Analog Devices ADXL321 Datasheet

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
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

APPLICATIONS

Vibration monitoring and compensation
Abuse event detection
Sports equipment

= 2.4 V (typ)

S

Small and Thin ±18 g Accelerometer

ADXL321

GENERAL DESCRIPTION

The ADXL321 is a small and thin, low power, complete dual­axis 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

and CY at the X

X

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.

OUT

and Y

pins. Bandwidths of

OUT

FUNCTIONAL BLOCK DIAGRAM

+3V

V

S

ADXL321

C

DC

SENSOR

COM ST

AC

AMP

DEMOD

Figure 1.

R

FILT

32kΩ

OUTPUT

AMP

Y
C

OUT

Y

R

FILT

32kΩ

OUTPUT

AMP

X
C

OUT

X

05291-001

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: [phone]
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

www.analog.com

ADXL321

TABLE OF CONTENTS

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

Setting the Bandwidth Using CX and CY................................. 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

REVISION HISTORY

12/04—Revision 0: Initial Version

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

Rev. 0 | Page 2 of 16

ADXL321

SPECIFICATIONS1

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 ±18

Nonlinearity % of full scale ±0.2 %

Package Alignment Error ±1 Degrees

Alignment Error X sensor to Y sensor ±0.1 Degrees

Cross Axis Sensitivity ±2 %
SENSITIVITY (RATIOMETRIC)2 Each axis

Sensitivity at X

Sensitivity Change due to Temperature3 V

, Y

V

OUT

OUT

= 3 V 51 57 63 mV/g

S

= 3 V 0.01 %/°C

S

ZERO g BIAS LEVEL (RATIOMETRIC) Each axis

0 g Voltage at X

, Y

V

OUT

OUT

= 3 V 1.4 1.5 1.6 V

S

0 g Offset vs. Temperature ±2 mg/°C
NOISE PERFORMANCE

Noise Density @ 25°C 320 µg/√Hz rms
FREQUENCY RESPONSE4

CX, CY Range5 0.002 10 µF

R

Tolerance 32 ± 15% kΩ

FILT

Sensor Resonant Frequency 5.5 kHz
SELF-TEST6

Logic Input Low 0.6 V

Logic Input High 2.4 V

ST Input Resistance to Ground 50 kΩ

Output Change at X

, Y

Self-test 0 to 1 18 mV

OUT

OUT

OUTPUT AMPLIFIER

Output Swing Low No load 0.3 V

Output Swing High No load 2.6 V
POWER SUPPLY

Operating Voltage Range 2.4 6 V

Quiescent Supply Current 0.49 mA

Turn-On Time7 20 ms
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.

g

Rev. 0 | Page 3 of 16

ADXL321

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

Acceleration (Any Axis, Unpowered) 10,000 g
Acceleration (Any Axis, Powered) 10,000 g
VS −0.3 V to +7.0 V
All Other Pins

Output Short-Circuit Duration
(Any Pin to Common) Indefinite

Operating Temperature Range −55°C to +125°C
Storage Temperature −65°C to +150°C

(COM − 0.3 V) to

+ 0.3 V)

(V

S

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 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.

Rev. 0 | Page 4 of 16

ADXL321

V

V

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

NC

COM

NC

1

ST

2

3

S

16 15 14 13

ADXL321

TOP VIEW

(Not to Scale)

NC

S

X

12

OUT

11

NC

Y

10

OUT

NC

4

5678

COM

COM

NC = NO CONNECT

COM

NC

NC

9

05291-002

Figure 2. Pin Configuration

Table 3. Pin Function Descriptions

Pin No. Mnemonic Description

1, 4, 8, 9, 11, 13, 16 NC Do Not Connect
2 ST Self-Test
3, 5 to 7 COM Common
10 Y
12 X

Y Channel Output

OUT

X Channel Output

OUT

14, 15 VS 2.4 V to 6 V

Rev. 0 | Page 5 of 16