High Stability, Low Noise Vibration Rejecting Yaw Rate Gyroscope ADXRS646 Data Sheet FEATURES GENERAL DESCRIPTION 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°/sec 10,000 g powered shock survivability Ratiometric to referenced supply 6 V single-supply operation −40°C to +105°C operation Self-test on digital command Ultrasmall and light (<0.15 cc, <0.5 gram) Temperature sensor output Complete rate gyroscope on a single chip RoHS compliant The ADXRS646 is a high performance angular rate sensor (gyroscope) that offers excellent vibration immunity. Bias stability is a widely-recognized figure of merit for high performance gyroscopes, but in real-world applications, vibration sensitivity is often a more significant performance limitation and should be considered in gyroscope selection. The ADXRS646 offers superior vibration immunity and acceleration rejection as well as a low bias drift of 12°/hr (typical), 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 BiMOS surface-micromachining process. An advanced, differential, quad sensor design 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. APPLICATIONS Industrial applications Severe mechanical environments Platform stabilization A temperature output is provided for compensation techniques. Two digital self-test inputs electromechanically excite the sensor to test proper operation of both the sensor and the signal conditioning circuits. The ADXRS646 is available in a 7 mm × 7 mm × 3 mm CBGA chip-scale package. FUNCTIONAL BLOCK DIAGRAM 3V TO 6V (ADC REF) 100nF 6V ST2 ST1 TEMP SELF-TEST 25kΩ @ 25°C AV CC 100nF VRATIO ADXRS646 25kΩ AGND DEMOD MECHANICAL SENSOR DRIVE AMP 6V AC AMP VGA ROUT VDD 180kΩ ±1% CHARGE PUMP AND VOLTAGE REGULATOR 100nF PGND SUMJ RATEOUT 100nF 22nF 22nF COUT 09771-001 CP1 CP2 CP3 CP4 CP5 Figure 1. Rev. B Document Feedback 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 ©2011–2014 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com ADXRS646 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Theory of Operation .........................................................................9 Applications ....................................................................................... 1 Setting Bandwidth .........................................................................9 General Description ......................................................................... 1 Temperature Output and Calibration .........................................9 Functional Block Diagram .............................................................. 1 Supply Ratiometricity ................................................................ 10 Revision History ............................................................................... 2 Null Adjustment ......................................................................... 10 Specifications..................................................................................... 3 Self-Test Function ...................................................................... 10 Absolute Maximum Ratings............................................................ 4 Continuous Self-Test .................................................................. 10 Rate Sensitive Axis ....................................................................... 4 Modifying the Measurement Range ........................................ 10 ESD Caution .................................................................................. 4 Immunity to Vibration .............................................................. 11 Pin Configuration and Function Descriptions ............................. 5 Outline Dimensions ....................................................................... 12 Typical Performance Characteristics ............................................. 6 Ordering Guide .......................................................................... 12 REVISION HISTORY 1/14—Rev. A to Rev. B Changes to Table 1 ............................................................................ 3 Changes to Figure Captions, Typical Performance Characteristics Section..................................................................... 6 Replaced Figure 8 ............................................................................. 6 Changes to Continuous Self-Test Section ................................... 10 9/12—Rev. 0 to Rev. A Changes to Figure 1 .......................................................................... 1 Changes to Figure 9 .......................................................................... 6 9/11—Revision 0: Initial Version Rev. B | Page 2 of 12 Data Sheet ADXRS646 SPECIFICATIONS All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed. TA = 25°C, VS = AVCC = VDD = 6 V, VRATIO = AVCC, angular rate = 0°/sec, bandwidth = 80 Hz (COUT = 0.01 µF), IOUT = 100 µA, ±1 g, unless otherwise noted. Table 1. Parameter SENSITIVITY 1 Measurement Range 2 Initial Temperature Drift 3 Nonlinearity NULL1 Null Temperature Drift3 Linear Acceleration Effect Vibration Rectification NOISE PERFORMANCE Rate Noise Density Rate Noise Density Resolution Floor FREQUENCY RESPONSE Bandwidth 4 Sensor Resonant Frequency SELF-TEST1 ST1 RATEOUT Response ST2 RATEOUT Response ST1 to ST2 Mismatch 5 Logic 1 Input Voltage Logic 0 Input Voltage Input Impedance TEMPERATURE SENSOR1 VOUT at 25°C Scale Factor 6 Load to VS Load to Common TURN-ON TIME6 OUTPUT DRIVE CAPABILITY Current Drive Capacitive Load Drive POWER SUPPLY Operating Voltage (VS) Quiescent Supply Current TEMPERATURE RANGE Specified Performance Test Conditions/Comments Clockwise rotation is positive output Full-scale range over specifications range Min Typ ±250 8.5 ±300 9 ±6.5 0.01 2.7 Any axis 25 g rms, 50 Hz to 5 kHz 3.0 ±3 0.015 0.0001 TA ≤ 25°C TA ≤ 105°C TA = 25°C, 1 minute to 1 hour in-run 0.01 0.015 12 Best fit straight line −40°C to +105°C ±3 dB user adjustable up to specification 15.5 ST1 pin from Logic 0 to Logic 1 ST2 pin from Logic 0 to Logic 1 1000 17.5 Max 9.5 3.3 20 +5 2 100 −5 4 ST1 pin or ST2 pin to common 40 50 Load = 10 MΩ 25°C, VRATIO = 6 V 2.8 2.9 10 25 25 °/sec mV/°/sec % % of FS V °/sec °/sec/g °/sec/g2 °/sec/√Hz °/sec/√Hz °/hr −50 50 ±0.5 ST1 pin or ST2 pin Unit °/sec °/sec % V V kΩ Power on to ±0.5°/sec of final with CP5 = 100 nF 50 V mV/°C kΩ kΩ ms For rated specifications 200 1000 µA pF 6.25 V mA +105 °C 5.75 −40 6.00 4 3.0 Hz kHz Parameter is linearly ratiometric with VRATIO. Measurement range is the maximum range possible, including output swing range, initial offset, sensitivity, offset drift, and sensitivity drift at 5 V supplies. From +25°C to −40°C or +25°C to +105°C. 4 Adjusted by external capacitor, COUT. Reducing bandwidth below 0.01 Hz does not result in further noise improvement. 5 Self-test mismatch is described as (ST2 + ST1)/((ST2 − ST1)/2). 6 Based on characterization. 1 2 3 Rev. B | Page 3 of 12 ADXRS646 Data Sheet ABSOLUTE MAXIMUM RATINGS RATE SENSITIVE AXIS Parameter Acceleration (Any Axis, 0.5 ms) Unpowered Powered VDD, AVCC VRATIO ST1, ST2 Output Short-Circuit Duration (Any Pin to Common) Operating Temperature Range Storage Temperature Range Rating 10,000 g 10,000 g −0.3 V to +6.6 V AVCC AVCC Indefinite −55°C to +125°C −65°C to +150°C This is a Z-axis rate-sensing device (also called a yaw ratesensing 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. RATE AXIS RATE OUT AVCC = 5V LONGITUDINAL AXIS 4.75V + VRATIO/2 7 RATE IN 1 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. A1 0.25V ABCDE FG LATERAL AXIS GND Figure 2. RATEOUT Signal Increases with Clockwise Rotation ESD CAUTION 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. Rev. B | Page 4 of 12 09771-002 Table 2. Data Sheet ADXRS646 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS BOTTOM VIEW VDD PGND CP5 CP3 CP4 7 6 ST1 CP1 5 ST2 CP2 4 AVCC 3 TEMP 2 1 G F VRATIO DNC SUMJ E D C RATEOUT B NOTES 1. DNC = DO NOT CONNECT TO THIS PIN. A 09771-003 AGND Figure 3. Pin Configuration Table 3. Pin Function Descriptions Pin No. 6D, 7D 6A, 7B 6C, 7C 5A, 5B 4A, 4B 3A, 3B 1B, 2A 1C, 2C 1D, 2D 1E, 2E 1F, 2G 3F, 3G 4F, 4G 5F, 5G 6G, 7F 6E, 7E Mnemonic CP5 CP4 CP3 CP1 CP2 AVCC RATEOUT SUMJ DNC VRATIO AGND TEMP ST2 ST1 PGND VDD Description HV Filter Capacitor, 100nF (±5%). Charge Pump Capacitor, 22 nF (±5%). Charge Pump Capacitor, 22 nF (±5%). Charge Pump Capacitor, 22 nF (±5%). Charge Pump Capacitor, 22 nF (±5%). Positive Analog Supply. Rate Signal Output. Output Amp Summing Junction. Do Not Connect to this Pin. Reference Supply for Ratiometric Output. Analog Supply Return. Temperature Voltage Output. Self-Test for Sensor 2. Self-Test for Sensor 1. Charge Pump Supply Return. Positive Charge Pump Supply. Rev. B | Page 5 of 12 ADXRS646 Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS N > 1000 for all typical performance plots, unless otherwise noted. 35 30 25 PERCENT OF POPULATION (%) 20 15 10 25 20 15 10 5 8.5 8.6 8.7 25 10.0 20 15 10 0.30 DRIFT (°/sec/°C) 09771-005 0.25 0.20 0.15 0.10 0.05 0 7.5 –50 –0.05 9.4 9.5 8.5 0 –0.10 9.3 9.0 8.0 –0.15 9.2 9.5 5 –0.20 9.1 –30 –10 10 30 50 70 90 110 TEMPERATURE (°C) Figure 5. Null Drift over Temperature 09771-105 SENSITIVITY (mV/°/sec) 10.5 –0.25 9.0 Figure 7. Sensitivity at 25°C 30 –0.30 PERCENT OF POPULATION (%) 8.9 SENSITIVITY (mV/°/sec) Figure 4. Null Bias at 25°C Figure 8. Sensitivity over Temperature, 16 Parts in Sockets 1k 3.5 ROOT ALLAN DEVIATION (°/Hour rms) 3.4 3.3 3.2 3.1 3.0 2.9 2.8 2.7 100 10 2.6 2.5 –60 –40 –20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) 09771-100 NULL (V) 8.8 09771-010 3.25 RATEOUT (V) 0 09771-004 3.20 3.15 3.10 3.05 3.00 2.95 2.90 2.85 2.80 2.75 0 5 Figure 6. Null Output over Temperature, 16 Parts in Sockets 1 0.01 0.1 1 10 100 1k AVERAGING TIME (Seconds) Figure 9. Typical Root Allan Deviation at 25°C vs. Averaging Time Rev. B | Page 6 of 12 09771-012 PERCENT OF POPULATION (%) 30 Data Sheet ADXRS646 –0.35 0.70 –0.40 0.65 –0.45 0.60 –0.50 –0.55 0.45 –0.65 0.40 –0.70 0.35 40 60 80 100 120 140 0.30 –60 TEMPERATURE (°C) –20 0 20 40 9 MAGNITUDE RESPONSE (dB) 40 30 20 10 –3 –2 –1 0 1 2 MISMATCH (%) Figure 12. Self-Test Mismatch at 25°C 3 4 PHASE 650 09771-007 630 590 570 610 120 140 0 –10 –20 3 –30 0 MAGNITUDE –3 –40 –6 –50 –9 –60 –12 –70 –15 –80 –18 0.1 09771-008 0 100 COUT = 470pF 6 60 50 80 Figure 14. ST2 Output Change vs. Temperature, 16 Parts in Sockets 70 –4 550 530 60 TEMPERATURE (°C) Figure 11. ST1 Output Change vs. Temperature, 16 Parts in Sockets PERCENT OF POPULATION (%) –40 1 FREQUENCY (kHz) –90 10 PHASE RESPONSE (Degrees) 20 09771-101 0 510 0.50 –0.60 –20 490 0.55 09771-103 ST2Δ (V) 0.75 09771-104 ST1Δ (V) Figure 13. ST2 Output Change at 25°C –0.30 –40 470 ST2Δ (mV) Figure 10. ST1 Output Change at 25°C –0.75 –60 450 0 350 –350 ST1Δ (mV) 5 09771-006 –370 –390 –410 –430 –450 –470 –490 –510 –530 –550 –570 –590 –610 0 –630 5 10 430 10 15 410 15 20 390 20 370 PERCENT OF POPULATION (%) 25 –650 PERCENT OF POPULATION (%) 25 Figure 15. ADXRS646 Frequency Response with a 2.2 kHz Output Filter Rev. B | Page 7 of 12 Data Sheet 35 70 30 60 50 40 30 20 20 15 10 09771-009 3.30 3.25 3.20 3.15 3.10 3.05 3.00 2.95 2.90 0 2.85 0 2.80 5 2.75 10 VTEMP OUTPUT (V) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0 50 100 TEMPERATURE (°C) 150 09771-102 0.5 –50 2.9 3.0 3.1 3.2 3.3 Figure 18. Current Consumption at 25°C 4.5 0 –100 2.8 CURRENT CONSUMPTION (mA) Figure 16. VTEMP Output at 25°C VTEMP (V) 25 Figure 17. VTEMP Output vs. Temperature Rev. B | Page 8 of 12 3.4 09771-013 PERCENT OF POPULATION (%) 80 2.70 PERCENT OF POPULATION (%) ADXRS646 Data Sheet ADXRS646 THEORY OF OPERATION The ADXRS646 operates on the principle of a resonator gyroscope. 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 produces 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. SETTING BANDWIDTH 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 signal 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. The rejection is achieved by mechanically 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. and can be well controlled because ROUT is trimmed during manufacturing to 180 kΩ ± 1%. Any external resistor applied between the RATEOUT pin (1B, 2A) and SUMJ pin (1C, 2C) results in The combination of an external capacitor (COUT) and the on-chip resistor (ROUT) creates a low-pass filter that limits the bandwidth of the ADXRS646 rate response. The −3 dB frequency set by ROUT and COUT is fOUT = 1/(2 × π × ROUT × COUT) ROUT = (180 kΩ × REXT)/(180 kΩ + REXT) An additional external filter is often added (in either hardware or software) to attenuate high frequency noise arising from demodulation spikes at the 18 kHz resonant frequency of the gyroscope. An RC output filter consisting of a 3.3 kΩ series resistor and 22 nF shunt capacitor (2.2 kHz pole) is recommended. TEMPERATURE OUTPUT AND CALIBRATION It is common practice to temperature-calibrate gyroscopes to improve their overall accuracy. The ADXRS646 has a temperature-dependent voltage output that provides input to such a calibration method. The temperature sensor structure is shown in Figure 20. The temperature output is characteristically 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. X Y Z VRATIO RFIXED Figure 19. Simplified Gyroscope Sensing Structure—One Corner The electrostatic 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 6D, Pin 7D). CP5 should not be grounded when power is applied to the ADXRS646. No damage occurs, but under certain conditions, the charge pump may fail to start up after the ground is removed without first removing power from the ADXRS646. Rev. B | Page 9 of 12 VTEMP RTEMP 09771-016 09771-015 The voltage at TEMP (3F, 3G) is nominally 2.9 V at 25°C, and VRATIO = 6 V. The temperature coefficient is 10 mV/°C (typical) at 25°C; the output response over the full temperature range is shown in Figure 17. Although the TEMP output is highly repeatable, it has only modest absolute accuracy. Figure 20. Temperature Sensor Structure ADXRS646 Data Sheet SUPPLY RATIOMETRICITY CONTINUOUS SELF-TEST The null output voltage (RATEOUT), sensitivity, self-test responses (ST1 and ST2), and temperature output (TEMP) of the ADXRS646 are ratiometric to VRATIO. Therefore, using the ADXRS646 with a supply-ratiometric ADC results in selfcancellation of errors resulting from minor supply variations. There remains a small, usually negligible, error due to nonratiometric behavior. Note that, to guarantee full measurement range, VRATIO should not be greater than AVCC. 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. NULL ADJUSTMENT The nominal 3.0 V null output voltage is true for a symmetrical swing range at RATEOUT (1B, 2A). However, an asymmetric 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 cause some null instability. Digital supply noise should be avoided, particularly in this case. 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. MODIFYING THE MEASUREMENT RANGE The ADXRS646 scale factor can be reduced to extend the measurement range to as much as ±450°/sec by adding a single 225 kΩ resistor between RATEOUT and SUMJ. If an external resistor is added between RATEOUT and SUMJ, COUT must be proportionally increased to maintain correct bandwidth. SELF-TEST FUNCTION The ADXRS646 includes a self-test feature that actuates each of the sensing structures and associated electronics in the same manner as if the gyroscope were subjected to angular rate. Self-test is activated by applying the standard logic high 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 mV (typical), and applying a logic high to Pin ST2 causes an opposite change of +450 mV (typical). The voltage applied to the ST1 and ST2 pins must never be greater than AVCC. 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 apparent null bias shift proportional to the degree of self-test mismatch. Rev. B | Page 10 of 12 Data Sheet ADXRS646 Gyroscopes are designed 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 error 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 20 Hz to 2 kHz. Performance is similar regardless of the direction of input vibration. 1 To further improve immunity to vibration and acceleration, 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. 0.12 0.10 0.08 0.06 (°/sec) IMMUNITY TO VIBRATION 0.04 0.02 0 0.1 –0.04 10 0.001 0.0001 0.00001 10 100 1k FREQUENCY (Hz) WITH VIBRATION 10k 09771-018 0.01 Figure 22. ADXRS646 Sine Vibration Output Response (5 g, 20 Hz to 5 kHz); Gyroscope Bandwidth Set to 1600 Hz NO VIBRATION 100 1k FREQUENCY (Hz) 10k 09771-017 (°/sec)2/ Hz –0.02 Figure 21. ADXRS646 Output Response With and Without Random Vibration (15 g RMS, 20 Hz to 2 kHz); Gyroscope Bandwidth Set to 1600 Hz Rev. B | Page 11 of 12 ADXRS646 Data Sheet OUTLINE DIMENSIONS A1 BALL CORNER 7.05 6.85 SQ 6.70 7 6 5 4 3 2 *A1 CORNER INDEX AREA 1 A B 4.80 BSC SQ 0.80 BSC C D E F G TOP VIEW BOTTOM VIEW DETAIL A 3.80 MAX SEATING PLANE 0.60 0.55 0.50 BALL DIAMETER 3.20 MAX 2.50 MIN COPLANARITY 0.15 *BALL A1 IDENTIFIER IS GOLD PLATED AND CONNECTED TO THE D/A PAD INTERNALLY VIA HOLES. 07-11-2012-B DETAIL A 0.60 MAX 0.25 MIN Figure 23. 32-Lead Ceramic Ball Grid Array [CBGA] (BG-32-3) Dimensions shown in millimeters ORDERING GUIDE Model 1 ADXRS646BBGZ ADXRS646BBGZ-RL EVAL-ADXRS646Z 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 Z = RoHS Compliant Part. ©2011–2014 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D09771-0-1/14(B) Rev. B | Page 12 of 12 Package Option BG-32-3 BG-32-3