Vibration Rejecting ±250°/s Yaw Rate Gyroscope ADXRS642 Data Sheet FEATURES GENERAL DESCRIPTION Complete rate gyroscope on a single chip Z-axis (yaw rate) response 20°/hour bias stability 0.02°/√second angle random walk High vibration rejection over a wide frequency 10,000 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 (<0.15 cc, <0.5 gram) Temperature sensor output RoHS compliant The ADXRS642 is a complete angular rate sensor (gyroscope) that uses the Analog Devices, Inc., surface-micromachining process to make a functionally complete and low cost angular rate sensor integrated with all of the required electronics on one chip. The manufacturing technique for this device is a patented high volume BiMOS process with years of proven field reliability. The ADXRS642 is an industrial grade gyroscope that is 100% pin, package, temperature, and function compatible with the ADXRS622 and ADXRS652, while offering enhanced vibration rejection The output signal, RATEOUT (1B, 2A), 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°/s. The output is ratiometric with respect to a provided reference supply. Other external capacitors are required for operation. APPLICATIONS Industrial applications Inertial measurement units 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 ADXRS642 is available in a 7 mm × 7 mm × 3 mm BGA chip-scale package. FUNCTIONAL BLOCK DIAGRAM 3V TO 5V (ADC REF) 100nF 5V ST2 ST1 TEMP AVCC 100nF SELF-TEST 25kΩ @ 25°C VRATIO ADXRS642 25kΩ AGND DEMOD MECHANICAL SENSOR DRIVE AMP 5V AC AMP VGA 180kΩ ±1% VDD CHARGE PUMP AND VOLTAGE REGULATOR 100nF PGND SUMJ RATEOUT 100nF 22nF 22nF COUT 09770-001 CP1 CP2 CP3 CP4 CP5 Figure 1. Rev. A 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 ©2011–2012 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com ADXRS642 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Theory of Operation .........................................................................8 Applications ....................................................................................... 1 Setting Bandwidth .........................................................................8 General Description ......................................................................... 1 Temperature Output and Calibration .........................................8 Functional Block Diagram .............................................................. 1 Supply Ratiometricity ...................................................................8 Revision History ............................................................................... 2 Modifying the Measurement Range ...........................................9 Specifications..................................................................................... 3 Null Adjustment ............................................................................9 Absolute Maximum Ratings ............................................................ 4 Self-Test Function .........................................................................9 Rate Sensitive Axis ....................................................................... 4 Continuous Self-Test.....................................................................9 ESD Caution .................................................................................. 4 Mechanical Performance ..............................................................9 Pin Configuration and Function Descriptions ............................. 5 Outline Dimensions ....................................................................... 10 Typical Performance Characteristics ............................................. 6 Ordering Guide .......................................................................... 10 REVISION HISTORY 10/12—Rev. 0 to Rev. A Changes to Figure 1 .......................................................................... 1 Changes to Figure 10 ........................................................................ 7 Updated Outline Dimensions ....................................................... 10 4/11—Revision 0: Initial Version Rev. A | Page 2 of 12 Data Sheet ADXRS642 SPECIFICATIONS All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed. TA = 25°C, VS = AVCC = VDD = 5 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 and Over Temperature Temperature Drift 3 Nonlinearity NULL1 Null Calibrated Null 4 Temperature Drift Linear Acceleration Effect Vibration Rectification NOISE PERFORMANCE Rate Noise Density Resolution Floor FREQUENCY RESPONSE Bandwidth 5 Sensor Resonant Frequency SELF-TEST1 ST1 RATEOUT Response ST2 RATEOUT Response ST1 to ST2 Mismatch 6 Logic 1 Input Voltage Logic 0 Input Voltage Input Impedance TEMPERATURE SENSOR1 VOUT at 25°C Scale Factor 7 Load to VS Load to Common TURN-ON TIME4 OUTPUT DRIVE CAPABILITY Current Drive Capacitive Load Drive POWER SUPPLY Operating Voltage (VS) Quiescent Supply Current TEMPERATURE RANGE Specified Performance Conditions Clockwise rotation is positive output Full-scale range over specifications range −40°C to +105°C Min Typ ±250 Best fit straight line ±300 7.0 ±2 0.01 °/sec mV/°/sec % % of FS −40°C to +105°C −40°C to +105°C −40°C to +105°C Any axis 25 g rms, 50 Hz to 5 kHz 2.5 ±0.1 ±1 0.03 0.0002 V °/sec °/sec °/sec/g °/s/g2 TA ≤ 25°C TA = 25°C 1 minute to 1 hour in-run 0.02 20 °/sec/√Hz °/hr +3 dB user adjustable up to specification 15 ST1 pin from Logic 0 to Logic 1 ST2 pin from Logic 0 to Logic 1 −5 3.3 2000 17 Max 19 −45 45 ±2 +5 1.7 100 To common 40 50 Load = 10 MΩ 25°C, VRATIO = 5 V 2.35 2.5 9 25 25 Hz kHz °/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 5.25 4.5 V mA +105 °C 4.75 −40 1 5.00 3.5 2.65 Unit 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 Based on characterization. 5 Adjusted by external capacitor, COUT. 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). 7 Scale factor for a change in temperature from 25°C to 26°C. VTEMP is ratiometric to VRATIO. See the Temperature Output and Calibration section for more information. 2 3 Rev. A | Page 3 of 12 ADXRS642 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 +6.0 V AVCC AVCC Indefinite −55°C to +125°C −65°C to +150°C 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. 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 VCC = 5V LONGITUDINAL AXIS 4.75V + VRATIO /2 7 RATE IN 1 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. A | Page 4 of 12 09770-002 Table 2. Data Sheet ADXRS642 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS VDD PGND CP5 CP3 CP4 7 6 ST1 CP1 5 ST2 CP2 4 AVCC 3 TEMP 2 AGND G F VRATIO NC SUMJ E D C RATEOUT B A 09770-004 1 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 NC VRATIO AGND TEMP ST2 ST1 PGND VDD Description HV Filter Capacitor, 100 nF. Charge Pump Capacitor, 22 nF. Charge Pump Capacitor, 22 nF. Charge Pump Capacitor, 22 nF. Charge Pump Capacitor, 22 nF. Positive Analog Supply. Rate Signal Output. Output Amp Summing Junction. No Connection. Do not connect to these pins. 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. A | Page 5 of 12 ADXRS642 Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS 50 60 PERCENTAGE OF POPULATION (%) PERCENTAGE OF POPULATION (%) 45 50 40 30 20 10 40 35 30 25 20 15 10 2.20 2.25 2.30 2.35 2.40 2.45 2.50 2.55 2.60 2.65 2.70 2.75 2.80 NULL BIAS (V) 0 09770-005 0 –4 –3 –2 –1 0 1 3 2 4 MISMATCH (%) Figure 4. Null Bias at 25°C 09770-008 5 Figure 7. Self- Test Mismatch at 25°C (VRATIO = 5 V) 100 60 PERCENTAGE OF POPULATION (%) PERCENTAGE OF POPULATION (%) 90 50 40 30 20 10 80 70 60 50 40 30 20 ST1 Δ (mV) 0 09770-006 –600 –560 –520 –480 –440 –400 –360 –320 –280 –240 –200 2.36 2.38 2.40 2.42 2.44 2.46 2.48 2.50 VTEMP OUTPUT (V) 09770-009 10 0 Figure 8. VTEMP Output at 25°C (VRATIO = 5 V) Figure 5. ST1 Output Change at 25°C (VRATIO = 5 V) 100 60 PERCENTAGE OF POPULATION (%) 40 30 20 10 80 70 60 50 40 30 20 0 240 280 320 360 400 440 480 520 560 600 ST2 Δ (mV) 640 0 0.0056 0.0060 0.0064 0.0068 0.0072 0.0076 0.0080 0.0084 0.0088 SENSITIVITY (mV/°/s) Figure 9. Sensitivity at 25°C Figure 6. ST2 Output Change at 25°C (VRATIO = 5 V) Rev. A | Page 6 of 12 09770-010 10 09770-007 PERCENTAGE OF POPULATION (%) 90 50 Data Sheet ADXRS642 3.3 3.1 2.9 VTEMP OUTPUT (V) ROOT ALLAN DEVIATION (°/Hour rms) 1000 100 2.7 2.5 2.3 2.1 1.9 1 10 100 1000 10000 AVERAGING TIME (Seconds) 50 40 30 20 10 CURRENT CONSUMPTION (mA) 09770-012 PERCENTAGE OF POPULATION (%) 60 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.55 3.60 3.65 3.70 3.75 –25 0 25 50 75 100 TEMPERATURE (°C) Figure 12. VTEMP Output over Temperature, 256 Parts (VRATIO = 5 V) Figure 10. Typical Root Allan Deviation at 25°C vs. Averaging Time 0 1.5 –50 Figure 11. Current Consumption at 25°C (VRATIO = 5 V) Rev. A | Page 7 of 12 09770-013 0.1 09770-011 1.7 10 0.01 ADXRS642 Data Sheet THEORY OF OPERATION The ADXRS642 operates on the principle of a resonator gyro. Figure 13 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 ADXRS642 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 and vibration. This 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 ADXRS642. and can be well controlled because ROUT has been trimmed during manufacturing to be 180 kΩ ± 1%. Any external resistor applied between the RATEOUT pin (1B, 2A) and SUMJ pin (1C, 2C) results in The external capacitor, COUT, is used in combination with the on-chip resistor, ROUT, to create a low-pass filter to limit the bandwidth of the ADXRS642 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 ) In general, an additional filter (in either hardware or software) is added to attenuate high frequency noise arising from demodulation spikes at the 18 kHz resonant frequency of the gyro. An R/C output filter consisting of a 3.3k series resistor and 22 nF shunt capacitor (2.2 kHz pole) is recommended. Figure 13 shows the effect of adding this filter to the output of an ADXRS642 set to a 2000 Hz bandwidth. TEMPERATURE OUTPUT AND CALIBRATION It is common practice to temperature-calibrate gyros to improve their overall accuracy. The ADXRS642 has a temperature proportional voltage output that provides input to such a calibration method. The temperature sensor structure is shown in Figure 14. 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 The voltage at TEMP (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. RFIXED VTEMP RTEMP 09770-003 09770-016 VRATIO Figure 14. Temperature Sensor Structure Figure 13. Simplified Gyro Sensing Structure–One Corner 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 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 ADXRS642. 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 ADXRS642. SUPPLY RATIOMETRICITY The ADXRS642 RATEOUT, ST1, ST2, and TEMP signals are ratiometric to the VRATIO voltage; for example, the null voltage, rate sensitivity and temperature outputs are proportional to VRATIO. Therefore, it is most easily used with a supply-ratiometric ADC, which results in self-cancellation of errors due to minor supply variations. There is some small, usually negligible, error due to nonratiometric behavior. Note that to guarantee full rate range, VRATIO should not be greater than AVCC. Rev. A | Page 8 of 12 Data Sheet ADXRS642 MODIFYING THE MEASUREMENT RANGE MECHANICAL PERFORMANCE The ADXRS642 scale factor can be reduced to extend the measurement range to as much as ±450°/sec by adding a single 225 kΩ resistor between the RATEOUT and SUMJ. If an external resistor is added between RATEOUT and SUMJ, COUT must be proportionally reduced to maintain the correct bandwidth. The ADXRS642 excellent vibration rejection is demonstrated in Figure 15 and Figure 16. Figure 15 shows the ADXRS642 output response with and without 15 g rms 50 Hz to 5 kHz of random vibration. The bandwidth of the gyro was limited to 1600 Hz. Performance is similar regardless of the direction of the input vibration. SELF-TEST FUNCTION The ADXRS642 includes a self-test feature that actuates each of the sensing structures and associated electronics in the same manner, 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 −0.3 V, and ST2 causes an opposite change of +0.3 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 (±2%), 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 equal to VRATIO to the ST1 pin and the ST2 pin. The voltage applied to ST1 and ST2 must never be greater than AVCC. 1 0.1 0.01 0.001 0.0001 0.00001 10 100 1k 10k FREQUENCY (Hz) 09770-014 The nominal 2.5 V null is for a symmetrical swing range at RATEOUT (1B, 2A). However, a nonsymmetric 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. (°/s)2/√Hz NULL ADJUSTMENT Figure 15. ADXRS642 Output Response with and Without Random Vibration (15 g rms, 50 Hz to 5 kHz) Figure 16 demonstrates the ADXRS642 dc noise response to 5g sine vibration over the 20 Hz to 5 kHz range. As can be seen, there are no sensitive frequencies present, and vibration rectification is vanishingly small. As in the previous example, the gyro bandwidth was set to 1600 Hz. 0.12 CONTINUOUS SELF-TEST 0.10 0.08 0.06 (°/s) The on-chip integration of the ADXRS642 gives it higher reliability than is obtainable with any other high volume manufacturing method. Also, it is manufactured under a mature BiMOS process that has field-proven reliability. As an additional failure detection measure, power-on self-test can be performed. However, some applications may warrant continuous self-test while sensing rate. Details outlining continuous self-test techniques are also available in the AN-768 Application Note. 0.04 0.02 0 –0.04 10 100 1k 10k FREQUENCY (Hz) Figure 16. ADXRS642 Sine Vibration Noise Response (5 g, 20 Hz to 5 kHz) Rev. A | Page 9 of 12 09770-015 –0.02 ADXRS642 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 17. 32-Lead Ceramic Ball Grid Array [CBGA] (BG-32-3) Dimensions shown in millimeters ORDERING GUIDE Model1 ADXRS642BBGZ ADXRS642BBGZ-RL EVAL-ADXRS642Z 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. Rev. A | Page 10 of 12 Package Option BG-32-3 BG-32-3 Data Sheet ADXRS642 NOTES Rev. A | Page 11 of 12 ADXRS642 Data Sheet NOTES ©2011–2012 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D09770-0-10/12(A) Rev. A | Page 12 of 12