High Temperature, Vibration Rejecting
±2000°/sec Gyroscope
Data Sheet
ADXRS645
FEATURES
Innovative ceramic vertical mount package can be oriented
for pitch or roll rate response
Wide temperature range: −40°C to +175°C
Long life: guaranteed 1000 hours at TA = 175°C
High vibration rejection over wide frequency
10,000 g powered shock survivability
Ratiometric to referenced supply
5 V single-supply operation
Self-test on digital command
Temperature sensor output
APPLICATIONS
Down hole measurements for geological exploration
Extreme high temperature industrial applications
Severe mechanical environments
GENERAL DESCRIPTION
The ADXRS645 is a high performance angular rate sensor
with excellent vibration immunity for use in high temperature
environments. The ADXRS645 is manufactured using the
Analog Devices, Inc., patented high volume BiMOS surface-
micromachining process with years of proven field reliability.
An advanced, differential, quad sensor design provides superior
acceleration and vibration rejection.
The output signal, RATEOUT, is a voltage proportional to the
angular rate about the axis normal to the package lid. The
measurement range is a minimum of ±2000°/sec, and may be
extended to ±5000°/sec with the addition of a single external
resistor. 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 ADXRS645 is available in a 8 mm ×
9 mm × 3 mm, 15-lead brazed lead tri in-line package.
FUNCTIONAL BLOCK DIAGRAM
Figure 1.
V
DD
AGND
PGND
AV
CC
ST2 ST1 TEMP V
RATIO
CP1 CP2 CP3 CP4 CP5 SUMJ RATEOUT
DEMOD
180kΩ ±1%
22nF 100nF
22nF
100nF
100nF
100nF
DRIVE
AMP
CHARGE P UM P
AND VOLT AGE
REGULATOR
C
OUT
5V
5V
5V
(ADC REF)
AC
AMP
VGA
25kΩ
@ 25°C
ADXRS645
25kΩ
SELF-TEST
MECHANICAL
SENSOR
11958-001
Rev. A Document Feedback
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Technical Support www.analog.com
ADXRS645 Data Sheet
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
Supply Ratiometricity ...................................................................9
Range Extension ............................................................................9
Self-Test Function .........................................................................9
Continuous Self-Test .....................................................................9
Outline Dimensions ....................................................................... 10
Ordering Guide .......................................................................... 10
REVISION HISTORY
9/14—Rev. 0 to Rev. A
Changes to Features Section............................................................ 1
Added Usable Life Expectancy Parameter, Table 1 ...................... 3
7/14—Revision 0: Initial Version
Rev. A | Page 2 of 10
Data Sheet ADXRS645
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), and IOUT = 100 µA, unless otherwise noted.
Table 1.
Parameter Test Conditions/Comments Min Typ Max Unit
SENSITIVITY
1
Clockwise rotation is positive output
Measurement Range2, 3 ±2000 °/sec
Initial TA = 25°C 1 mV/°/sec
Temperature Drift Uncompensated, −40°C to +150°C4 ±5 %
Uncompensated, 150°C to 175°C −35 %
Nonlinearity
Best fit straight line
0.1
% of FS
NULL1
Initial TA = 25°C 2.4 2.5 2.6 V
Temperature Drift Uncompensated, −40°C to +150°C4 ±50 °/sec
Uncompensated, 150°C to 175°C ±150 °/sec
Linear Acceleration Effect Any axis 0.1 °/sec/g
Vibration Rectification 25 g rms, 50 Hz to 5 kHz 0.0006 °/sec/g2
NOISE PERFORMANCE
Rate Noise Density TA ≤ 25°C 0.25 °/sec/√Hz
Resolution Floor TA = 25°C, 1 minute to 1 hour in-run 100 °/hr
TA = 150°C, 1 minute to 1 hour in-run 150 °/hr
FREQUENCY RESPONSE
Bandwidth (±3 dB)5 No external filter 2000 Hz
Sensor Resonant Frequency 15.5 17.5 20 kHz
SELF-TEST1
ST1 RATEOUT Response ST1 pin from Logic 0 to Logic 1 −1300 °/sec
ST2 RATEOUT Response ST2 pin from Logic 0 to Logic 1 1300 °/sec
ST1 to ST2 Mismatch
6
±2
%
Logic 1 Input Voltage 3.3 V
Logic 0 Input Voltage 1.7 V
Input Impedance To common 40 50 100 kΩ
TEMPERATURE SENSOR1
VTEMP at 25°C Load = 10 MΩ 2.3 2.4 2.5 V
Scale Factor7 25°C, VRATIO = 5 V 9 mV/°C
TURN-ON TIME8 Power on to ±2°/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) 4.75 5.00 5.25 V
Quiescent Supply Current 3.5 mA
TEMPERATURE RANGE
Specified Performance −40 +175 °C
LIFESPAN
Usable Life Expectancy
T
A
= 175°C
1000
Hours
1 Parameter is linearly ratiometric with VRATIO.
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 Measurement range can be extended to as much as ±5000°/s by adding a single 120 kΩ resistor between the RATEOUT and SUMJ pins.
4 Maximum deviation from +25°C to −40°C or +25°C to +150°C, see the Typical Performance Characteristics section for typical behavior over temperature.
5 Adjusted by the 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.
8 Based on characterization.
Rev. A | Page 3 of 10
ADXRS645 Data Sheet
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
Acceleration (Any Axis, 0.5 ms)
Unpowered
10,000
g
Powered 10,000 g
VDD, AVCC −0.3 V to +6.6 V
VRATIO AVCC
ST1, ST2 AVCC
Output Short-Circuit Duration (Any Pin to
Common)
Indefinite
Operating Temperature Range −55°C to +175°C
Storage Temperature Range −65°C to +185°C
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
Drops onto hard surfaces can cause shocks of greater than
10,000 g and can exceed the absolute maximum rating of the
device. Exercise care in handling to avoid damage.
RATE SENSITIVE AXIS
The ADXRS645 produces a positive output voltage for clockwise
rotation about the axis normal to the package lid, that is,
clockwise when looking at the package lid.
Figure 2. RATEOUT Signal Increases with Clockwise Rotation
ESD CAUTION
+
Z-AXIS
RATE
AXIS
11958-002
Rev. A | Page 4 of 10
Data Sheet ADXRS645
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Figure 3. Pin Configuration (Top View)
Figure 4. Pin Configuration (3D View)
Table 3. Pin Function Descriptions
Pin Number Mnemonic Description
A1 CP3 Charge Pump Capacitor, 22 nF
A2 CP5 HV Filter Capacitor, 100 nF
A3 ST1 Positive Self-Test
B1 CP4 Charge Pump Capacitor, 22 nF
B2 VDD Positive Charge Pump Supply
B3 ST2 Negative Self-Test
C1 CP1 Charge Pump Capacitor, 22 nF
C2 PGND Charge Pump Supply Return
C3 TEMP Temperature Voltage Output
D1 CP2 Charge Pump Capacitor, 22 nF
D2 RATEOUT Rate Signal Output
E1 AVCC Positive Analog Supply
E2 SUMJ Output Amplifier Summing Junction
F1
AGND
Analog Supply Return
F2 VRATIO Reference Supply for Ratiometric Output
ADXRS645
TOP VIEW
(No t t o Scal e)
1
CP3
CP4
CP1
CP2
AVCC
AGND
CP5
VDD
PGND
RATEOUT
SUMJ
VRATIO
2 A B C D E F
A B C D E F
3 A B C
ST1 ST2 TEMP
11958-003
11958-200
Rev. A | Page 5 of 10
ADXRS645 Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 5. Null Output at 25°C
Figure 6. Sensitivity at 25°C
Figure 7. ST1 Output Change at 25°C (VRATIO = 5 V)
Figure 8. Null Output Over Temperature
Figure 9. Sensitivity Over Temperature
Figure 10. ST1 Output Over Temperature
50
40
30
20
10
0
PERCENTAGE OF POPULATION (%)
NULL OUTPUT (mV )
2450
2465
2480
2495
2510
2525
2540
2555
2570
2585
2600
11958-104
50
40
30
20
10
45
35
25
15
5
0
PERCENTAGE OF POPULATION (%)
SENSITIVIT Y (mV/°/sec)
0.88
0.91
0.94
0.97
1.00
1.03
1.06
1.09
1.12
1.15
1.18
11958-105
35
30
20
10
25
15
5
0
PERCENTAGE OF POPULATION (%)
ST 1 O UTPUT CHANG E ( °/ sec)
–1600
–1550
–1500
–1450
–1400
–1350
–1300
–1250
–1200
–1150
–1100
11958-106
NULL OUTPUT (mV )
TEMPERATURE (°C)
2400
2450
2500
2550
2600
2650
2700
–50 050 100 150 200
11958-107
SENSITIVIT Y (mV/°/sec)
TEMPERATURE (°C)
0
0.2
0.4
0.6
0.8
1.0
1.2
–50 050 100 150 200
11958-108
ST 1 O UTPUT (°/ sec)
TEMPERATURE (°C)
–2000
0
–200
–400
–600
–800
–1000
–1200
–1400
–1600
–1800
–50 050 100 150 200
11958-109
Rev. A | Page 6 of 10
Data Sheet ADXRS645
Figure 11. ST2 Output Change at 25°C (VRATIO = 5 V)
Figure 12. Self-Test Mismatch at 25°C (VRATIO = 5 V)
Figure 13. VTEMP Output at 25°C
Figure 14. ST2 Output Over Temperature
Figure 15. Allan Variance at 25°C vs. Averaging Time
Figure 16. VTEMP Output Over Temperature
40
35
30
25
20
15
10
5
0
PERCENTAGE OF POPULATION (%)
ST 2 O UTPUT CHANG E ( °/ sec)
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
11958-110
45
40
35
30
25
20
15
10
5
0
PERCENTAGE OF POPULATION (%)
SELF-T EST MI SMATCH (%)
–2.0
–1.5
–1.0
–0.5
0
0.5
1.0
1.5
2.0
2.5
3.0
11958-111
40
35
30
25
20
15
10
5
0
PERCENTAGE OF POPULATION (%)
VTEMP OUTPUT (V)
2.38
2.40
2.42
2.44
2.46
2.48
2.50
2.52
2.54
2.56
2.58
11958-112
ST 2 O UTPUT (°/ sec)
TEMPERATURE (°C)
0
2000
1800
1600
1400
1200
1000
800
600
400
200
–50 050 100 150 200
11958-113
ALLAN VARI ANCE ( °/ Hou r)
AVERAGING TIME (Seconds)
1
10000
1000
100
10
0.01 0.1 110 100 1000 10000
+1σ
AVERAGE
–1σ
11958-114
V
TEMP
OUTPUT (V)
TEMPERATURE (°C)
1.5
4.0
3.5
3.0
2.5
2.0
–50 050 100 150 200
11958-115
Rev. A | Page 7 of 10
ADXRS645 Data Sheet
Figure 17. Current Consumption at 25°C (VRATIO = 5 V)
Figure 18. Typical Noise Spectral Density (COUT = 0.01 µF)
Figure 19. Typical Rate and Phase Response vs. Frequency (COUT = 470 pF
with a Series RC Low-Pass Filter of 3.3 kΩ and 22 nF)
Figure 20. Typical Output Nonlinearity
35
0
5
10
15
20
25
30
PERCENTAGE OF POPULATION (%)
CURRENT CO NS UM P TI ON (mA)
3150
3250
3350
3450
3550
3650
3750
3850
3950
4050
4150
11958-116
NOISE SPECTRAL DENSITY (°/sec/√Hz)
FRE Q UE NCY ( Hz )
0.001
1
0.1
0.01
0.1 110 100 1k 10k
11958-117
0.1 110
–18
–15
–12
–9
–6
–3
0
–180
–150
–120
–90
–60
–30
0
RATE RESPONSE (dB)
PHASE ( Degrees)
FRE Q UE NCY ( kHz )
11958-018
0.06
0.05
0.04
0.03
0.02
0.01
0
0.01
0.02
0.03
0.04
0
–1000 1000 2000
–2000
NONLINEARITY (%FS)
RATE ( °/ sec)
11958-019
Rev. A | Page 8 of 10
Data Sheet ADXRS645
THEORY OF OPERATION
The ADXRS645 operates on the principle of a resonator gyroscope.
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 15 V for operation. Because
only 5 V is typically available in most applications, a charge
pump is included on chip. If an external 17 V to 22 V supply is
available, the two capacitors on CP1 to CP4 can be omitted, and
this supply can be connected to CP5 (Pin A2) through a 1 kΩ
series resistor. Do not ground CP5 when power is applied to the
ADXRS645. 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 ADXRS645.
SETTING BANDWIDTH
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 ADXRS645 rate response. The −3 dB
frequency set by ROUT and COUT is
fOUT = 1/(2 ×
π
× ROUT × COUT)
This frequency can be well controlled because ROUT has been
trimmed during manufacturing to be 180 kΩ ± 1%. Any external
resistor applied between the RATEOUT pin (D2) and SUMJ pin
(E2) results in 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
gyroscope. An RC output filter consisting of a 3.3 kΩ series
resistor and 22 nF shunt capacitor (2.2 kHz pole) is recommended.
TEMPERATURE OUTPUT AND CALIBRATION
It is common practice to temperature calibrate gyroscopes to
improve their overall accuracy. The ADXRS645 has a temperature
proportional voltage output that provides input to such a calibration
method. The temperature sensor structure is shown in Figure 21.
The voltage at TEMP (Pin C3) is nominally 2.4 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.
Figure 21. Temperature Sensor Structure
SUPPLY RATIOMETRICITY
The RATEOUT, ST1, ST2, and TEMP signals of the ADXRS645
are ratiometric to the VRATIO voltage, that is, the null voltage, rate
sensitivity, and temperature outputs are proportional to VRATIO.
Therefore, it is most easily used with a supply ratiometric analog-
to-digital converter (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 must not be greater than AVCC.
RANGE EXTENSION
The ADXRS645 scale factor can be reduced to extend the
measurement range to as much as ±5000°/sec by adding a single
120 kΩ resistor between the RATEOUT and SUMJ pins. If an
external resistor is added between the RATEOUT and SUMJ
pins, proportionally increase COUT to maintain correct
bandwidth (that is, if adding a 180 kΩ resistor, double COUT).
SELF-TEST FUNCTION
The ADXRS645 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 ST1 (Pin A3), ST2 (Pin B3), or both.
ST1 causes the voltage at RATEOUT to change about −1.3 V,
and ST2 causes an opposite change of +1.3 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 (±1%), 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 ADXRS645 gives it higher reliability
than is obtainable with any other high volume manufacturing
method. In addition, 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.
V
RATIO
V
TEMP
R
FIXED
R
TEMP
11958-010
Rev. A | Page 9 of 10
ADXRS645 Data Sheet
OUTLINE DIMENSIONS
Figure 22. 15-Lead Brazed Lead Tri In-line Package [BL_TIP]
(DY-15-1)
Dimensions shown in millimeters
ORDERING GUIDE
Model1 Temperature Range Package Description Package Option
ADXRS645HDYZ −40°C to +175°C 15-Lead Brazed Lead Tri In-line Package [BL_TIP] DY-15-1
1 Z = RoHS Compliant Part.
01-07-2014-A
8.20
8.00
7.80
9.20
9.00
8.80
PKG-004255
BACK VIE W
SIDE VIEW
FRONT VIEW
TOP VIEW
6.30
6.00
5.70
1.30
BSC0.625
BSC2.00
BSC
3.00
BSC
5.00
BSC
1.48
1.35
1.22
3.30
2.85
2.40
0.30
0.25
0.20
2.83
2.70
2.57
0.55
0.50
0.45
©2014 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D11958-0-9/14(A)
Rev. A | Page 10 of 10
