Small, Low Power, 3-Axis ±5 g
Accelerometer
ADXL325
FEATURES
GENERAL DESCRIPTION
3-axis sensing
Small, low profile package
4 mm × 4 mm × 1.45 mm LFCSP
Low power: 350 μA typical
Single-supply operation: 1.8 V to 3.6 V
10,000 g shock survival
Excellent temperature stability
Bandwidth adjustment with a single capacitor per axis
RoHS/WEEE lead-free compliant
The ADXL325 is a small, low power, complete 3-axis accelerometer
with signal conditioned voltage outputs. The product measures
acceleration with a minimum full-scale range of ±5 g. It can
measure the static acceleration of gravity in tilt-sensing applications,
as well as dynamic acceleration, resulting from motion, shock,
or vibration.
The user selects the bandwidth of the accelerometer using
the CX, CY, and CZ capacitors at the XOUT, YOUT, and ZOUT pins.
Bandwidths can be selected to suit the application with a range
of 0.5 Hz to 1600 Hz for X and Y axes and a range of 0.5 Hz to
550 Hz for the Z axis.
APPLICATIONS
The ADXL325 is available in a small, low profile, 4 mm ×
4 mm × 1.45 mm, 16-lead, plastic lead frame chip scale package
(LFCSP_LQ).
Cost-sensitive, low power, motion- and tilt-sensing applications
Mobile devices
Gaming systems
Disk drive protection
Image stabilization
Sports and health devices
FUNCTIONAL BLOCK DIAGRAM
+3V
VS
ADXL325
OUTPUT AMP
XOUT
CX
3-AXIS
SENSOR
CDC
~32kΩ
AC AMP
DEMOD
OUTPUT AMP
~32kΩ
YOUT
CY
OUTPUT AMP
~32kΩ
ZOUT
CZ
ST
07946-001
COM
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
www.analog.com
Fax: 781.461.3113
©2009 Analog Devices, Inc. All rights reserved.
ADXL325
TABLE OF CONTENTS
Features .............................................................................................. 1
Performance ................................................................................ 10
Applications ....................................................................................... 1
Applications Information .............................................................. 11
General Description ......................................................................... 1
Power Supply Decoupling ......................................................... 11
Functional Block Diagram .............................................................. 1
Setting the Bandwidth Using CX, CY, and CZ .......................... 11
Revision History ............................................................................... 2
Self Test ........................................................................................ 11
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 4
Design Trade-Offs for Selecting Filter Characteristics: The
Noise/BW Trade-Off .................................................................. 11
ESD Caution .................................................................................. 4
Use with Operating Voltages Other Than 3 V .......................... 11
Pin Configuration and Function Descriptions ............................. 5
Axes of Acceleration Sensitivity ............................................... 12
Typical Performance Characteristics ............................................. 6
Layout and Design Recommendations ................................... 13
Theory of Operation ...................................................................... 10
Outline Dimensions ....................................................................... 14
Mechanical Sensor...................................................................... 10
Ordering Guide .......................................................................... 14
REVISION HISTORY
8/09—Revision 0: Initial Version
Rev. 0 | Page 2 of 16
ADXL325
SPECIFICATIONS
TA = 25°C, VS = 3 V, CX = CY = CZ = 0.1 μF, acceleration = 0 g, unless otherwise noted. All minimum and maximum specifications are
guaranteed. Typical specifications are not guaranteed.
Table 1.
Parameter
SENSOR INPUT
Measurement Range
Nonlinearity
Package Alignment Error
Interaxis Alignment Error
Cross-Axis Sensitivity 1
SENSITIVITY (RATIOMETRIC) 2
Sensitivity at XOUT, YOUT, ZOUT
Sensitivity Change Due to Temperature 3
ZERO g BIAS LEVEL (RATIOMETRIC)
0 g Voltage at XOUT, YOUT, ZOUT
0 g Offset vs. Temperature
NOISE PERFORMANCE
Noise Density XOUT, YOUT, ZOUT
FREQUENCY RESPONSE 4
Bandwidth XOUT, YOUT 5
Bandwidth ZOUT5
RFILT Tolerance
Sensor Resonant Frequency
SELF TEST 6
Logic Input Low
Logic Input High
ST Actuation Current
Output Change at XOUT
Output Change at YOUT
Output Change at ZOUT
OUTPUT AMPLIFIER
Output Swing Low
Output Swing High
POWER SUPPLY
Operating Voltage Range
Supply Current
Turn-On Time 7
TEMPERATURE
Operating Temperature Range
Conditions
Each axis
Min
Typ
±5
±6
±0.2
±1
±0.1
±1
Each axis
VS = 3 V
VS = 3 V
156
174
±0.01
192
mV/g
%/°C
VS = 3 V
1.3
1.5
±1
1.7
V
mg/°C
Percent of full scale
No external filter
No external filter
Self test 0 to 1
Self test 0 to 1
Self test 0 to 1
−90
+90
+90
No load
No load
Max
g
%
Degrees
Degrees
%
250
μg/√Hz rms
1600
550
32 ± 15%
5.5
Hz
Hz
kΩ
kHz
+0.6
+2.4
+60
−190
+190
+320
V
V
μA
mV
mV
mV
−350
+350
+580
0.1
2.8
1.8
VS = 3 V
No external filter
1
V
V
3.6
V
μA
ms
+85
°C
350
1
−40
Unit
Defined as coupling between any two axes.
Sensitivity is essentially ratiometric to VS.
3
Defined as the output change from ambient-to-maximum temperature or ambient-to-minimum temperature.
4
Actual frequency response controlled by user-supplied external filter capacitors (CX, CY, CZ).
5
Bandwidth with external capacitors = 1/(2 × π × 32 kΩ × C). For CX, CY = 0.003 μF, bandwidth = 1.6 kHz. For CZ = 0.01 μF, bandwidth = 500 Hz. For CX, CY, CZ = 10 μF,
bandwidth = 0.5 Hz.
6
Self test response changes cubically with VS.
7
Turn-on time is dependent on CX, CY, CZ and is approximately 160 × CX or CY or CZ + 1 ms, where CX, CY, CZ are in μF.
2
Rev. 0 | Page 3 of 16
ADXL325
ABSOLUTE MAXIMUM RATINGS
Rating
10,000 g
10,000 g
−0.3 V to +3.6 V
(COM − 0.3 V) to (VS + 0.3 V)
Indefinite
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.
−55°C to +125°C
−65°C to +150°C
ESD CAUTION
Table 2.
Parameter
Acceleration (Any Axis, Unpowered)
Acceleration (Any Axis, Powered)
VS
All Other Pins
Output Short-Circuit Duration
(Any Pin to Common)
Temperature Range (Powered)
Temperature Range (Storage)
Rev. 0 | Page 4 of 16
ADXL325
ST
2
NC
15
14
13
ADXL325
TOP VIEW
(Not to Scale)
12
XOUT
11
NC
10
YOUT
+Y
+Z
+X
5
6
7
8
ZOUT
9
COM
NC
4
COM
3
COM
COM
NC
NC = NO CONNECT
07946-003
1
VS
16
NC
VS
NC
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
EP
Mnemonic
NC
ST
COM
NC
COM
COM
COM
ZOUT
NC
YOUT
NC
XOUT
NC
VS
VS
NC
Exposed pad
Description
No Connect (or Optionally Ground)
Self Test
Common
No Connect
Common
Common
Common
Z Channel Output
No Connect (or Optionally Ground)
Y Channel Output
No Connect
X Channel Output
No Connect
Supply Voltage (1.8 V to 3.6 V)
Supply Voltage (1.8 V to 3.6 V)
No Connect
Not internally connected. Solder for mechanical integrity.
Rev. 0 | Page 5 of 16
ADXL325
TYPICAL PERFORMANCE CHARACTERISTICS
N > 1000 for all typical performance plots, unless otherwise noted.
50
60
50
POPULATION (%)
30
20
10
40
30
20
10
1.46
1.47
1.48
1.49
1.5
1.51
1.52
1.53
1.54
OUTPUT (V)
0
07946-005
0
–0.22
–0.20
–0.18
–0.16
–0.14
–0.12
VOLTAGE (V)
Figure 3. X-Axis Zero g Bias at 25°C, VS = 3 V
07946-008
POPULATION (%)
40
Figure 6. X-Axis Self Test Response at 25°C, VS = 3 V
40
60
50
POPULATION (%)
POPULATION (%)
30
20
40
30
20
10
1.46
1.47
1.48
1.49
1.50
1.51
1.52
1.53
1.54
OUTPUT (V)
0
07946-006
VOLTAGE (V)
Figure 7. Y-Axis Self Test Response at 25°C, VS = 3 V
60
25
50
20
40
POPULATION (%)
30
15
10
5
30
20
10
1.46
1.47
1.48
1.49
1.50
1.51
1.52
1.53
OUTPUT (V)
1.54
0
07946-007
POPULATION (%)
Figure 4. Y-Axis Zero g Bias at 25°C, VS = 3 V
0
0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22
0.26 0.27 0.28 0.29 0.30 0.31 0.32 0.33 0.34 0.35 0.36
VOLTAGE (V)
Figure 5. Z-Axis Zero g Bias at 25°C, VS = 3 V
Figure 8. Z-Axis Self Test Response at 25°C, VS = 3 V
Rev. 0 | Page 6 of 16
07946-010
0
07946-009
10
ADXL325
50
1.55
45
1.54
40
1.53
35
1.52
30
1.51
20
1.50
1.49
15
1.48
10
1.47
5
1.46
0
–1.4
–1.0
–0.6
–0.2
0.2
0.6
1.0
1.4
TEMPERATURE COEFFICIENT (mg/°C)
1.45
–40 –30 –20 –10
Figure 9. X-Axis Zero g Bias Temperature Coefficient, VS = 3 V
0
10
20
30
40
50
60
70
80
90 100
TEMPERATURE (°C)
07946-014
OUTPUT (V)
25
07946-011
POPULATION (%)
N=8
Figure 12. X-Axis Zero g Bias vs. Temperature, Eight Parts Soldered to PCB
50
1.55
N=8
1.54
1.53
1.52
30
OUTPUT (V)
POPULATION (%)
40
20
1.51
1.50
1.49
1.48
10
1.47
–1.4
–1.0
–0.6
–0.2
0.2
0.6
1.0
1.4
TEMPERATURE COEFFICIENT (mg/°C)
1.45
–40 –30 –20 –10
07946-012
0
Figure 10. Y-Axis Zero g Bias Temperature Coefficient, VS = 3 V
0
10
20
30
40
50
60
70
80
90 100
TEMPERATURE (°C)
07946-015
1.46
Figure 13. Y-Axis Zero g Bias vs. Temperature, Eight Parts Soldered to PCB
40
1.54
N=8
35
1.52
1.50
OUTPUT (V)
25
20
15
1.46
–3.5 –3.0 –2.5 –2.0 –1.5 –1.0 –0.5
0
0.5 1.0 1.5 2.0 2.5
TEMPERATURE COEFFICIENT (mg/°C)
Figure 11. Z-Axis Zero g Bias Temperature Coefficient, VS = 3 V
1.40
–40 –30 –20 –10
0
10
20
30
40
50
TEMPERATURE (°C)
60
70
80
90 100
07946-016
1.42
5
0
1.48
1.44
10
07946-013
POPULATION (%)
30
Figure 14. Z-Axis Zero g Bias vs. Temperature, Eight Parts Soldered to PCB
Rev. 0 | Page 7 of 16
ADXL325
30
N=8
0.187
25
SENSITIVITY (V/g)
15
10
0.177
0.172
0.167
5
0.157
–40 –30 –20 –10
0.164
0.166
0.168
0.170
0.172
0.174
0.176
0.178
0.180
0.182
SENSITIVITY (V/g)
07946-017
0
10
20
30
40
50
60
70
80
90 100
90 100
TEMPERATURE (°C)
Figure 15. X-Axis Sensitivity at 25°C, VS = 3 V
Figure 18. X-Axis Sensitivity vs. Temperature,
Eight Parts Soldered to PCB, VS = 3 V
40
N=8
35
0.187
30
0.182
SENSITIVITY (V/g)
POPULATION (%)
0
07946-020
0.162
07946-021
POPULATION (%)
0.182
20
25
20
15
0.177
0.172
0.167
10
0.162
5
0.164
0.166
0.168
0.170
0.172
0.174
0.176
0.178
0.180
0.182
SENSITIVITY (V/g)
0.157
–40 –30 –20 –10
07946-018
0
0
10
20
30
40
50
60
70
80
TEMPERATURE (°C)
Figure 16. Y-Axis Sensitivity at 25°C, VS = 3 V
Figure 19. Y-Axis Sensitivity vs. Temperature,
Eight Parts Soldered to PCB, VS = 3 V
0.187
35
N=8
30
0.182
SENSITIVITY (V/g)
20
15
0.177
0.172
0.167
10
0
0.164
0.166
0.168
0.170
0.172
0.174
0.176
0.178
0.180
SENSITIVITY (V/g)
0.182
0.157
–40 –30 –20 –10
0
10
20
30
40
50
60
70
80
TEMPERATURE (°C)
Figure 17. Z-Axis Sensitivity at 25°C, VS = 3 V
Figure 20. Z-Axis Sensitivity vs. Temperature,
Eight Parts Soldered to PCB, VS = 3 V
Rev. 0 | Page 8 of 16
90 100
07946-022
0.162
5
07946-019
POPULATION (%)
25
ADXL325
600
CH4: ZOUT, 500mV/DIV
500
400
CH2: X OUT, 500mV/DIV
4
300
2
CH1: POWER, 2V/DIV
1
OUTPUTS ARE OFFSET
FOR CLARITY
100
0
1.5
2.0
2.5
3.0
3.5
4.0
SUPPLY (V)
Figure 21. Typical Current Consumption vs. Supply Voltage
TIME (1ms/DIV)
Figure 22. Typical Turn-On Time, VS = 3 V,
CX = CY = CZ = 0.0047 μF
Rev. 0 | Page 9 of 16
07946-024
3
200
07946-023
CURRENT (µA)
CH3: Y OUT, 500mV/DIV
ADXL325
THEORY OF OPERATION
The ADXL325 is a complete 3-axis acceleration measurement
system. The ADXL325 has a measurement range of ±5 g
minimum. It contains a polysilicon surface micromachined
sensor and signal conditioning circuitry to implement an openloop acceleration measurement architecture. The output signals
are analog voltages that are proportional to acceleration. The
accelerometer can measure the static acceleration of gravity in
tilt-sensing applications, as well as dynamic acceleration, resulting
from motion, shock, or vibration.
MECHANICAL SENSOR
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 180° out-of-phase square waves. Acceleration deflects
the moving mass and unbalances the differential capacitor resulting
in a sensor output whose amplitude is proportional to acceleration.
Phase-sensitive demodulation techniques are then used to determine
the magnitude and direction of the acceleration.
Rather than using additional temperature compensation circuitry,
innovative design techniques ensure that high performance is
built-in to the ADXL325. As a result, there is neither quantization
error nor nonmonotonic behavior, and temperature hysteresis is
very low (typically
