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PDF ADXL344 Data sheet ( Hoja de datos )
| Número de pieza | ADXL344 | |
| Descripción | Ultralow Power Digital MEMS Accelerometer | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Data Sheet
3-Axis, ±2 g/±4 g/±8 g/±16 g Ultralow
Power Digital MEMS Accelerometer
ADXL344
FEATURES
Multipurpose accelerometer with 10- to 13-bit resolution for
use in a wide variety of applications
Digital output accessible via SPI (3- and 4-wire) and I2C
Built-in motion detection features make tap, double-tap,
activity, inactivity, orientation, and free-fall detection
trivial
User-adjustable thresholds
Interrupts independently mappable to two interrupt pins
Low power operation down to 23 µA and embedded FIFO for
reducing overall system power
Wide supply and I/O voltage range: 1.7 V to 2.75 V
Wide operating temperature range (−40°C to +85°C)
10,000 g shock survival
Small, thin Pb free, RoHS compliant 3 mm × 3 mm × 0.95 mm
LGA package
APPLICATIONS
Handsets
Gaming and pointing devices
Hard disk drive (HDD) protection
GENERAL DESCRIPTION
The ADXL344 is a versatile 3-axis, digital-output, low g MEMS
accelerometer. Selectable measurement range and bandwidth and
configurable, built-in motion detection make it suitable for sensing
acceleration in a wide variety of applications. Robustness to
10,000 g of shock and a wide temperature range (−40°C to +85°C)
enable use of the accelerometer even in harsh environments.
The ADXL344 measures acceleration with high resolution (13-bit)
measurement at up to ±16 g. Digital output data is formatted as
16-bit twos complement and is accessible through either a SPI
(3- or 4-wire) or I2C digital interface. The ADXL344 can
measure the static acceleration of gravity in tilt-sensing appli-
cations, as well as dynamic acceleration resulting from motion
or shock. Its high resolution (3.9 mg/LSB) enables measurement
of inclination changes less than 1.0°.
Several special sensing functions are provided. Activity and
inactivity sensing detect the presence or lack of motion. Tap
sensing detects single and double taps in any direction. Free-fall
sensing detects if the device is falling. Orientation detection
reports four- and six-position orientation and can trigger an
interrupt upon change in orientation. These functions can be
mapped individually to either of two interrupt output pins.
An integrated memory management system with a 32-level first in,
first out (FIFO) buffer can be used to store data to minimize host
processor activity and lower overall system power consumption.
The ADXL344 is supplied in a small, thin, 3 mm × 3 mm ×
0.95 mm, 16-terminal, plastic package.
ADXL344
FUNCTIONAL BLOCK DIAGRAM
VS VDD I/O
POWER
MANAGEMENT
3-AXIS
SENSOR
SENSE
ELECTRONICS
ADC
DIGITAL
FILTER
CONTROL
AND
INTERRUPT
LOGIC
INT1
INT2
32-LEVEL
FIFO
SERIAL I/O
SDA/SDI/SDIO
SDO/ALT
ADDRESS
SCL/SCLK
GND
CS
Figure 1.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor 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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
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
©2012 Analog Devices, Inc. All rights reserved.
1 page  
ADXL344
Data Sheet
Parameter
TEMPERATURE
Operating Temperature Range
WEIGHT
Device Weight
Test Conditions/Comments Min1
−40
Typ 2
18
Max1
+85
Unit
°C
mg
1 All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed.
2 The typical specifications shown are for at least 68% of the population of parts and are based on the worst case of mean ±1 σ except for 0 g output and sensitivity,
which represents the target value. For 0 g offset and sensitivity, the deviation from the ideal describes the worst case of mean ±1 σ.
3 Cross-axis sensitivity is defined as coupling between any two axes.
4 Bandwidth is the −3 dB frequency and is half the output data rate bandwidth = ODR/2.
5 The output format for the 3200 Hz and 1600 Hz ODRs is different from the output format for the remaining ODRs. This difference is described in the Data Formatting of
Upper Data Rates section.
6 Output data rates below 6.25 Hz exhibit additional offset shift with increased temperature, depending on selected output data rate. Refer to the Offset Performance at
Lowest Data Rates section for details.
7 These are typical values for the lowest and highest output data rate settings.
8 Self-test change is defined as the output (g) when the SELF_TEST bit = 1 (in the DATA_FORMAT register, Address 0x31) minus the output (g) when the SELF_TEST bit = 0.
Due to device filtering, the output reaches its final value after 4 × τ when enabling or disabling self-test, where τ = 1/(data rate). The part must be in normal power
operation (LOW_POWER bit = 0 in the BW_RATE register, Address 0x2C) for self-test to operate correctly.
9 Turn-on and wake-up times are determined by the user-defined bandwidth. At a 100 Hz data rate, the turn-on and wake-up times are each approximately 11.1 ms. For
other data rates, the turn-on and wake-up times are each approximately τ + 1.1 in milliseconds, where τ = 1/(data rate).
Rev. 0 | Page 4 of 40
5 Page 
ADXL344
Data Sheet
THEORY OF OPERATION
The ADXL344 is a complete 3-axis acceleration measurement
system with a selectable measurement range of ±2 g, ±4 g, ±8 g,
or ±16 g. It measures both dynamic acceleration resulting from
motion or shock and static acceleration, such as gravity, which
allows the device to be used as a tilt 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 forces due to applied acceleration.
Deflection of the structure is measured using differential capacitors
that consist of independent fixed plates and plates attached to the
moving mass. Acceleration deflects the proof mass and unbalances
the differential capacitor, resulting in a sensor output with an
amplitude proportional to acceleration. Phase-sensitive de-
modulation is used to determine the magnitude and polarity
of the acceleration.
POWER SEQUENCING
Power can be applied to VS or VDD I/O in any sequence without
damaging the ADXL344. All possible power-on modes are
summarized in Table 6. The interface voltage level is set with
the interface supply voltage, VDD I/O, which must be present to
ensure that the ADXL344 does not create a conflict on the
communication bus. For single-supply operation, VDD I/O can be
the same as the main supply, VS. In a dual-supply application,
however, VDD I/O can differ from VS to accommodate the desired
interface voltage, as long as VS is greater than or equal to VDD I/O.
After VS is applied, the device enters standby mode, where power
consumption is minimized and the device waits for VDD I/O to be
applied and for the command to enter measurement mode to be
received. (This command can be initiated by setting the measure
bit (Bit D3) in the POWER_CTL register (Address 0x2D).) In
addition, any register can be written to or read from to configure
the part while the device is in standby mode. It is recommended
to configure the device in standby mode and then to enable
measurement mode. Clearing the measure bit returns the
device to the standby mode.
Table 6. Power Sequencing
Condition
Power Off
Bus Disabled
Bus Enabled
Standby or
Measurement Mode
VS
Off
On
Off
On
VDD I/O
Off
Off
On
On
Description
The device is completely off, but there is a potential for a communication
bus conflict.
The device is on in standby mode, but communication is unavailable and
will create a conflict on the communication bus. The duration of this state
should be minimized during power-up to prevent a conflict.
No functions are available, but the device will not create a conflict on the
communication bus.
At power-up, the device is in standby mode, awaiting a command to
enter measurement mode, and all sensor functions are off. After the
device is instructed to enter measurement mode, all sensor functions are
available.
Rev. 0 | Page 10 of 40
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| PDF Descargar | [ Datasheet ADXL344.PDF ] | |
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