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50/s Yaw Rate Gyro
ADXRS624
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 Qualified for automotive applications
GENERAL DESCRIPTION The ADXRS624 is a complete angular rate sensor (gyroscope)
that uses the Analog Devices, Inc., surface-micromachining process to create a functionally complete and low cost angular rate sensor integrated with all 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 between SUMJ and RATEOUT can be used to lower the scale factor. An external capacitor sets 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 ADXRS624 is available in a 7 mm x 7 mm x 3 mm BGA chip scale package.
APPLICATIONS
Navigation systems Inertial measurement units Platform stabilization Robotics
FUNCTIONAL BLOCK DIAGRAM
+5V (ADC REF) 100nF +5V AVCC 100nF AGND DEMOD
DRIVE AMP
ST2
ST1
TEMP
VRATIO
ADXRS624 ADXRS624
SELF-TEST
25k AT 25C
25k
MECHANICAL SENSOR
AC AMP
VGA
+5V
VDD CHARGE PUMP AND VOLTAGE REGULATOR PGND CP1 CP2 CP3 CP4 CP5 SUMJ 100nF 22nF 22nF COUT
200k 5%
100nF
RATEOUT
08999-001
Figure 1. ADXRS624 Block Diagram
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)2010 Analog Devices, Inc. All rights reserved.
ADXRS624 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 ADXRS624 and Supply Ratiometricity ......................................9 Null Adjustment ......................................................................... 10 Self-Test Function ...................................................................... 10 Continuous Self-Test.................................................................. 10 Outline Dimensions ....................................................................... 11 Ordering Guide .......................................................................... 11 Automotive Products ................................................................. 11
REVISION HISTORY
4/10--Revision 0: Initial Version
Rev. 0 | Page 2 of 12
ADXRS624 SPECIFICATIONS
All minimum and maximum specifications are guaranteed; typical specifications are not guaranteed. At TA = -40C to +105C, VS = AVCC = VDD = 5 V, VRATIO = AVCC, angular rate = 0/s, bandwidth = 80 Hz (COUT = 0.01 F), IOUT = 100 A, 1 g, unless otherwise noted. Table 1.
Parameter SENSITIVITY (RATIOMETRIC) 1 Measurement Range2 Initial and Over Temperature Temperature Drift3 Nonlinearity NULL (RATIOMETRIC)1 Null Linear Acceleration Effect NOISE PERFORMANCE Rate Noise Density FREQUENCY RESPONSE Bandwidth4 Sensor Resonant Frequency SELF-TEST (RATIOMETRIC)1 ST1 Rate-Out Response ST2 Rate-Out Response Logic 1 Input Voltage Logic 0 Input Voltage Input Impedance TEMPERATURE SENSOR (RATIOMETRIC)1 VOUT at 25C Scale Factor5 Load to VS Load to Common TURN-ON TIME OUTPUT DRIVE CAPABILITY Current Drive Capacitive Load Drive POWER SUPPLY Operating Voltage (VS) VRATIO Input Supply Current TEMPERATURE RANGE Specified Performance
1 2 3
Conditions Clockwise rotation is positive output Full-scale range over specifications range
Min 50 22.5
ADXRS624BBGZ Typ Max 75 25 3 0.1 2.5 0.1 0.04
Unit /sec mV//sec % % of FS V /sec/g /sec/Hz
27.5
Best fit straight line -40C to +105C Any axis TA = 25C 1
1000 14.5
Hz kHz V V V V k V mV/C k k ms A pF V V mA C
ST1 pin from Logic 0 to Logic 1 ST2 pin from Logic 0 to Logic 1 0.8 x VRATIO
-1.9 1.9 0.2 x VRATIO
To common Load = 100 M At 25C, VRATIO = 5 V 2.35
50 2.5 9 25 25 2.65
Power on to 1/2/sec of final For rated specifications
50 200 1000 4.75 3 5.00 3.5 -40 5.25 VS 5.0 +105
Parameter is linearly ratiometric with VRATIO. 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 from +25C to +105C. 4 Adjusted by the external capacitor, COUT. 5 For a change in temperature from 25C to 26C. VTEMP is ratiometric to VRATIO. See the Temperature Output and Calibration section for more details.
Rev. 0 | Page 3 of 12
ADXRS624 ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Acceleration (Any Axis, 0.5 ms) Unpowered Powered VDD, AVCC VRATIO Output Short-Circuit Duration (Any Pin to Common) Operating Temperature Range Storage Temperature Rating 2000 g 2000 g -0.3 V to +6.0 V AVCC Indefinite -55C to +125C -65C to +150C
RATE-SENSITIVE AXIS
The ADXRS624 is a Z-axis rate-sensing device (also called a yaw rate-sensing 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
08999-002
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 2000 g and can exceed the absolute maximum rating of the device. Exercise care during handling to avoid damage.
0.25V
Figure 2. RATEOUT Signal Increases with Clockwise Rotation
ESD CAUTION
Rev. 0 | Page 4 of 12
ADXRS624 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
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 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. 0 | Page 5 of 12
08999-003
AGND
RATEOUT
ADXRS624 TYPICAL PERFORMANCE CHARACTERISTICS
N > 1000 for all typical performance plots, unless otherwise noted.
35 30
45 40
PERCENT OF POPULATION (%)
PERCENT OF POPULATION (%)
08999-004
35 30 25 20 15 10 5 0
25 20 15 10 5 0
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.0
3.1
3.2
3.3
3.4
0
2
4
6
-8
-6
-4
-2
8
-10
10
RATEOUT (V)
SENSITIVITY DRIFT (%)
Figure 4. Null Output at 25C (VRATIO = 5 V)
35 30
Figure 7. Sensitivity Drift over Temperature
40 35
PERCENT OF POPULATION (%)
PERCENT OF POPULATION (%)
25 20 15 10 5 0
30 25 20 15 10 5 0
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
-2.10
-2.05
-2.00
-1.95
-1.90
-1.85
-1.80
-1.75
-1.70
-1.65
-1.60
-1.55
-1.50
-1.45
-1.40
-1.35
-1.30
2.10
08999-005
RATEOUT TEMPCO (/sec/C)
ST1 (V)
Figure 5. Null Drift over Temperature (VRATIO = 5 V)
30
40 35
Figure 8. ST1 Output Change at 25C (VRATIO = 5 V)
PERCENT OF POPULATION (%)
25
PERCENT OF POPULATION (%)
30 25 20 15 10 5
20
15
10
5
0
0
24.00
24.25
24.50
24.75
25.00
25.25
25.50
25.75
26.00
26.25
26.50
26.75
27.00
27.25
27.50
1.30
1.35
1.40
1.45
1.50
1.55
1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.05
08999-006
SENSITIVITY (mV//sec)
ST2 (V)
Figure 6. Sensitivity at 25C (VRATIO = 5 V)
Figure 9. ST2 Output Change at 25C (VRATIO = 5 V)
Rev. 0 | Page 6 of 12
08999-009
08999-008
08999-007
ADXRS624
30
40 35
PERCENT OF POPULATION (%)
08999-010
PERCENT OF POPULATION (%)
25
30 25 20 15 10 5
20
15
10
5
50
54
58
62
66
70
74
78
82
86
90
94
MEASUREMENT RANGE (/sec)
98
2.40 2.42 2.44 2.46 2.48 2.50 2.52 2.54 2.56 2.58 2.60 VTEMP OUTPUT (V)
Figure 10. Measurement Range
2.5 2.0 1.5 1.0
Figure 13. VTEMP Output at 25C (VRATIO = 5 V)
3.3 3.1 2.9
VTEMP OUTPUT (V)
SELF-TEST (V)
2.7 2.5 2.3 2.1 1.9 1.7 256 PARTS
0.5 0 -0.5 -1.0 -1.5 -2.0
08999-011
-20
0
20
40
60
80
100
120
-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 REF 50 40 Y X +45 -45 30
PERCENT OF POPULATION (%)
25
20
15
g OR /s
20 10 0
10
5
-10
0
08999-012
2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5
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
08999-015
-20 750
08999-014
-2.5 -40
1.5 -40
08999-013
0
0
ADXRS624
2.0 1.8 1.6
0.05 0.10
LATITUDE LONGITUDE RATE
PEAK RATEOUT (/s)
1.4 1.2
(/s)
08999-016
1.0 0.8 0.6
0
-0.05
0.4 0.2
0 20 40 60 80 100 120 140
08999-019
0 100
-0.10 TIME (Hours)
1k FREQUENCY (Hz)
10k
Figure 16. Typical Response to 10 g Sinusoidal Vibration (Sensor Bandwidth = 2 kHz)
400 300 DUT1 OFFSET BY +200/s 200 100
Figure 19. Typical Shift in 90 sec Null Averages Accumulated over 140 Hours
0.10
0.05
(/s)
0 -100 -200 -300 -400 0 50 100 (ms) 150 200 250 DUT2 OFFSET BY -200/s
(/s)
08999-017
0
-0.05
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
0.01
(/s/ Hz rms)
(/s rms)
0.001
08999-018
0.1
1
10
100
1k
10k
100k
100
1k (Hz)
10k
100k
AVERAGE 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
08999-021
0.001 0.01
0.0001 10
08999-020
-0.10
ADXRS624 THEORY OF OPERATION
The ADXRS624 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 through CP4 can be omitted, and this supply can be connected to CP5 (Pin 6D, Pin 7D). Note that CP5 should not be grounded when power is applied to the ADXRS624. 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 ADXRS624.
0.1 0.01
(/s/ 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 ADXRS624 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 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.
VTEMP VRATIO
08999-023
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 ADXRS624 rate response. The -3 dB frequency set by ROUT and COUT is
fOUT =
(2 x x ROUT x COUT )
1
and can be well controlled because ROUT is trimmed during manufacture to be 200 k 1%. Any external resistor applied between the RATEOUT pin (1B, 2A) and SUMJ pin (1C, 2C) results in
RFIXED
RTEMP
Figure 23. ADXRS624 Temperature Sensor Structure
CALIBRATED PERFORMANCE
Using a three-point calibration technique, it is possible to calibrate the null and sensitivity drift of the ADXRS624 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.
ROUT =
(200 k x REXT ) (200 k + REXT )
In general, an additional hardware or software filter is added to attenuate high frequency noise arising from demodulation spikes at the gyro'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, this additional filter's corner frequency is set to greater than 5x the required bandwidth to preserve good phase response. Figure 22 shows the effect of adding a 250 Hz filter to the output of an ADXRS624 set to 40 Hz bandwidth (as shown in Figure 21). High frequency demodulation artifacts are attenuated by approximately 18 dB.
ADXRS624 AND SUPPLY RATIOMETRICITY
The ADXRS624 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 ADXRS624 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
Rev. 0 | Page 9 of 12
08999-022
0.000001 10
ADXRS624
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 = 4.75 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 ADXRS624 includes a self-test feature that actuates each of the sensing structures and associated electronics as if subjected to angular rate. The self-test feature 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 -1.9 V, and ST2 causes an opposite change of +1.9 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 x VRATIO to the ST1 and ST2 pins. ST1 and ST2 are deactivated by applying a voltage of less than 0.2 x 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 ADXRS624 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 outlining continuous self-test techniques are also available in the AN-768 Application Note.
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
ADXRS624 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, 2 ADXRS624WBBGZ ADXRS624WBBGZ-RL EVAL-ADXRS624Z
1 2
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 BG-32-3 BG-32-3
Z = RoHS Compliant Part. W = Qualified for Automotive Applications.
AUTOMOTIVE PRODUCTS
The ADXRS624WBBGZ models are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. Note that these automotive models may have specifications that differ from the commercial models; therefore, designers should review the Specifications section of this data sheet carefully. Only the automotive grade products shown are available for use in automotive applications. Contact your local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for these models.
Rev. 0 | Page 11 of 12
ADXRS624 NOTES
(c)2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D08999-0-4/10(0)
Rev. 0 | Page 12 of 12

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