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
APPLICATIONS
Industrial applications
Severe mechanical environments
Platform stabilization
High Stability, Low Noise
GENERAL DESCRIPTION
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.
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
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.
Figure 1.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Page 2
ADXRS646 Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed.
= 25°C, VS = AVCC = VDD = 6 V, V
T
A
otherwise noted.
Table 1.
Parameter Test Conditions/Comments Min Typ Max Unit
SENSITIVITY1 Clockwise rotation is positive output
Measurement Range2 Full-scale range over specifications range ±250 ±300 °/sec
Initial
Temperature Drift3 ±3 %
Nonlinearity Best fit straight line 0.01 % of FS
NULL1
Null −40°C to +105°C 2.7 3.0 3.3 V
Calibrated Null4 −40°C to +105°C ±0.1 °/sec
Temperature Drift3 ±3 °/sec
Linear Acceleration Effect Any axis 0.015 °/sec/g
Vibration Rectification 25 g rms, 50 Hz to 5 kHz 0.0001 °/sec/g2
NOISE PERFORMANCE
Rate Noise Density TA ≤ 25°C 0.01 °/sec/√Hz
Rate Noise Density TA ≤ 105°C 0.015 °/sec/√Hz
Resolution Floor
FREQUENCY RESPONSE
5
Sensor Resonant Frequency 15.5 17.5 20 kHz
SELF-TEST1
ST1 RATEOUT Response
ST2 RATEOUT Response ST2 pin from Logic 0 to Logic 1 50 °/sec
ST1 to ST2 Mismatch6 −5
Logic 1 Input Voltage ST1 pin or ST2 pin 4 V
Logic 0 Input Voltage 2 V
Load to Common 25 kΩ
TURN-ON TIME4 Power on to ±0.5°/sec of final with CP5 = 100 nF 50 ms
OUTPUT DRIVE CAPABILITY
Current Drive For rated specifications 200 µA
Capacitive Load Drive 1000 pF
POWER SUPPLY
Operating Voltage (VS) 5.75 6.00 6.25 V
Quiescent Supply Current 4 mA
TEMPERATURE RANGE
1
Parameter is linearly ratiometric with V
2
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 +25°C to −40°C or +25°C to +105°C.
4
Based on characterization.
5
Adjusted by external capacitor, C
6
Self-test mismatch is described as (ST2 + ST1)/((ST2 − ST1)/2).
.
RATIO
. Reducing bandwidth below 0.01 Hz does not result in further noise improvement.
OUT
Rev. 0 | Page 3 of 12
Page 4
ADXRS646 Data Sheet
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
Acceleration (Any Axis, 0.5 ms)
Unpowered 10,000 g
Powered 10,000 g
VDD, AV
CC
V
AVCC
RATIO
−0.3 V to +6.6 V
ST1, ST2 AVCC
Output Short-Circuit Duration
Indefinite
(Any Pin to Common)
Operating Temperature Range −55°C to +125°C
Storage Temperature Range −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.
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.
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
LONGITUDINAL
AXIS
ABCDG
A1
EF
LATERAL AXIS
Figure 2. RATEOUT Signal Increases with Clockwise Rotation
N > 1000 for all typical performance plots, unless otherwise noted.
Figure 4. Null Bias at 25°C
Figure 7. Sensitivity at 25°C
Figure 5. Null Drift over Temperature (V
Figure 6. Null Output over Temperature, 16 Parts in Sockets (V
= 5 V)
RATIO
RATIO
= 5 V)
Figure 9. Typical Root Allan Deviation at 25°C vs. Averaging Time
Figure 8. Sensitivity Drift over Temperature
Rev. 0 | Page 6 of 12
Page 7
Data Sheet ADXRS646
25
0
5
10
15
20
PERCENT OF POPULATION (%)
ST1Δ (mV)
–650
–630
–610
–590
–570
–550
–530
–510
–490
–470
–450
–430
–410
–390
–370
–350
09771-006
–0.30
–0.35
–0.40
–0.45
–0.50
–0.55
–0.60
–0.65
–0.70
–0.75
ST1Δ (V)
TEMPERATURE (°C)
–60 –40 –20020406080 100 120 140
09771-104
70
60
50
40
30
20
10
0
PERCENT OF POPULATION (%)
MISMATCH ( %)
–4–3–2–101234
09771-008
25
0
5
10
15
20
PERCENT OF POPULATION (%)
ST2Δ (mV)
350
370
390
410
430
450
470
490
510
530
550
570
590
610
630
650
09771-007
0.75
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
ST2Δ (V)
TEMPERATURE (°C)
–60 –40 –20020406080 100 120 140
09771-103
9
–18
–15
–12
–9
–6
–3
0
3
6
0
–90
–80
–70
–60
–50
–40
–30
–20
–10
MAGNITUDE RESPONSE (dB)
PHASE RESPO NS E ( Degrees)
FREQUENCY ( kHz )
0.1110
09771-101
C
OUT
= 470pF
MAGNITUDE
PHASE
Figure 10. ST1 Output Change at 25°C (V
RATIO
= 5 V)
Figure 11. ST1 Output Change vs. Temperature, 16 Parts in Sockets
Figure 13. ST2 Output Change at 25°C (V
RATIO
= 5 V)
Figure 14. ST2 Output Change vs. Temperature, 16 Parts in Sockets
Figure 12. Self-Test Mismatch at 25°C (V
RATIO
= 5 V)
Figure 15. ADXRS646 Frequency Response with a 2.2 kHz Output Filter
Rev. 0 | Page 7 of 12
Page 8
ADXRS646 Data Sheet
80
70
60
50
40
30
20
10
0
PERCENT OF POPULATION (%)
V
TEMP
OUTPUT (V)
2.70
2.75
2.80
2.85
2.90
2.95
3.00
3.05
3.10
3.15
3.20
3.25
3.30
09771-009
4.5
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
V
TEMP
(V)
TEMPERATURE (°C)
–100–50050100150
09771-102
35
30
25
20
15
10
5
0
PERCENT OF POPULATION (%)
CURRENT CONSUMP TION (mA)
2.82.93.03.13.23.33.4
09771-013
Figure 16. V
Figure 17. V
Output at 25°C (V
TEMP
Output vs. Temperature
TEMP
RATIO
= 5 V)
Figure 18. Current Consumption at 25°C (V
RATIO
= 5 V)
Rev. 0 | Page 8 of 12
Page 9
Data Sheet ADXRS646
X
Y
Z
09771-015
V
RATIO
V
TEMP
R
FIXEDRTEMP
09771-016
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.
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.
SETTING BANDWIDTH
The combination of an external capacitor (C
on-chip resistor (R
) creates a low-pass filter that limits the
OUT
bandwidth of the ADXRS646 rate response. The −3 dB
frequency set by R
= 1/(2 × π × R
f
OUT
and can be well controlled because R
OUT
and C
OUT
OUT
× C
is
OUT
)
OUT
manufacturing to 180 kΩ ± 1%. Any external resistor applied
between the RATEOUT pin (1B, 2A) and SUMJ pin (1C, 2C)
results in
R
= (180 kΩ × R
OUT
)/(180 kΩ + R
EXT
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.
) and the
OUT
is trimmed during
)
EXT
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.
The voltage at TEMP (3F, 3G) is nominally 2.9 V at 25°C, and
V
= 6 V. T he temperature coefficient is 10 mV/°C (typical)
RAT IO
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.
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. 0 | Page 9 of 12
Figure 20. Temperature Sensor Structure
Page 10
ADXRS646 Data Sheet
SUPPLY RATIOMETRICITY
The null output voltage (RATEOUT), sensitivity, self-test
responses (ST1 and ST2), and temperature output (TEMP)
of the ADXRS646 are ratiometric to V
. Therefore, using
RAT IO
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, V
should not be greater than AVCC.
RAT IO
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.
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 AV
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.
. The self-test response
CC
CONTINUOUS SELF-TEST
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.
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. Details outlining continuous self-test techniques
are available in the AN-768 Application Note, Using the ADXRS150/ADXRS300 in Continuous Self-Te st Mo d e. Although
the title of this application note refers to other Analog Devices
gyroscopes, the techniques apply equally to the ADXRS646.
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,
C
must be proportionally increased to maintain correct
OUT
bandwidth.
Rev. 0 | Page 10 of 12
Page 11
Data Sheet ADXRS646
1
0.1
0.01
0.001
0.0001
0.00001
(°/sec)
2
/ Hz
FREQUENCY ( Hz )
101001k10k
09771-017
WITH VIBRATION
NO VIBRATION
0.12
–0.04
–0.02
0
0.02
0.04
0.06
0.08
0.10
(°/sec)
FREQUENCY ( Hz )
101001k10k
09771-018
IMMUNITY TO VIBRATION
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.
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.
Figure 22. ADXRS646 Sine Vibration Output Response (5 g, 20 Hz to 5 kHz);
Gyroscope Bandwidth Set to 1600 Hz
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. 0 | Page 11 of 12
Page 12
ADXRS646 Data Sheet
3
OUTLINE DIMENSIONS
A1 BALL
CORNER
7.05
6.85 SQ
6.70
4.80
BSC SQ
0.80
BSC
76543
21
*
A
B
C
D
E
F
G
A1 CORNER
INDEX AREA
.80 MAX
TOP VIEW
DETAIL A
0.60 MAX
0.25 MIN
SEATING
PLANE
*
BALL A1 IDENTIFIER IS GOLD PLATED AND CONNECTED
TO THE D/A PAD INTERNALLY VIA HOLES.
BOTTOM VIEW
DETAIL A
0.60
0.55
0.50
BALL DIAMETER
3.20 MAX
2.50 MIN
COPLANARITY
0.15
10-26-2009-B
Figure 23. 32-Lead Ceramic Ball Grid Array [CBGA]
(BG-32-3)
Dimensions shown in millimeters
ORDERING GUIDE
Model1 Temperature Range Package Description Package Option