Small and Thin ±18
g
Accelerometer
ADXL321
FEATURES
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 V
S
= 2.4 V (typ)
Good zero
g
bias stability
Good sensitivity accuracy
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
GENERAL DESCRIPTION
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 ±18
g
(typical). It can also
measure both dynamic acceleration (vibration) and static
acceleration (gravity).
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).
The user selects the bandwidth of the accelerometer using
capacitors C
X
and C
Y
at the X
OUT
and Y
OUT
pins. Bandwidths of
0.5 Hz to 2.5 kHz may be selected to suit the application.
The ADXL321 is available in a very thin 4 mm × 4 mm ×
1.45 mm, 16-lead, plastic LFCSP.
APPLICATIONS
Vibration monitoring and compensation
Abuse event detection
Sports equipment
FUNCTIONAL BLOCK DIAGRAM
+3V
V
S
ADXL321
C
DC
AC
AMP
SENSOR
DEMOD
OUTPUT
AMP
OUTPUT
AMP
R
FILT
32kΩ
R
FILT
32kΩ
COM
ST
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: 781.326.8703
© 2004 Analog Devices, Inc. All rights reserved.
05291-001
YOUT
C
Y
XOUT
C
X
ADXL321
TABLE OF CONTENTS
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 4
ESD Caution.................................................................................. 4
Pin Configuration and Function Descriptions............................. 5
Typical Performance Characteristics (V
S
= 3.0 V) ....................... 7
Theory of Operation ...................................................................... 11
Performance ................................................................................ 11
Applications..................................................................................... 12
Power Supply Decoupling ......................................................... 12
Setting the Bandwidth Using C
X
and C
Y
................................. 12
Self-Test ....................................................................................... 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
ADXL321
SPECIFICATIONS
1
T
A
= 25°C, V
S
= 3 V, C
X
= C
Y
= 0.1 µF, Acceleration = 0
g,
unless otherwise noted.
Table 1.
Parameter
SENSOR INPUT
Measurement Range
Nonlinearity
Package Alignment Error
Alignment Error
Cross Axis Sensitivity
SENSITIVITY (RATIOMETRIC)
2
Sensitivity at X
OUT
, Y
OUT
Sensitivity Change due to Temperature
3
ZERO
g
BIAS LEVEL (RATIOMETRIC)
0
g
Voltage at X
OUT
, Y
OUT
0
g
Offset vs. Temperature
NOISE PERFORMANCE
Noise Density
FREQUENCY RESPONSE
4
C
X
, C
Y
Range
5
R
FILT
Tolerance
Sensor Resonant Frequency
SELF-TEST
6
Logic Input Low
Logic Input High
ST Input Resistance to Ground
Output Change at X
OUT
, Y
OUT
OUTPUT AMPLIFIER
Output Swing Low
Output Swing High
POWER SUPPLY
Operating Voltage Range
Quiescent Supply Current
Turn-On Time
7
TEMPERATURE
Operating Temperature Range
Conditions
Each axis
% of full scale
X sensor to Y sensor
Each axis
V
S
= 3 V
V
S
= 3 V
Each axis
V
S
= 3 V
Min
Typ
±18
±0.2
±1
±0.1
±2
51
57
0.01
1.5
±2
320
0.002
32 ± 15%
5.5
0.6
2.4
50
18
0.3
2.6
2.4
0.49
20
−20
+70
6
10
63
Max
Unit
g
%
Degrees
Degrees
%
mV/g
%/°C
V
mg/°C
µg/√Hz rms
µF
kΩ
kHz
V
V
kΩ
mV
V
V
V
mA
ms
°C
1.4
1.6
@ 25°C
Self-test 0 to 1
No load
No load
1
2
All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed.
Sensitivity is essentially ratiometric to V
S
.
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 (C
X
, C
Y
).
5
Bandwidth = 1/(2 × π × 32 kΩ × C). For C
X
, C
Y
= 0.002 µF, bandwidth = 2500 Hz. For C
X
, C
Y
= 10 µF, bandwidth = 0.5 Hz. Minimum/maximum values are not tested.
6
Self-test response changes cubically with V
S
.
7
Larger values of C
X
, C
Y
increase turn-on time. Turn-on time is approximately 160 × C
X
or C
Y
+ 4 ms, where C
X
, C
Y
are in µF.
Rev. 0 | Page 3 of 16
ADXL321
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Acceleration (Any Axis, Unpowered)
Acceleration (Any Axis, Powered)
V
S
All Other Pins
Output Short-Circuit Duration
(Any Pin to Common)
Operating Temperature Range
Storage Temperature
Rating
10,000
g
10,000
g
−0.3 V to +7.0 V
(COM − 0.3 V) to
(V
S
+ 0.3 V)
Indefinite
−55°C to +125°C
−65°C to +150°C
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.
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
ADXL321
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
NC
16
V
S
15
V
S
14
NC
13
12
NC
1
ST
2
COM
3
NC
4
5
6
7
8
X
OUT
NC
Y
OUT
NC
ADXL321
TOP VIEW
(Not to Scale)
11
10
9
COM
COM
COM
NC = NO CONNECT
NC
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
Pin No.
1, 4, 8, 9, 11, 13, 16
2
3, 5 to 7
10
12
14, 15
Mnemonic
NC
ST
COM
Y
OUT
X
OUT
V
S
Description
Do Not Connect
Self-Test
Common
Y Channel Output
X Channel Output
2.4 V to 6 V
Rev. 0 | Page 5 of 16
05291-002
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