (°/s rms) 0.01 0.001 08890-018 0.1 1 10 100 1k 10k 100k 100 1k FREQUENCY (Hz) 10k 100k AVERAGE TIME (Seconds) Figure 18. Typical Root Allan Deviation at 25°C vs. Averaging Time Figure 21. Typical Noise Spectral Density (Bandwidth = 40 Hz) Rev. 0 | Page 8 of 12 08890-021 0.001 0.01 0.0001 10 08890-020 –0.10 ADXRS623 THEORY OF OPERATION The ADXRS623 operates on the principle of a resonator gyroscope. Two polysilicon sensing structures each contain a dither frame that is electrostatically driven to resonance, producing the necessary velocity element to produce a Coriolis force while rotating. At two of the outer extremes of each frame, orthogonal to the dither motion, are movable fingers that are placed between fixed pickoff fingers to form a capacitive pickoff structure that senses Coriolis motion. The resulting signal is fed to a series of gain and demodulation stages that produce the electrical rate signal output. The dual-sensor design rejects external g forces and vibration. Fabricating the sensor with signal conditioning electronics preserves signal integrity in noisy environments. The electrostatic resonator requires 18 V to 20 V for operation. Because only 5 V are typically available in most applications, a charge pump is included on chip. If an external 18 V to 20 V supply is available, the two capacitors on CP1 through CP4 can be omitted, and this supply can be connected to the CP5 pin (6D, 7D). Note that CP5 should not be grounded when power is applied to the ADXRS623. Although no damage occurs, under certain conditions, the charge pump may fail to start up after the ground is removed without first removing power from the ADXRS623. Figure 22 shows the effect of adding a 250 Hz filter to the output of an ADXRS623 set to 40 Hz bandwidth (as shown in Figure 21). High frequency demodulation artifacts are attenuated by approximately 18 dB. 0.1 0.01 (°/s/ Hz rms) 0.001 0.0001 0.00001 100 1k FREQUENCY (Hz) 10k 100k Figure 22. Noise Spectral Density with Additional 250 Hz Filter TEMPERATURE OUTPUT AND CALIBRATION It is common practice to temperature-calibrate gyroscopes to improve their overall accuracy. The ADXRS623 has a temperature proportional voltage output that provides input to such a calibration method. The temperature sensor structure is shown in Figure 23. The temperature output is characteristically nonlinear, and any load resistance connected to the TEMP output results in decreasing the TEMP output and temperature coefficient. Therefore, buffering the output is recommended. The voltage at the TEMP pin (3F, 3G) is nominally 2.5 V at 25°C and VRATIO = 5 V. The temperature coefficient is ~9 mV/°C at 25°C. Although the TEMP output is highly repeatable, it has only modest absolute accuracy. VTEMP VRATIO 08890-023 SETTING BANDWIDTH External Capacitor COUT is used in combination with the on-chip ROUT resistor to create a low-pass filter to limit the bandwidth of the ADXRS623 rate response. The –3 dB frequency set by ROUT and COUT is f OUT = (2 × π × ROUT × COUT ) 1 and can be well controlled because ROUT is trimmed during manufacturing to be 180 kΩ ± 1%. Any external resistor applied between the RATEOUT pin (1B, 2A) and the SUMJ pin (1C, 2C) results in ROUT = (180 kΩ × REXT ) (180 kΩ + REXT ) RFIXED RTEMP Figure 23. ADXRS623 Temperature Sensor Structure In general, an additional hardware or software filter is added to attenuate high frequency noise arising from demodulation spikes at the gyroscope’s 14 kHz resonant frequency (the noise spikes at 14 kHz can be clearly seen in the power spectral density curve shown in Figure 21). Typically, the corner frequency of this additional filter is set to greater than 5× the required bandwidth to preserve good phase response. CALIBRATED PERFORMANCE Using a three-point calibration technique, it is possible to calibrate the null and sensitivity drift of the ADXRS623 to an overall accuracy of nearly 200°/hour. An overall accuracy of 40°/hour or better is possible using more points. Limiting the bandwidth of the device reduces the flat-band noise during the calibration process, improving the measurement accuracy at each calibration point. Rev. 0 | Page 9 of 12 08890-022 0.000001 10 ADXRS623 ADXRS623 AND SUPPLY RATIOMETRICITY The ADXRS623 RATEOUT and TEMP signals are ratiometric to the VRATIO voltage; that is, the null voltage, rate sensitivity, and temperature outputs are proportional to VRATIO. Thus, the ADXRS623 is most easily used with a supply-ratiometric ADC that results in self-cancellation of errors due to minor supply variations. There is some small error due to nonratiometric behavior. Typical ratiometricity error for null, sensitivity, selftest, and temperature output is outlined in Table 4. Note that VRATIO must never be greater than AVCC. Table 4. Ratiometricity Error for Various Parameters Parameter ST1 Mean Sigma ST2 Mean Sigma Null Mean Sigma Sensitivity Mean Sigma VTEMP Mean Sigma VS = VRATIO = 4.85 V 0.3% 0.21% −0.15% 0.22% −0.3% 0.2% 0.003% 0.06% −0.2% 0.05% VS = VRATIO = 5.15 V 0.09% 0.19% −0.2% 0.2% −0.05% 0.08% −0.25% 0.06% −0.04% 0.06% SELF-TEST FUNCTION The ADXRS623 includes a self-test feature that actuates each of the sensing structures and associated electronics as if subjected to angular rate. It is activated by standard logic high levels applied to Input ST1 (5F, 5G), Input ST2 (4F, 4G), or both. ST1 causes the voltage at RATEOUT to change about −1.0 V, and ST2 causes an opposite change of +1.0 V. The self-test response follows the viscosity temperature dependence of the package atmosphere, approximately 0.25%/°C. Activating both ST1 and ST2 simultaneously is not damaging. ST1 and ST2 are fairly closely matched (±5%), but actuating both simultaneously may result in a small apparent null bias shift proportional to the degree of self-test mismatch. ST1 and ST2 are activated by applying a voltage of greater than 0.8 × VRATIO to the ST1 and ST2 pins. ST1 and ST2 are deactivated by applying a voltage of less than 0.2 × VRATIO to the ST1 and ST2 pins. The voltage applied to ST1 and ST2 must never be greater than AVCC. CONTINUOUS SELF-TEST The one-chip integration of the ADXRS623 gives it higher reliability than is obtainable with any other high volume manufacturing method. In addition, it is manufactured under a mature BiMOS process with field-proven reliability. As an additional failure detection measure, a power-on self-test can be performed. However, some applications may warrant continuous self-test while sensing rate. Details about continuous self-test techniques are available in the AN-768 Application Note, Using the ADXRS150/ADXRS300 in Continuous Self-Test Mode, available at www.analog.com. NULL ADJUSTMENT The nominal 2.5 V null is for a symmetrical swing range at RATEOUT (1B, 2A). However, a nonsymmetrical output swing may be suitable in some applications. Null adjustment is possible by injecting a suitable current to SUMJ (1C, 2C). Note that supply disturbances may reflect some null instability. Digital supply noise should be avoided, particularly in this case. Rev. 0 | Page 10 of 12 ADXRS623 OUTLINE DIMENSIONS A1 BALL CORNER 7.05 6.85 SQ 6.70 *A1 CORNER INDEX AREA 7 6 5 4 3 2 1 A 4.80 BSC SQ 0.80 BSC B C D E F G TOP VIEW DETAIL A 3.80 MAX BOTTOM VIEW DETAIL A 0.60 MAX 0.25 MIN 3.20 MAX 2.50 MIN SEATING PLANE 0.60 0.55 0.50 COPLANARITY 0.15 BALL DIAMETER *BALL A1 IDENTIFIER IS GOLD PLATED AND CONNECTED TO THE D/A PAD INTERNALLY VIA HOLES. Figure 24. 32-Lead Ceramic Ball Grid Array [CBGA] (BG-32-3) Dimensions shown in millimeters ORDERING GUIDE Model1 ADXRS623WBBGZ ADXRS623WBBGZ-RL EVAL-ADXRS623Z 1 Temperature Range –40°C to +105°C –40°C to +105°C Package Description 32-Lead Ceramic Ball Grid Array (CBGA) 32-Lead Ceramic Ball Grid Array (CBGA) Evaluation Board 10-26-2009-B Package Option BG-32-3 BG-32-3 Z = RoHS Compliant Part. Rev. 0 | Page 11 of 12 ADXRS623 NOTES ©2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D08890-0-3/10(0) Rev. 0 | Page 12 of 12