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250/sec Yaw Rate Gyro
ADXRS612
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 105C operation Self-test on digital command Ultrasmall and light (<0.15 cc, <0.5 gram) Temperature sensor output RoHS compliant
GENERAL DESCRIPTION
The ADXRS612 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 the same high volume BIMOS process used for high reliability automotive airbag accelerometers. 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 output is ratiometric with respect to a provided reference supply. A single external resistor can be used to lower the scale factor. An external capacitor is used to set the bandwidth. 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 ADXRS612 is available in a 7 mm x 7 mm x 3 mm BGA chip-scale package.
APPLICATIONS
Vehicle chassis rollover sensing Inertial measurement units Platform stabilization
FUNCTIONAL BLOCK DIAGRAM
+5V (ADC REF) 100nF
+5V AVCC 100nF AGND
ST2
ST1
TEMP
VRATIO 25k
ADXRS612
SELF-TEST
25k @ 25C
DEMOD
DRIVE AMP
MECHANICAL SENSOR
AC AMP
VGA
+5V
VDD
180k 1% CHARGE PUMP AND VOLTAGE REGULATOR CP1 CP2 CP3 CP4 CP5 SUMJ 100nF 22nF 22nF COUT RATEOUT
06521-001
100nF PGND
Figure 1.
Rev. 0
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)2007 Analog Devices, Inc. All rights reserved.
ADXRS612 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Functional Block Diagram .............................................................. 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 4 Rate Sensitive Axis ....................................................................... 4 ESD Caution.................................................................................. 4 Pin Configuration and Function Descriptions............................. 5 Typical Performance Characteristics ............................................. 6 Theory of Operation .........................................................................9 Setting Bandwidth.........................................................................9 Temperature Output and Calibration.........................................9 Calibrated Performance................................................................9 ADXRS612 and Supply Ratiometricity ................................... 10 Null Adjustment ......................................................................... 10 Self-Test Function ...................................................................... 10 Continuous Self-Test.................................................................. 10 Outline Dimensions ....................................................................... 11 Ordering Guide .......................................................................... 11
REVISION HISTORY
3/07--Revision 0: Initial Version
Rev. 0 | Page 2 of 12
ADXRS612 SPECIFICATIONS
All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed. TA = -40C to +105C, 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 SENSITIVITY 1 Measurement Range 2 Initial and Over Temperature Temperature Drift 3 Nonlinearity NULL1 Null Linear Acceleration Effect NOISE PERFORMANCE Rate Noise Density 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 25C Scale Factor 6 Load to VS Load to Common TURN-ON TIME OUTPUT DRIVE CAPABILITY Current Drive Capacitive Load Drive POWER SUPPLY Operating Voltage (VS) Quiescent Supply Current TEMPERATURE RANGE Specified Performance
1 2
Conditions Clockwise rotation is positive output Full-scale range over specifications range -40C to +105C Best fit straight line -40C to +105C Any axis TA 25C
Min 250 6.2
ADXRS612BBGZ Typ Max 300 7.0 2 0.1 2.5 0.1 0.06
Unit /sec mV//sec % % of FS V /sec/g /sec/Hz
7.8
2.15
2.85
0.01 12 ST1 pin from Logic 0 to Logic 1 ST2 pin from Logic 0 to Logic 1 -750 300 -5 3.3 40 2.35
14.5 -525 525
2500 17 -300 750 +5 1.7 100 2.65
Hz kHz mV mV % V V k V mV/C
To common Load = 10 M @ 25C, VRATIO = 5 V
50 2.5 9 25 25
k
50 200 1000 k ms A pF V mA C
Power on to 1/2/sec of final For rated specifications
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. 3 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.
Rev. 0 | Page 3 of 12
ADXRS612 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 2000 g 2000 g -0.3 V to +6.0 V AVCC AVCC Indefinite -55C to +125C -65C to +150C
A1 ABCDE FG LATERAL AXIS
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 GND VRATIO/2 RATE IN
06521-002
RATE OUT
4.75V
0.25V
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 2000 g and can exceed the absolute maximum rating of the device. Care should be exercised in handling to avoid damage.
Figure 2. RATEOUT Signal Increases with Clockwise Rotation
ESD CAUTION
Rev. 0 | Page 4 of 12
ADXRS612 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
06521-023
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, 0.1 F. 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. 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. 0 | Page 5 of 12
ADXRS612 TYPICAL PERFORMANCE CHARACTERISTICS
N > 1000 for all typical performance plots, unless otherwise noted.
16 14
25
20
12 10 8 6 4
% OF POPULATION
% OF POPULATION
15
10
5
2 0
06521-003
-7 -6 -5 -4 -3 -2 -1
0
1
2
3
4
5
6
7
VOLTS
% DRIFT
Figure 4. Null Output at 25C (VRATIO = 5 V)
25
Figure 7. Sensitivity Drift over Temperature
45 40
20
% OF POPULATION
35
% OF POPULATION
30 25 20 15 10 5 -675 -625 -575 -525 (mV) -475 -425 -375
06521-007 06521-008
15
10
5
0
0.05
0.10
0.15
0.20
0.25
-0.30
-0.25
-0.20
-0.15
-0.10
-0.05
0.30
0
0
06521-004
(/sec/C)
Figure 5. Null Drift over Temperature (VRATIO = 5 V)
30 45 40 25 35
% OF POPULATION % OF POPULATION
Figure 8. ST1 Output Change at 25C (VRATIO = 5 V)
20
30 25 20 15 10
15
10
5 5
06521-005
0 6.3 6.4 6.5 6.6 6.7 6.8 6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 (mV//sec)
0
375 400 425 450 475 500 525 550 575 600 625 650 675 (mV)
Figure 6. Sensitivity at 25C (VRATIO = 5 V)
Figure 9. ST2 Output Change at 25C (VRATIO = 5 V)
Rev. 0 | Page 6 of 12
06521-006
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
0
ADXRS612
50 45 40
30 40 35
% OF POPULATION
% OF POPULATION
06521-009
35 30 25 20 15 10 5 0 -5 -4 -3 -2 -1 0 1 2 3 4 5 % MISMATCH
25 20 15 10 5 0
VOLTS
Figure 10. Self-Test Mismatch at 25C (VRATIO = 5 V)
800 600 400 200 0 -200 -400 ST1 -600 -800 -40 ST2
Figure 13. VTEMP Output at 25C (VRATIO = 5 V)
3.3 3.1 2.9 2.7
VOLTS
(mV)
2.5 2.3 2.1 1.9 1.7 256 PARTS
06521-013
06521-014
-20
0
20
40
60
80
100
120
06521-010
1.5 -40
-20
0
20
40
60
80
100
120
TEMPERATURE (C)
TEMPERATURE (C)
Figure 11. Typical Self-Test Change over Temperature
40 35 30
Figure 14. VTEMP Output over Temperature, 256 Parts (VRATIO = 5 V)
60 REF 50 40 30 20 10 0 -10 -20 750 Y X +45 -45
% OF POPULATION
20 15 10 5 0
06521-011
g OR /sec
25
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
770
790 TIME (ms)
810
830
850
(mA)
Figure 12. Current Consumption at 25C (VRATIO = 5 V)
Figure 15. g and g x g Sensitivity for a 50 g, 10 ms Pulse
Rev. 0 | Page 7 of 12
06521-012
2.40 2.42 2.44 2.46 2.48 2.50 2.52 2.54 2.56 2.58 2.60
ADXRS612
1.6 1.4 1.2 1.0 0.05 0.10
(/sec)
0.8 0.6 0.4 LAT 0.2 0 100 LONG RATE
06521-015
(/sec)
0
-0.05
1k (Hz)
10k
0
20
40
60
80
100
120
140
TIME (Hours)
Figure 16. Typical Response to 10 g Sinusoidal Vibration (Sensor Bandwidth = 2 kHz)
400 300 200 100 DUT1 OFFSET BY +200/sec
Figure 19. Typical Shift in 90 sec Null Averages Accumulated over 140 Hours
0.10
0.05
(/sec)
(/sec)
0 -100 -200 -300 DUT2 OFFSET BY -200/sec
0
-0.05
0
50
100 (ms)
150
200
250
06521-016
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
0.01
06521-017
0.1
1
10
100
1k
10k
100k
100
1k (Hz)
10k
100k
AVERAGING TIME (Seconds)
Figure 18. Typical Root Allan Deviation at 25C vs. Averaging Time
Figure 21. Typical Noise Spectral Density (Bandwidth = 40 Hz)
Rev. 0 | Page 8 of 12
06521-020
0.001 0.01
(/sec/ Hz rms)
0.1
0.01
(/sec rms)
0.001
0.0001 10
06521-019
-400
-0.10
06521-018
-0.10
ADXRS612 THEORY OF OPERATION
The ADXRS612 operates on the principle of a resonator gyro. 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 during angular rate. 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 the 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 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 ADXRS612. 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 ADXRS612.
0.1 0.01
(/sec/ Hz rms)
0.001
0.0001
0.00001
100
1k (Hz)
10k
100k
Figure 22. Noise Spectral Density with Additional 250 Hz Filter
TEMPERATURE OUTPUT AND CALIBRATION
It is common practice to temperature-calibrate gyros to improve their overall accuracy. The ADXRS612 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 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 VTEMP RTEMP
06521-022
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 ADXRS612 rate response. The -3 dB frequency set by ROUT and COUT is
f OUT = 1/(2 x x ROUT x 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
RFIXED
ROUT = (180 k x REXT )/(180 k + REXT )
Figure 23. ADXRS612 Temperature Sensor Structure
CALIBRATED PERFORMANCE
Using a 3-point calibration technique, it is possible to calibrate the ADXRS612 null and sensitivity drift 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.
In general, an additional filter (in either hardware or software) is added to attenuate high frequency noise arising from demodulation spikes at the 14 kHz resonant frequency of the gyro. The noise spikes at 14 kHz can be clearly seen in the power spectral density curve, shown in Figure 21. Normally, this additional filter corner frequency is set to greater than five times the required bandwidth to preserve good phase response. Figure 22 shows the effect of adding a 250 Hz filter to the output of an ADXRS612 set to 40 Hz bandwidth (as shown in Figure 21). High frequency demodulation artifacts are attenuated by approximately 18 dB.
Rev. 0 | Page 9 of 12
06521-021
0.000001 10
ADXRS612
ADXRS612 AND SUPPLY RATIOMETRICITY
The ADXRS612 RATEOUT and TEMP signals are ratiometric to the VRATIO voltage; that is, the null voltage, rate sensitivity, and temperature outputs are proportional to VRATIO. So the ADXRS612 is most easily used with a supply-ratiometric analog-to-digital converter, which 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, self-test, 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 = 4.75 V -0.4% 0.6% -0.4% 0.6% -0.04% 0.3% 0.03% 0.1% -0.3% 0.1% VS = VRATIO = 5.25 V -0.3% 0.6% -0.3% 0.6% -0.02% 0.2% 0.1% 0.1% -0.5% 0.1%
SELF-TEST FUNCTION
The ADXRS612 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 -0.5 V, and ST2 causes an opposite change of +0.5 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 equal to VRATIO to the ST1 pin and the ST2 pin. The voltage applied to ST1 and ST2 must never be greater than AVCC.
CONTINUOUS SELF-TEST
The on-chip integration of the ADXRS612 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 a separate application note.
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.
Rev. 0 | Page 10 of 12
ADXRS612 OUTLINE DIMENSIONS
7.05 6.85 SQ 6.70 *A1 CORNER INDEX AREA
7 6 5 4 3 2 1 A B
A1 BALL PAD INDICATOR TOP VIEW 4.80 BSC SQ
BOTTOM VIEW
C D E F G
DETAIL A 3.80 MAX
(BALL PITCH)
0.80 BSC
DETAIL A
0.60 0.25
3.30 MAX 2.50 MIN
SEATING PLANE
0.60 0.55 0.50 BALL DIAMETER
COPLANARITY 0.15
*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
Model ADXRS612BBGZ 1 ADXRS612BBGZ-RL1
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]
060506-A
Package Option BG-32-3 BG-32-3
Z = RoHS Compliant Part.
Rev. 0 | Page 11 of 12
ADXRS612 NOTES
(c)2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06521-0-3/07(0)
Rev. 0 | Page 12 of 12

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