Analog Devices ADXSR 401 Service Manual

Page 1

±75°/s Single Chip Yaw Rate

FEATURES

Complete rate gyroscope on a single chip Z-axis (yaw-rate) response High vibration rejection over wide frequency 2000 g powered shock survivability Self-test on digital command Temperature sensor output Precision voltage reference output Absolute rate output for precision applications 5 V single-supply operation Ultra small and light (< 0.15 cc, < 0.5 gram)

APPLICATIONS

GPS navigation systems Image stabilization Inertial measurement units Platform stabilization

FUNCTIONAL BLOCK DIAGRAM

–

100nF 100nF

AVCC

ST1

ST2

SELF TEST

RATE

SENSOR

2G 1F

GENERAL DESCRIPTION

The ADXRS401 is a functionally complete and low cost angular rate sensor (gyroscope), integrated with all of the required electronics on one chip. It is manufactured using Analog Devices’ surface-micromachining technique, the same high volume BIMOS process used for high reliability automotive airbag accelerometers. It is available in a 7 mm × 7 mm × 3 mm BGA surface-mount package.

The output signal, RATEOUT (1B, 2A), is a voltage proportional to angular rate about the axis normal to the top surface of the package (see Figure 2). 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 (see Figure 1).

A precision reference and a temperature output are also provided for compensation techniques. Two digital self-test inputs electromechanically excite the sensor to test proper operation of both sensors and the signal conditioning circuits.

AGND

CORIOLIS SIGNAL CHANNEL

DEMOD

RESONATOR LOOP

≈

Gyro with Signal Conditioning

ADXRS401

OUT

SEN

SUMJ

OUT

180kΩ 1%

RATEOUT

CMID

SEN

9kΩ±35%≈9kΩ±35%

CHARGE PUMP/REG.

CP1

PDD

PGND

100nF

4A 5A 7E 6G

CP2

22nF

ADXRS401

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.

7F 6A 7D7C7B

Figure 1.

2.5V REF

PTAT

12V

CP4

CP3 CP5

1µF

22nF

www.analog.com

2.5V

TEMP

04992-001

Page 2

ADXRS401

TABLE OF CONTENTS

Specifications..................................................................................... 3

Absolute Maximum Ratings............................................................ 4

Rate-Sensitive Axis ....................................................................... 4

Pin Configuration and Function Descriptions............................. 5

Typical Performance Characteristics............................................. 6

Theory of Operation ........................................................................ 8

Supply and Common Considerations ....................................... 8

Setting Bandwidth ........................................................................ 9

Increasing Measurement Range ................................................. 9

Temperature Output and Calibration........................................ 9

Use with a Supply-Ratiometric ADC....................................... 10

Null Adjust................................................................................... 10

Self-Test Function....................................................................... 10

Acceleration Sensitivity ............................................................. 10

Outline Dimensions ....................................................................... 12

Ordering Guide........................................................................... 12

REVISION HISTORY

7/04—Revision 0: Initial Version

Rev. 0 | Page 2 of 12

Page 3

ADXRS401

SPECIFICATIONS

@TA = 25°C, Vs = 5 V, bandwidth = 80 Hz (C

Table 1.

Parameter Conditions Min Typ Max Unit

SENSITIVITY Top view clockwise rotation is positive output

Dynamic Range

Scale Factor

Nonlinearity Best fit straight line 0.1 % of FS

NULL

Initial Null 2.50 V Turn-On Time Power on to ± ½°/s of final 35 ms Linear Acceleration Effect Any axis 0.2 °/s/g

NOISE PERFORMANCE

Rate Noise @ 10 Hz bandwidth 3 mV (rms)

FREQUENCY RESPONSE

3 dB Bandwidth2 (User Selectable) 22 nF as C Sensor Resonant Frequency 14 kHz

SELF TEST

ST1 RATEOUT Response

ST2 RATEOUT Response3 ST2 pin from Logic 0 to 1 +800 mV Logic 1 Input Voltage Standard high logic level definition 3.3 V Logic 0 Input Voltage Standard low logic level definition 1.7 V Input Impedance To common 50

TEMPERATURE SENSOR

at 298K 2.50 V

OUT

Max Current Load on Pin Source to common 50 µA Scale Factor Proportional to absolute temperature 8.4 mV/K

OUTPUT DRIVE CAPABILITY

Output Voltage Swing I Capacitive Load Drive 1000 pF

2.5 V REFERENCE Voltage Value 2.5 V Load Drive to Ground Source 200 µA Load Regulation 0 < I

POWER SUPPLY

Operating Voltage Range 4.75 5.00 5.25 V Quiescent Supply Current 6.0 8.0 mA

TEMPERATURE RANGE

Operating Temperature Range

= 0.01 µF), angular rate = 0°/s, ± 1 g, unless otherwise noted.

OUT

Full-scale range, −40°C to +85°C

−40°C to +85°C

(see Setting Bandwidth section) 40 Hz

OUT

ST1 pin from Logic 0 to 1

= ±100 µA 0.25 VS – 0.25 V

OUT

< 200 µA 5.0 mV/mA

OUT

±75 °/s

12.75 15 17.25 mV/°/s

−40

−800

+85 °C

kΩ

Dynamic range is the maximum full-scale measurement range possible, including output swing range, initial offset, sensitivity, offset drift, and sensitivity drift at 5 V

supplies.

Frequency at which response is 3 dB down from dc response with specified compensation capacitor value. Internal pole forming resistor is 180 kΩ. See the S

Bandwidth

Self-test response varies with temperature. See the section for details. Self-Test Function

section.

etting

Rev. 0 | Page 3 of 12

Page 4

ADXRS401

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

Acceleration (Any Axis, Unpowered, 0.5 ms) 2000 g Acceleration (Any Axis, Powered, 0.5 ms) 2000 g +V

Output Short-Circuit Duration (Any Pin to Common)

Operating Temperature Range

Storage Temperature

−0.3 V to +6.0 V

Indefinite

−55°C to +125°C

−65°C to +150°C

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.

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.

Applications requiring more than 200 cycles to MIL-STD-883 Method 1010 Condition B (–55°C to +125°C) require underfill or other means to achieve this requirement.

Drops onto hard surfaces can cause shocks of greater than 2000 g and exceed the absolute maximum rating of the device. Care should be exercised in handling to avoid damage.

RATE-SENSITIVE AXIS

This Z-axis rate-sensing device is 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 (clockwise when looking down at the package lid).

RATE

AXIS

LONGITUDINAL

AXIS

ABCDEFG

LATERAL AXIS

Figure 2. RATEOUT Signal Increases with Clockwise Rotation

VCC= 5V

GND

RATEOUT

2.5V

4.75V

RATE IN

0.25V

04992-002

Rev. 0 | Page 4 of 12

Page 5

ADXRS401

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

PGND

ST1

ST2

TEMP

PDD

CP5

CP3

CP4

CP1

CP2

AVCC

AGND

GFEDCBA

2.5V

SUMJ

CMID

RATEOUT

Figure 3. BGA-32 (Bottom View)

Table 3. Pin Function Descriptions

Pin No. Mnemonic Description

6D, 7D CP5

HV Filter Capacitor to Ground – 1 µF 20 V minimum

6A, 7B CP4 Charge Pump Capacitor – 22 nF 6C, 7C CP3 Charge Pump Capacitor – 22 nF 5A, 5B CP1 Charge Pump Capacitor – 22 nF 4A, 4B CP2 Charge Pump Capacitor – 22 nF 3A, 3B AVCC + Analog Supply 1B, 2A RATEOUT Rate Signal Output 1C, 2C SUMJ Output Amp Summing Junction 1D, 2D CMID HF Filter Capacitor – 100 nF 1E, 2E V2.5 2.5 V Precision Reference 1F, 2G AGND Analog Supply Return 3F, 3G TEMP Temperature Voltage Output 4F, 4G ST2 Self-Test for Sensor 2 5F, 5G ST1 Self-Test for Sensor 1 6G, 7F PGND Charge Pump Supply Return 6E, 7E PDD + Charge Pump Supply

04992-020

Rev. 0 | Page 5 of 12

Page 6

ADXRS401

TYPICAL PERFORMANCE CHARACTERISTICS

@ BW = 40 Hz, Typical Vibration Characteristics, 10 g Flat Band, 20 Hz to 2 kHz.

% OF POPULATION

1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5 OUTPUT IN VOLTS

Figure 4. Initial Null Output

% OF POPULATION

–10–8–6–4–20246810

NULL SHIFT IN mV/°C

Figure 5. Null Tempco

04992-003

04992-004

% OF POPULATION

–8 –6 –4 –2 0 2 4 86

% SENSITIVITY SHIFT OVER TEMPERATURE

Figure 7. Sensitivity Change Over Temperature

PACKAGE LATERAL AXIS (1/60 SEC SAMPLE RATE)

2.50

2.49

2.48

2.47

RATEOUT (V)

2.46

2.45 05

TIME (Seconds)

Figure 8. 10 g Random Vibration in Package-Lateral Axis Orientation

PACKAGE LONGITUDINAL AXIS (1/60 SEC SAMPLE RATE)

2.50

04992-006

04992-007

% OF POPULATION

13.50 14.00 14.50 15.00 15.50 16.00 16.50 SENSITIVITY IN mV/DEGREE/SECOND

Figure 6. Initial Sensitivity

04992-005

Rev. 0 | Page 6 of 12

2.49

2.48

2.47

RATEOUT (V)

2.46

2.45 05

TIME (Seconds)

04992-008

Figure 9. 10 g Random Vibration in Package-Longitudinal Axis Orientation

Page 7

ADXRS401

2.50

RATE AXIS (1/60 SEC SAMPLE RATE)

2.50

PACKAGE LONGITUDINAL AXIS (0.5s AVERAGE)

2.49

2.48

2.47

RATEOUT (V)

2.46

2.45 05

TIME (Seconds)

Figure 10. 10 g Random Vibration in Rate Axis Orientation

PACKAGE LATERAL AXIS (0.5s AVERAGE)

10g

RATEOUT (V)

2.50

2.49

2.48

2.47

2.46

04992-009

Figure 12. 10 g Random Vibration in Package-Longitudinal Axis Orientation

2.49

2.48

2.47

RATEOUT (V)

2.46

2.45 05

2.50

2.49

2.48

2.47

RATEOUT (V)

2.46

10g

TIME (Seconds)

RATE AXIS (0.5s AVERAGE)

10g

04992-011

2.45 05

TIME (Seconds)

Figure 11. 10 g Random Vibration in Package-Lateral Axis Orientation

04992-010

2.45 05

TIME (Seconds)

04992-012

Figure 13. 10 g Random Vibration in Rate Axis Orientation

Rev. 0 | Page 7 of 12

Page 8

ADXRS401

THEORY OF OPERATION

22nF

100nF

PGND

CP1

22nF

CP2

AVCC

RATEOUT

CP4

SUMJ

= 22nF

OUT

Figure 14. Example Application Circuit (Top View)

Note that inner rows/columns of pins have been omitted for clarity but should be connected in the application.

The ADXRS401 operates on the principle of a resonator gyro. Two polysilicon sensing structures each contain a dither frame, which is electrostatically driven to resonance. This produces 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 dualsensor 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 14 V to 16 V for operation. Since only 5 V is typically available in most applications, a charge pump is included on-chip. If an external 14 V to 16 V supply is available, the two capacitors on CP1 to CP4 can be omitted and this supply can be connected to CP5 (Pin 7D) with a 1 µF decoupling capacitor.

After the demodulation stage there is a single-pole low-pass filter consisting of an internal 9 kΩ resistor (R

) and an

SEN1

external user-supplied capacitor (CMID). A CMID capacitor of 100 nF sets a 400 Hz low-pass pole ± 35% and is used to limit high frequency artifacts before final amplification. A bandwidth limit capacitor, C

, sets the pass bandwidth (see Setting

OUT

Bandwidth section).

1µF

PDD

2.5V

PGND

AGND

CP4

ST1

ST2

TEMP

04992-013

CP5

CP3

7D 7E

100nF

CMID

100nF

SUPPLY AND COMMON CONSIDERATIONS

Only power supplies used for supplying analog circuits are recommended for powering the ADXRS401. High frequency noise and transients associated with digital circuit supplies may have adverse affects on device operation. 1 µF shows the recommended connections for the ADXRS401 where both AVCC and PDD have a separate decoupling capacitor. These should be placed as close to their respective pins as possible before routing to the system analog supply. This will minimize the noise injected by the charge pump that uses the PDD supply.

It is also recommended to place the charge pump capacitors connected to the CP1 to CP4 pins as close to the part as possible. These capacitors are used to produce the on-chip high voltage supply switched at the dither frequency at approximately 14 kHz. Care should be taken to ensure that there is no more than 50 pF of stray capacitance between CP1 to CP4 and ground. Surface-mount chip capacitors are suitable as long as they are rated for over 15 V.

Rev. 0 | Page 8 of 12

Page 9

ADXRS401

(

)

SETTING BANDWIDTH

External capacitors CMID and C with on-chip resistors to create two low-pass filters to limit the bandwidth of the ADXRS401’s rate response. The –3 dB frequency set by R

OUT

and C

are used in combination

OUT

is:

OUT

INCREASING MEASUREMENT RANGE

To increase the full-scale measurement range of the ADXRS401, place an external resistor between the RATEOUT (1B, 2A) and SUMJ (1C, 2C) pins. This parallels the internal R is factory-trimmed to 180 kΩ.

resistor that

OUT

CRπ21/f ×××=

OUTOUTOUT

This frequency can be well controlled since R

has been

OUT

trimmed during manufacturing to be 180 kΩ ±1%. Any external resistor applied between the RATEOUT (1B, 2A) and SUMJ (1C, 2C) pins will result in:

OUT

()(

+×=

RkΩ180/RkΩ180

)

EXTEXT

The −3 dB frequency is set by RSEN (the parallel combination

and R

of R

SEN1

controlled, because R

) at about 4.5 kΩ nominal. CMID is less well

SEN2

SEN1

and R

have been used to trim the

SEN2

rate sensitivity during manufacturing and have a ±35% tolerance. Its primary purpose is to limit the high frequency demodulation artifacts from saturating the final amplifier stage. Thus, this pole of nominally 400 Hz @ 0.1 µF need not be precise. Lower frequency is preferable, but its variability usually requires it to be about 10 times greater (in order to preserve phase integrity) than the well-controlled output pole. In general, both −3 dB filter frequencies should be set as low as possible to reduce the amplitude of these high frequency artifacts, as well as to reduce the overall system noise.

–

100nF

AVCC

ST1

ST2

SELF TEST

RATE

SENSOR

2G 1F

CORIOLIS SIGNAL CHANNEL

RESONATOR LOOP

AGND

DEMOD

For example, a 330 kΩ external resistor gives approximately 10mV/°/sec sensitivity and a commensurate ∼50% increase in the full-scale range. This is effective for up to a 4× increase in the full-scale range. (The minimum value of the parallel resistor allowed is 45 kΩ.) Beyond this amount of external sensitivity reduction, the internal circuitry headroom requirements prevent further increase in the linear full-scale output range.

The drawbacks of modifying the full-scale range are the additional output null drift (as much as 2°/sec over temperature) and the readjustment of the initial null bias. See Null Adjust section and Application Note AN-625 for details.

TEMPERATURE OUTPUT AND CALIBRATION

It is common practice to temperature-calibrate gyros to improve their overall accuracy. The ADXRS401 has a temperature-proportional voltage output that provides input to such a calibration method. The voltage at TEMP (3F, 3G) is nominally 2.5 V at 27°C and has a PTAT (proportional to absolute temperature) characteristic of 8.4 mV/°C. Note that the TEMP output circuitry is limited to 50 µA source current.

Limiting the bandwidth of the device reduces the flat-band noise during the calibration process, improving the measurement accuracy at each calibration point.

SUMJ

OUT

180kΩ 1%

OUT

RATEOUT

100nF

CMID

SEN

≈

9kΩ±35%≈9kΩ±35%

SEN

ADXRS401

CHARGE PUMP/REG.

4A 5A 7E 6G

CP2

22nF

PDD

CP1

7F 6A 7D7C7B

PGND CP4

100nF

2.5V REF

PTAT

12V

CP3 CP5

1µF

22nF

2.5V

TEMP

04992-014

Figure 15. Block Diagram with External Components

Rev. 0 | Page 9 of 12

Page 10

ADXRS401

USE WITH A SUPPLY-RATIOMETRIC ADC

The ADXRS401’s RATEOUT signal is nonratiometric (that is, neither the null voltage nor the rate sensitivity is proportional to the supply). Rather, they are nominally constant for dc supply changes within the 4.75 V to 5.25 V operating range. If the ADXRS401 is used with a supply-ratiometric ADC, the ADXRS401’s 2.5 V output can be converted and used to make corrections in software for the supply variations.

NULL ADJUST

Null adjustment is possible by injecting a suitable current to SUMJ (1C, 2C). Simply add a suitable resistor to either the ground or the positive supply. The nominal 2.5 V null is for a symmetrical swing range at RATEOUT (1B, 2A). In some applications, a nonsymmetrical output swing may be suitable. If a resistor is connected to the positive supply, supply disturbances may reflect some null instability. Avoid digital supply noise, particularly in this case (see the Supply and Common Considerations section).

The resistor value to use is approximately:

×=

is the unadjusted zero rate output, and V

NULL0

null value. If the initial value is below the desired value, the resistor should terminate on common or ground. If it is above the desired value, the resistor should terminate on the 5 V supply. Values typically are in the 1 MΩ to 5 MΩ range.

If an external resistor is used across RATEOUT and SUMJ, the parallel equivalent value is substituted into the above equation. Note that the resistor value is an estimate since it assumes

= 5.0 V and V

SUMJ

= 2.5 V.

SELF-TEST FUNCTION

The ADXRS401 includes a self-test feature that stimulates 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 inputs ST1 (5F, 5G), ST2 (4F, 4G), or both. ST1 causes the voltage at RATEOUT to change about −0.800 V, and ST2 causes an opposite +0.800 V.

Activating both ST1 and ST2 simultaneously is not damaging. Because ST1 and ST2 are not necessarily closely matched, actuating both simultaneously may result in an apparent null bias shift.

)V – V180,000)/( (2.5 R

NULL1NULL0NULL

is the target

NULL1

ACCELERATION SENSITIVITY

The sign convention used is that lateral acceleration is positive in the direction from Pin Column A to Pin Column G of the package. That is, a device has positive sensitivity if its voltage output increases when the row of Pins 2A to 6A are tipped under the row 2G to 6G in the Earth’s gravity.

There are two effects of concern: shifts in the static null and induced null noise. Scale factor is not significantly affected until acceleration reaches several hundred meters per second squared.

Vibration rectification for frequencies up to 20 kHz is of the order of 0.00002(°/s)/(m/s

0.0003(°/s)/(m/s

2)2

the lid. It is not significantly dependent on frequency, and has been verified up to 300 m/s

Linear vibration spectral density near the 14 kHz sensor resonance translates into output noise. In order to have a significant effect, the vibration must be within the angular rate bandwidth (typically ±40 Hz of the resonance), so it takes considerable high frequency vibration to have any effect.

Away from the 14 kHz resonance, the effect is not discernible, except for vibration frequencies within the angular rate pass band. The in-band effect can be seen in Figure 17. This is the result of the static g-sensitivity. The specimen used for Figure 17 had a g-sensitivity of 0.15 °/s/g and its total in-band noise degraded from 3 mV rms to 5 mV rms for the specified vibration. The effect of broadband vibration up is shown in Figure 18 and Figure 19.

The output noise of the part falls away in accordance with the output low-pass filter and does not contain any spikes greater than 1% of the low frequency noise. A typical noise spectrum is shown in Figure 16.

–60

–70

–80

–90

–100

RATEOUT (V)

–110

2)2

in the primary axis and

for acceleration applied along a diagonal of

rms.

–120

–130

0 10 100 1k 10k 100k

Figure 16. Noise Spectral Density at RATEOUT – BW = 4Hz

FREQUENCY (Hz)

04992-015

Rev. 0 | Page 10 of 12

Page 11

ADXRS401

2.60

2.58

2.56

2.54

RATEOUT (V)

2.52

2.50 02468

TIME (Seconds)

Figure 17. Random Vibration (Lateral) 2 Hz to 40 Hz 3.2 g rms

2.60

2.58

2.56

2.54

RATEOUT (V)

2.52

04992-016

2.58

2.56

2.54

RATEOUT (V)

2.52

2.50 02468

STATIC 0.8mV rms

SHAKING 2.5mV rms

TIME (Seconds)

Figure 19. Random Vibration (Lateral) 10 kHz to 20 kHz

√

at 0.01 g/

0.07

0.06

0.05

0.04

0.03

0.02

Hz with 60 Hz Sampling and 0.5 Sec Averaging

04992-018

0.01

0 10 100

TIME (Seconds)

Figure 20. Root Allen Variance vs. Averaging Time

04992-019

2.50 02468

TIME (Seconds)

Figure 18. Random Vibration (Lateral) 10 kHz to 20 kHz

at 0.01 g/

√

Hz with 60 Hz Sampling and 0.5 Sec Averaging

04992-017

Rev. 0 | Page 11 of 12

Page 12

ADXRS401

OUTLINE DIMENSIONS

3.20

2.50

3.65 MAX

7.00 BSC SQ

BALL A1 INDICATOR

TOP VIEW

DETAIL A

0.80 BSC

0.44

0.25

76543

4.80 BSC

DETAIL A

0.60

0.55

0.50

BALL DIAMETER

Figure 21. 32-Lead Chip Scale Ball Grid Array [CSPBGA]

(BC-32)

Dimensions shown in millimeters

A1 CORNER

INDEX AREA

SEATING PLANE

A B C D E F G

0.15 MAX COPLANARITY

ORDERING GUIDE

Model Temperature Range Package Description Package Outline

ADXRS401ABG

ADXRS401ABG-REEL

−40°C to +85°C

ADXRS401EB Evaluation Board

32-Lead BGA BC-32

C04992–0–7/04(0)

Rev. 0 | Page 12 of 12