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Vibration Rejecting 250/s Yaw Rate Gyro
Preliminary Technical Data
FEATURES
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 wide frequency 10,000 g powered shock survivability Ratiometric to referenced supply 5 V single-supply operation -40C to +105C operation Self-test on digital command Ultrasmall and light (<0.15 cc, <0.5 gram) Temperature sensor output RoHS compliant
ADXRS642
GENERAL DESCRIPTION
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. 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 x 7 mm x 3 mm BGA chip-scale package.
APPLICATIONS
Industrial applications Inertial Measurement Units Severe Mechanical Environments Platform stabilization
FUNCTIONAL BLOCK DIAGRAM
3 to 5V (ADC REF) 100nF 5V AV CC 100nF AGND SELF-TEST 25k @ 25C
ST2
ST1
TEMP
VRATIO 25k
ADXRS642
DEMOD
DRIVE AMP
MECHANICAL SENSOR
AC AMP
VGA
5V
VDD CHARGE PUMP AND VOLTAGE REGULATOR SUMJ 100nF 22nF 22nF COUT
180k 1%
100nF
PGND
CP1 CP2 CP3 CP4 CP5
RATEOUT
08820-001
Figure 1. Block Diagram
Rev. Pr A
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 (c)201 Analog Devices, Inc. All rights reserved.
ADXRS642 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications ....................................................................................... 1 General Description ......................................................................... 1 Functional Block Diagram .............................................................. 1 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 4 Rate Sensitive Axis ....................................................................... 4 ESD Caution .................................................................................. 4 Pin Configuration and Function Descriptions ............................. 5 Theory of Operation ........................................................................ 6
Preliminary Technical Data
Setting Bandwidth .........................................................................6 Temperature Output and Calibration .........................................6 Supply Ratiometricity ...................................................................6 Modifying the measurement range .............................................7 Null Adjustment ............................................................................8 Self-Test Function .........................................................................8 Continuous Self-Test .....................................................................8 mechanical performance ..............................................................8 Outline Dimensions ..........................................................................9 Ordering Guide .............................................................................9
Rev. Pr. A | Page 2 of 10
Preliminary Technical Data SPECIFICATIONS
All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed.
ADXRS642
TA = 25C, VS = AVCC = VDD = 5 V, VRATIO = AVCC, angular rate = 0/sec, bandwidth = 80 Hz (COUT = 0.01 F), IOUT = 100 A, 1 g, unless otherwise noted. Table 1.
Parameter SENSITIVITY1 Measurement Range2 Initial and Over Temperature Temperature Drift3 Nonlinearity NULL1 Null Calibrated Null7 Temperature Drift Linear Acceleration Effect Vibration Rectification NOISE PERFORMANCE Rate Noise Density Resolution Floor FREQUENCY RESPONSE Bandwidth4 Sensor Resonant Frequency SELF-TEST1 ST1 RATEOUT Response ST2 RATEOUT Response ST1 to ST2 Mismatch5 Logic 1 Input Voltage Logic 0 Input Voltage Input Impedance TEMPERATURE SENSOR1 VOUT at 25C Scale Factor6 Load to VS Load to Common TURN-ON TIME7 OUTPUT DRIVE CAPABILITY Current Drive Capacitive Load Drive POWER SUPPLY Operating Voltage (VS) Quiescent Supply Current TEMPERATURE RANGE Specified Performance
1 2 3
Conditions Clockwise rotation is positive output Full-scale range over specifications range -40C to +105C Best fit straight line -40C to +105C -40C to +105C -40C to +105C Any axis 25g RMS, 50Hz to 5kHz TA 25C TA = 25C 1 minute to 1 hour in-run +3dB user adjustable up to
Min 250
Typ 300 7.0 2 0.01 2.5 0.1 1 0.03 0.0002 0.02 20 2000 18 -45 45 2
Max
Unit /sec mV//sec % % of FS V /sec /sec /sec/g /s/g2 /sec/Hz /hr Hz kHz /sec /sec % V V k V mV/C k k ms A pF V mA C
16 ST1 pin from Logic 0 to Logic 1 ST2 pin from Logic 0 to Logic 1 -5 3.3 To common Load = 10 M 25C, VRATIO = 5 V 40 2.35
20
5 1.7 100 2.65
50 2.5 9 25 25
Power on to 0.5/s of final with CP5 = 100nF For rated specifications
50 200 1000 4.75 5.00 3.5 5.25 4.5 +105
-40
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 +25C to -40C or +25C to +105C. 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 Scale factor for a change in temperature from 25C to 26C. VTEMP is ratiometric to VRATIO. See the Temperature Output and Calibration section for more information. 7 Based on characterization
Rev. Pr. A | Page 3 of 10
ADXRS642 ABSOLUTE MAXIMUM RATINGS
Table 2.
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 3,000 g 3,000 g -0.3 V to +6.0 V AVCC AVCC Indefinite -55C to +125C -65C to +150C
Preliminary Technical Data
RATE SENSITIVE AXIS
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 VCC = 5V LONGITUDINAL AXIS + 7 1 A1 ABCDE FG LATERAL AXIS GND VRATIO/2 RATE IN
08820-002
RATE OUT
4.75V
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.
0.25V
Figure 2. RATEOUT Signal Increases with Clockwise Rotation
ESD CAUTION
Rev. Pr. A | Page 4 of 10
Preliminary Technical Data PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
PGND VDD CP5 CP3 CP4 7 6 ST1 ST2 TEMP CP1 CP2 AVCC 5 4 3 2 1 VRATIO G F E NC D SUMJ C B A
08820-023
ADXRS642
AGND
RATEOUT
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, 100nF. 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. Do Not Connect. 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. Pr. A | Page 5 of 10
ADXRS642 THEORY OF OPERATION
The ADXRS642 operates on the principle of a resonator gyro. Figure 4 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. 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.
Preliminary Technical Data
SETTING BANDWIDTH
External Capacitor COUT is used in combination with the onchip ROUT resistor 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
f OUT 1/2 ROUT COUT
and can be well controlled because ROUT has been trimmed during manufacturing to be 180 k 1%. Any external resistor applied between the RATEOUT pin (1B, 2A) and SUMJ pin (1C, 2C) results in
ROUT 180 k REXT /180 k 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 22nF shunt capacitor (2.2kHz pole) is recommended.
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 . 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. The voltage at TEMP (3F, 3G) is nominally 2.5 V at 25C, and VRATIO = 5 V. The temperature coefficient is ~9 mV/C at 25C. Although the TEMP output is highly repeatable, it has only modest absolute accuracy.
VRATIO
08952-011
X
Y Z
VTEMP
08820-022
RFIXED
RTEMP
Figure 4. Simplified Gyro Sensing Structure - One Corner
Figure 5. Temperature Sensor Structure
The electrostatic resonator requires 18 to 20V for operation. Because only 5V are typically available in most applications, a charge pump is included on chip. If an external 18 to 20V 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 AD642's RATEOUT, ST1, ST2, and TEMP signals are ratiometric to the VRATIO voltage, i.e., the null voltage, rate sensitivity, and temperature outputs are proportional to VRATIO. So, 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 non-ratiometric behavior. Note that, in order to guarantee full rate range, VRATIO should not be greater than AVCC
Rev. Pr. A | Page 6 of 10
Preliminary Technical Data
MODIFYING THE MEASUREMENT RANGE
The ADXRS642 scale factor can be reduced to extend the measurement range to as much as 450/s by adding a single 225k resistor between the RATEOUT and SUMJ. If an external resistor is added between RATEOUT and SUMJ COUT must be proportionally reduced to maintain correct bandwidth.
ADXRS642
Rev. Pr. A | Page 7 of 10
ADXRS642
NULL ADJUSTMENT
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.
Preliminary Technical Data
response with and without 15g RMS 50Hz to 5kHz of random vibration. Bandwidth of the gyro was limited to 1600Hz. Performance is similar regardless of the direction of input vibration.
1
0.1
(/s) /root Hz
0.01
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.
2
0.001
0.0001
0.00001 10 100 1000 10000
Frequency
Figure 6. ADXRS642 Output Response With and Without Random Vibration (15g RMS, 50Hz to 5kHz)
Figure 7 demonstrates the ADXRS642 DC bias response to 5g Sine vibration over the 20Hz to 5kHz range. As can be seen, there are no sensitive frequencies present and vibration rectification is vanishingly small. As in the previous example gyro bandwidth was set to 1600Hz.
0.12
CONTINUOUS SELF-TEST
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.
deg/sec
0.1 0.08 0.06 0.04 0.02 0 0.02 0.04 10 100 Hz 1000 10000
MECHANICAL PERFORMANCE
The ADXRS642 excellent vibration rejection is demonstrated in the graphs below. Figure 6 shows the ADXRS642 output
Figure 7. ADXRS642 Sine Vibration Output Response (5g, 20Hz to 5kHz)
Rev. Pr. A | Page 8 of 10
Preliminary Technical Data OUTLINE DIMENSIONS
A1 BALL CORNER 7.05 6.85 SQ 6.70 *A1 CORNER INDEX AREA
7 6 5 4 3 2 1
ADXRS642
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 8. 32-Lead Ceramic Ball Grid Array [CBGA] (BC-32-3) Dimensions shown in millimeters
ORDERING GUIDE
Model1 ADXRS642BBGZ ADXRS642BBGZ-RL EVAL-ADXRS642Z
1
Temperature Range -40C to +105C -40C to +105C
Package Description 32-Lead Ceramic Ball Grid Array [CBGA] 32-Lead Ceramic Ball Grid Array [CBGA] Evaluation Board
10-26-2009-B
Package Option BC-32-3 BC-32-3
Z = RoHS Compliant Part.
Rev. Pr. A | Page 9 of 10
ADXRS642 NOTES
Preliminary Technical Data
(c)2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. PR09770-0-2/11(PrA)
Rev. PrA | Page 10 of 10

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