ADXL321JCP [ADI]
Small and Thin 18 g Accelerometer; 小而薄18克加速度计
| 型号： | ADXL321JCP |
| 厂家： | 
ADI |
| 描述： | Small and Thin 18 g Accelerometer |
| 文件： | 总16页 (文件大小：390K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Small and Thin ± ±1
g
Accelerometer
ADXL32±
FEATURES
GENERAL DESCRIPTION
Small and thin
4 mm × 4 mm × 1.45 mm LFCSP package
3 mg resolution at 50 Hz
Wide supply voltage range: 2.4 V to 6 V
Low power: 350 µA at VS = 2.4 V (typ)
Good zero g bias stability
The ADXL321 is a small and thin, low power, complete dual-
axis accelerometer with signal conditioned voltage outputs,
which is all on a single monolithic IC. The product measures
acceleration with a full-scale range of 1ꢀ g (typical). It can also
measure both dynamic acceleration (vibration) and static
acceleration (gravity).
Good sensitivity accuracy
The ADXL321’s typical noise floor is 320 µg/√Hz, allowing
signals below 3 mg to be resolved in tilt-sensing applications
using narrow bandwidths (<50 Hz).
X-axis and Y-axis aligned to within 0.1° (typ)
BW adjustment with a single capacitor
Single-supply operation
10,000 g shock survival
Compatible with Sn/Pb and Pb-free solder processes
The user selects the bandwidth of the accelerometer using
capacitors CX and CY at the XOUT and YOUT pins. Bandwidths of
0.5 Hz to 2.5 kHz may be selected to suit the application.
APPLICATIONS
The ADXL321 is available in a very thin 4 mm × 4 mm ×
1.45 mm, 16-lead, plastic LFCSP.
Vibration monitoring and compensation
Abuse event detection
Sports equipment
FUNCTIONAL BLOCK DIAGRAM
+3V
V
S
ADXL321
C
AC
AMP
OUTPUT
AMP
OUTPUT
AMP
DC
DEMOD
SENSOR
R
R
FILT
32kΩ
FILT
32kΩ
COM
ST
Y
C
X
OUT
OUT
C
X
Y
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
Fax: 781.326.8703
www.analog.com
© 2004 Analog Devices, Inc. All rights reserved.
ADXL32±
TABLE OF CONTENTS
Specifications..................................................................................... 3
Setting the Bandwidth Using CX and CY ................................. 12
Self-Test ....................................................................................... 12
Absolute Maximum Ratings............................................................ 4
ESD Caution.................................................................................. 4
Pin Configuration and Function Descriptions............................. 5
Typical Performance Characteristics (VS = 3.0 V) ....................... 7
Theory of Operation ...................................................................... 11
Performance ................................................................................ 11
Applications..................................................................................... 12
Power Supply Decoupling ......................................................... 12
Design Trade-Offs for Selecting Filter Characteristics: The
Noise/BW Trade-Off.................................................................. 12
Use with Operating Voltages Other than 3 V............................. 13
Use as a Dual-Axis Tilt Sensor ................................................. 13
Outline Dimensions....................................................................... 14
Ordering Guide .......................................................................... 14
REVISION HISTORY
12/04—Revision 0: Initial Version
Rev. 0 | Page 2 of 16
ADXL32±
SPECIFICATIONS±
TA = 25°C, VS = 3 V, CX = CY = 0.1 µF, Acceleration = 0 g, unless otherwise noted.
Table 1.
Parameter
Conditions
Min
Typ
Max
Unit
SENSOR INPUT
Each axis
Measurement Range
Nonlinearity
Package Alignment Error
Alignment Error
Cross Axis Sensitivity
SENSITIVITY (RATIOMETRIC)2
Sensitivity at XOUT, YOUT
Sensitivity Change due to Temperature3
ZERO g BIAS LEVEL (RATIOMETRIC)
0 g Voltage at XOUT, YOUT
0 g Offset vs. Temperature
NOISE PERFORMANCE
Noise Density
1ꢀ
0.2
1
0.1
2
g
%
% of full scale
Degrees
Degrees
%
X sensor to Y sensor
Each axis
VS = 3 V
VS = 3 V
Each axis
VS = 3 V
51
57
0.01
63
mV/g
%/°C
1.4
1.5
2
1.6
V
mg/°C
@ 25°C
320
µg/√Hz rms
FREQUENCY RESPONSE4
CX, CY Range5
0.002
10
µF
RFILT Tolerance
Sensor Resonant Frequency
SELF-TEST6
32 15%
5.5
kΩ
kHz
Logic Input Low
Logic Input High
0.6
2.4
50
V
V
kΩ
mV
ST Input Resistance to Ground
Output Change at XOUT, YOUT
OUTPUT AMPLIFIER
Output Swing Low
Output Swing High
POWER SUPPLY
Self-test 0 to 1
1ꢀ
No load
No load
0.3
2.6
V
V
Operating Voltage Range
Quiescent Supply Current
Turn-On Time7
2.4
6
V
mA
ms
0.49
20
TEMPERATURE
Operating Temperature Range
−20
+70
°C
1 All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed.
2 Sensitivity is essentially ratiometric to VS.
3 Defined as the change from ambient-to-maximum temperature or ambient-to-minimum temperature.
4 Actual frequency response controlled by user-supplied external capacitor (CX, CY).
5 Bandwidth = 1/(2 × π × 32 kΩ × C). For CX, CY = 0.002 µF, bandwidth = 2500 Hz. For CX, CY = 10 µF, bandwidth = 0.5 Hz. Minimum/maximum values are not tested.
6 Self-test response changes cubically with VS.
7 Larger values of CX, CY increase turn-on time. Turn-on time is approximately 160 × CX or CY + 4 ms, where CX, CY are in µF.
Rev. 0 | Page 3 of 16
ADXL32±
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Rating
Stresses above those listed under 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.
Acceleration (Any Axis, Unpowered)
Acceleration (Any Axis, Powered)
VS
10,000 g
10,000 g
−0.3 V to +7.0 V
(COM − 0.3 V) to
(VS + 0.3 V)
All Other Pins
Output Short-Circuit Duration
(Any Pin to Common)
Operating Temperature Range
Storage Temperature
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.
Rev. 0 | Page 4 of 16
ADXL32±
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
NC
16
V
V
NC
13
S
S
15
14
NC
ST
X
OUT
1
2
3
4
12
11
10
9
NC
Y
ADXL321
TOP VIEW
(Not to Scale)
COM
NC
OUT
NC
5
6
7
8
COM COM COM NC
NC = NO CONNECT
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
Pin No.
Mnemonic
Description
Do Not Connect
Self-Test
1, 4, ꢀ, 9, 11, 13, 16
2
NC
ST
3, 5 to 7
10
12
COM
YOUT
XOUT
VS
Common
Y Channel Output
X Channel Output
2.4 V to 6 V
14, 15
Rev. 0 | Page 5 of 16
ADXL32±
CRITICAL ZONE
TO T
tP
T
L
P
T
P
RAMP-UP
T
L
tL
T
SMAX
T
SMIN
tS
RAMP-DOWN
PREHEAT
t
25°C TO PEAK
TIME
Figure 3. Recommended Soldering Profile
Table 4. Recommended Soldering Profile
Profile Feature
Sn63/Pb37
Pb-Free
Average Ramp Rate (TL to TP)
Preheat
3°C/s max
3°C/s max
Minimum Temperature (TSMIN
)
100°C
150°C
Minimum Temperature (TSMAX
Time (TSMIN to TSMAX), tS
TSMAX to TL
)
150°C
60 s − 120 s
200°C
60 s − 150 s
Ramp-Up Rate
3°C/s
3°C/s
Time Maintained Above Liquidous (TL)
Liquidous Temperature (TL)
Time (tL)
Peak Temperature (TP)
Time within 5°C of Actual Peak Temperature (tP)
Ramp-Down Rate
1ꢀ3°C
60 s − 150 s
240°C + 0°C/−5°C
10 s − 30 s
6°C/s max
217°C
60 s − 150 s
260°C + 0°C/−5°C
20 s − 40 s
6°C/s max
ꢀ min max
Time 25°C to Peak Temperature
6 min max
Rev. 0 | Page 6 of 16
ADXL32±
TYPICAL PERFORMANCE CHARACTERISTICS (VS = 3.0 V)
25
20
15
10
5
25
20
15
10
5
0
0
1.40 1.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58 1.60
VOLTS
1.40 1.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58 1.60
VOLTS
Figure 4. X-Axis Zero g Bias at 25°C
Figure 7. Y-Axis Zero g Bias at 25°C
25
20
15
10
5
25
20
15
10
5
0
0
–10 –8
–6
–4
–2
0
2
4
6
8
10
–10 –8
–6
–4
–2
0
2
4
6
8
10
mg/°C
mg/°C
Figure 5. X-Axis Zero g Bias Temperature Coefficient
Figure 8. Y-Axis Zero g Bias Temperature Coefficient
50
45
40
35
30
25
20
15
10
5
50
45
40
35
30
25
20
15
10
5
0
0
52
53
54
55
56
57
58
59
60
52
53
54
55
56
57
58
59
60
mV/
g
mV/g
Figure 6. X-Axis Sensitivity at 25°C
Figure 9. Y-Axis Sensitivity at 25°C
Rev. 0 | Page 7 of 16
ADXL32±
1.600
1.575
1.550
1.525
1.500
1.475
1.450
1.425
1.400
0.060
0.059
0.058
0.057
0.056
0.055
0.054
0.053
0.052
–30 –20 –10
0
10
20
30
40
50
60
70
80
–30
–10
10
30
50
70
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 10. Zero g Bias vs. Temperature—Parts Soldered to PCB
Figure 13. Sensitivity vs. Temperature—Parts Soldered to PCB
30
30
25
20
15
10
5
25
20
15
10
5
0
0
200
220
240
260
280
300
320
340
200
220
240
260
280
300
320
340
NOISE DENSITY (µg/ Hz)
NOISE DENSITY (µg/ Hz)
Figure 11. X-Axis Noise Density at 25°C
Figure 14. Y-Axis Noise Density at 25°C
25
20
15
10
5
30
25
20
15
10
5
0
0
–5
–4
–3
–2
–1
0
1
2
3
4
5
–5
–4
–3
–2
–1
0
1
2
3
4
5
PERCENT SENSITIVITY (%)
PERCENT SENSITIVITY (%)
Figure 12. Z vs. X Cross-Axis Sensitivity
Figure 15. Z vs. Y Cross-Axis Sensitivity
Rev. 0 | Page ꢀ of 16
ADXL32±
16
14
12
10
8
6
4
2
0
10
11 12
13 14
15 16
mV
17 18
19 20
21
Figure 19. Turn-On Time—CX, CY = 0.1 µF, Time Scale = 2 ms/DIV
Figure 16. X-Axis Self-Test Response at 25°C
40
35
30
25
20
15
10
5
0
420 430 440 450 460 470 480 490 500 510 520 530
CURRENT ( A)
µ
Figure 17. Supply Current at 25°C
16
14
12
10
8
6
4
2
0
10
11 12
13 14
15 16
mV
17 18
19 20
21
Figure 18. Y-Axis Self-Test Response at 25°C
Rev. 0 | Page 9 of 16
ADXL32±
XL
X
Y
= 1.443V
= 1.500V
OUT
OUT
321J
#1234
5678P
X
Y
= 1.500V
= 1.443V
X
Y
= 1.500V
= 1.557V
OUT
OUT
OUT
OUT
5 6 7 8 P
X
= 1.557V
= 1.50V
# 1 2 3 4
OUT
OUT
3 2 1 J
Y
X L
X
Y
= 1.500V
= 1.500V
OUT
OUT
EARTH'S SURFACE
Figure 20. Output Response vs. Orientation (Top View)
Rev. 0 | Page 10 of 16
ADXL32±
THEORY OF OPERATION
The ADXL321 is a complete acceleration measurement system
on a single monolithic IC. The ADXL321 has a measurement
range of 1ꢀ g. It contains a polysilicon surface-micromachined
sensor and signal conditioning circuitry to implement an open-
loop acceleration measurement architecture. The output signals
are analog voltages that are proportional to acceleration. The
accelerometer measures static acceleration forces, such as
gravity, which allows it to be used as a tilt sensor.
The demodulator’s output is amplified and brought off-chip
through a 32 kΩ resistor. The user then sets the signal
bandwidth of the device by adding a capacitor. This filtering
improves measurement resolution and helps prevent aliasing.
PERFORMANCE
Rather than using additional temperature compensation
circuitry, innovative design techniques have been used to ensure
high performance is built-in. As a result, there is neither
quantization error nor nonmonotonic behavior, and
temperature hysteresis is very low (typically less than 10 mg
over the −20°C to +70°C temperature range).
The sensor is a polysilicon surface-micromachined structure
built on top of a silicon wafer. Polysilicon springs suspend the
structure over the surface of the wafer and provide a resistance
against acceleration forces. Deflection of the structure is
measured using a differential capacitor that consists of
independent fixed plates and plates attached to the moving
mass. The fixed plates are driven by 1ꢀ0° out-of-phase square
waves. Acceleration deflects the beam and unbalances the
differential capacitor, resulting in an output square wave whose
amplitude is proportional to acceleration. Phase-sensitive
demodulation techniques are then used to rectify the signal and
determine the direction of the acceleration.
Figure 10 shows the zero g output performance of eight parts
(X- and Y-axis) over a −20°C to +70°C temperature range.
Figure 13 demonstrates the typical sensitivity shift over
temperature for supply voltages of 3 V. This is typically better
than 1ꢁ over the −20°C to +70°C temperature range.
Rev. 0 | Page 11 of 16
ADXL32±
APPLICATIONS
POWER SUPPLY DECOUPLING
DESIGN TRADE-OFFS FOR SELECTING FILTER
CHARACTERISTICS: THE NOISE/BW TRADE-OFF
For most applications, a single 0.1 µF capacitor, CDC, adequately
decouples the accelerometer from noise on the power supply.
However, in some cases, particularly where noise is present at
the 140 kHz internal clock frequency (or any harmonic
thereof), noise on the supply may cause interference on the
ADXL321 output. If additional decoupling is needed, a 100 Ω
(or smaller) resistor or ferrite bead may be inserted in the
supply line. Additionally, a larger bulk bypass capacitor (in the
The accelerometer bandwidth selected ultimately determines
the measurement resolution (smallest detectable acceleration).
Filtering can be used to lower the noise floor, which improves
the resolution of the accelerometer. Resolution is dependent on
the analog filter bandwidth at XOUT and YOUT
.
The output of the ADXL321 has a typical bandwidth of 2.5 kHz.
The user must filter the signal at this point to limit aliasing
errors. The analog bandwidth must be no more than half the
A/D sampling frequency to minimize aliasing. The analog
bandwidth may be further decreased to reduce noise and
improve resolution.
1 µF to 4.7 µF range) may be added in parallel to CDC
.
SETTING THE BANDWIDTH USING CX AND CY
The ADXL321 has provisions for band-limiting the XOUT and
YOUT pins. Capacitors must be added at these pins to implement
low-pass filtering for antialiasing and noise reduction. The
equation for the 3 dB bandwidth is
The ADXL321 noise has the characteristics of white Gaussian
noise, which contributes equally at all frequencies and is
described in terms of µg/√Hz (the noise is proportional to the
square root of the accelerometer’s bandwidth). The user should
limit bandwidth to the lowest frequency needed by the
application in order to maximize the resolution and dynamic
range of the accelerometer.
F
−3 dB = 1/(2π(32 kΩ) × C(X, Y)
or more simply,
–3 dB = 5 µF/C(X, Y)
)
F
The tolerance of the internal resistor (RFILT) typically varies as
much as 15ꢁ of its nominal value (32 kΩ), and the bandwidth
varies accordingly. A minimum capacitance of 2000 pF for CX
and CY is required in all cases.
With the single-pole, roll-off characteristic, the typical noise of
the ADXL321 is determined by
rmsNoise = (320 µg/ Hz)×( BW×1.6)
At 100 Hz bandwidth the noise will be
Table 5. Filter Capacitor Selection, CX and CY
Bandwidth (Hz)
Capacitor (µF)
1
10
50
100
200
500
4.7
rmsNoise = (320µg/ Hz)×( 100×1.6) = 4mg
0.47
0.10
0.05
0.027
0.01
Often, the peak value of the noise is desired. Peak-to-peak noise
can only be estimated by statistical methods. A factor of 6 is
generally used to convert rms to peak-to-peak. Table 6 is useful
for estimating the probabilities of exceeding various peak
values, given the rms value.
SELF-TEST
Table 6. Estimation of Peak-to-Peak Noise
The ST pin controls the self-test feature. When this pin is set to
VS, an electrostatic force is exerted on the accelerometer beam.
The resulting movement of the beam allows the user to test if
the accelerometer is functional. The typical change in output is
315 mg (corresponding to 1ꢀ mV). This pin may be left open-
circuit or connected to common (COM) in normal use.
% of Time That Noise Exceeds
Nominal Peak-to-Peak Value
Peak-to-Peak Value
2 × rms
4 × rms
6 × rms
ꢀ × rms
32
4.6
0.27
0.006
The ST pin should never be exposed to voltages greater than
VS + 0.3 V. If this cannot be guaranteed due to the system design
(for instance, if there are multiple supply voltages), then a low
VF clamping diode between ST and VS is recommended.
Rev. 0 | Page 12 of 16
ADXL32±
Peak-to-peak noise values give the best estimate of the
uncertainty in a single measurement. Table 7 gives the typical
noise output of the ADXL321 for various CX and CY values.
USE AS A DUAL-AXIS TILT SENSOR
An accelerometer is most sensitive to tilt when its sensitive axis
is perpendicular to the force of gravity (that is, when it is
parallel to the earth’s surface). At this orientation, its sensitivity
to changes in tilt is highest. When the accelerometer is oriented
on axis to gravity (near its +1 g or −1 g reading), the change in
output acceleration per degree of tilt is negligible. When the
accelerometer is perpendicular to gravity, its output changes
nearly 17.5 mg per degree of tilt. At 45°, its output changes at
only 12.2 mg per degree of tilt, and resolution declines.
Table 7. Filter Capacitor Selection (CX, CY)
Peak-to-Peak
Noise Estimate
(mg)
Bandwidth
(Hz)
CX, CY
(µF)
RMS Noise
(mg)
10
50
100
500
0.47
0.1
0.047
0.01
1.3
2.9
4
7.ꢀ
17.4
24
9.1
54.6
Converting Acceleration to Tilt
When the accelerometer is oriented so both its X-axis and
Y-axis are parallel to the earth’s surface, it can be used as a 2-axis
tilt sensor with both a roll axis and pitch axis. Once the output
signal from the accelerometer has been converted to an
acceleration that varies between −1 g and +1 g, the output tilt in
degrees is calculated as
USE WITH OPERATING VOLTAGES OTHER THAN 3 V
The ADXL321 is tested and specified at VS = 3 V; however, it can
be powered with VS as low as 2.4 V or as high as 6 V. Note that
some performance parameters change as the supply voltage is
varied.
The ADXL321 output is ratiometric, so the sensitivity (or scale
factor) varies proportionally to supply voltage. At VS = 5 V, the
sensitivity is typically 100 mV/g. At VS = 2.4 V, the sensitivity is
typically 45 mV/g.
PITCH = arcsine(AX/1 g)
ROLL = arcsine(AY/1 g)
Be sure to account for overranges. It is possible for the
accelerometers to output a signal greater than 1 g due to
vibration, shock, or other accelerations.
The zero g bias output is also ratiometric, so the zero g output is
nominally equal to VS/2 at all supply voltages.
The output noise is not ratiometric but is absolute in volts;
therefore, the noise density decreases as the supply voltage
increases. This is because the scale factor (mV/g) increases
while the noise voltage remains constant. At VS = 5 V, the noise
density is typically 190 µg/√Hz, while at VS = 2.4 V, the noise
density is typically 400 µg/√Hz,
Self-test response in g is roughly proportional to the square of
the supply voltage. However, when ratiometricity of sensitivity is
factored in with supply voltage, the self-test response in volts is
roughly proportional to the cube of the supply voltage. For
example, at VS = 5 V, the self-test response for the ADXL321 is
approximately ꢀ0 mV. At VS = 2.4 V, the self-test response is
approximately ꢀ mV.
The supply current decreases as the supply voltage decreases.
Typical current consumption at VS = 5 V is 750 µA, and typical
current consumption at VS = 2.4 V is 350 µA.
Rev. 0 | Page 13 of 16
ADXL32±
OUTLINE DIMENSIONS
0.20 MIN
13
16
PIN 1
INDICATOR
0.20 MIN
0.65 BSC
PIN 1
INDICATOR
1
4
12
9
4.15
4.00 SQ
3.85
2.43
1.75 SQ
1.08
TOP
VIEW
BOTTOM
VIEW
8
5
0.55
0.50
0.45
1.95 BSC
0.05 MAX
0.02 NOM
1.50
1.45
1.40
0.35
0.30
0.25
COPLANARITY
0.05
SEATING
PLANE
Figure 21. 16-Lead Lead Frame Chip Scale Package [MQ_LFCSP]
4 mm × 4 mm Body, Thick Quad (CP-16-5)
Dimensions shown in millimeters
(Drawing Not to Scale)
ORDERING GUIDE
Measurement
Range
Specified
Voltage (V)
Temperature
Range
Package
Option
Model
Package Description
16-Lead LFCSP
16-Lead LFCSP
ADXL321JCP1
ADXL321JCP–REEL1
ADXL321EB
1ꢀ g
1ꢀ g
3
3
−20°C to +70°C
−20°C to +70°C
CP-16-5
CP-16-5
Evaluation Board
1 Lead finish—Matte tin.
Rev. 0 | Page 14 of 16
ADXL32±
NOTES
Rev. 0 | Page 15 of 16
ADXL32±
NOTES
©
2004 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D05291–0–12/04(0)
Rev. 0 | Page 16 of 16
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