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PDF ADXL212 Data sheet ( Hoja de datos )
| Número de pieza | ADXL212 | |
| Descripción | PWM Output Accelerometer | |
| Fabricantes | Analog Devices | |
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Precision ±2 g Dual Axis,
PWM Output Accelerometer
ADXL212
FEATURES
GENERAL DESCRIPTION
Dual axis accelerometer on a single IC chip
5 mm × 5 mm × 2 mm LCC package
5 mg resolution at 60 Hz
Low power: 700 μA at VS = 5 V (typical)
High zero g bias stability
High sensitivity accuracy
Pulse width modulated digital outputs
X- and Y-axis aligned to within 0.1° (typical)
Bandwidth adjustment with a single capacitor
Single-supply operation
3500 g shock survival
APPLICATIONS
Automotive tilt alarms
Vehicle dynamic control (VDC)/electronic stability program
(ESP) systems
Electronic chassis control
Electronic braking
Data projectors
Navigation
Platform stabilization/leveling
Alarms and motion detectors
High accuracy, 2-axis tilt sensing
The ADXL212 is a high precision, low power, complete dual
axis accelerometer with signal conditioned, duty cycle modulated
outputs, all on a single monolithic IC. The ADXL212 measures
acceleration with a full-scale range of ±2 g (typical). The ADXL212
measures both dynamic acceleration (such as vibration) and
static acceleration (such as gravity).
The outputs are digital signals whose duty cycles (ratio of pulse
width to period) are proportional to acceleration (12.5%/g) in
each of the two sensitive axes. The duty cycle outputs can be
directly measured by a microcontroller without an analog-to-
digital converter (ADC) or glue logic. The output period is
adjustable from 0.5 ms to 10 ms via a single resistor (RSET).
The typical noise floor is 500 μg/√Hz, allowing signals below
5 mg (0.3° of inclination) to be resolved in tilt sensing applica-
tions using narrow bandwidths (<60 Hz).
The user selects the bandwidth of the accelerometer using
Capacitors CX and CY at the XFILT and YFILT pins. Bandwidths
of 0.5 Hz to 500 Hz can be selected to suit the application.
The ADXL212 is available in a 5 mm × 5 mm × 2 mm, 8-lead
hermetic LCC package.
FUNCTIONAL BLOCK DIAGRAM
+VS
VS
CY
YFILT
ADXL212
CDC
SENSOR
AC
AMP
DEMOD
OUTPUT 32kΩ
AMP
OUTPUT
AMP 32kΩ
DCM
YOUT
XOUT
COM
ST
XFILT
CX
T2
RSET
PWM OUTPUT WAVEFORM SAMPLE
t2
t1
Figure 1.
A(g) = (t1/t2 – 0.5)/12.5%
0g = 50% DUTY CYCLE
t2(sec) = RSET/125MΩ
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.
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
©2011 Analog Devices, Inc. All rights reserved.
1 page  
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
ADXL212
TOP VIEW
(Not to Scale)
ST 1
T2 2
COM 3
VS
8
4
YOUT
7 XFILT
6 YFILT
5 XOUT
Figure 3. Pin Configuration
Table 5. Pin Function Descriptions
Pin No.
Mnemonic
1 ST
2 T2
3 COM
4 YOUT
5 XOUT
6 YFILT
7 XFILT
8 VS
Description
Self Test.
Frequency Set. Connect the RSET resistor to ground.
t2 = RSET/125 MΩ
See the Theory of Operation section for details.
Common.
Y Channel Output.
X Channel Output.
Y Channel Filter Pin.
X Channel Filter Pin.
Voltage Supply. 3 V to 5.25 V.
ADXL212
Rev. 0 | Page 5 of 12
5 Page 
USING THE ADXL212 WITH OPERATING
VOLTAGES OTHER THAN 5 V
The ADXL212 is tested and specified at VS = 5 V; however, it
can be powered with VS as low as 3 V or as high as 5.25 V. Some
performance parameters change as the supply voltage varies.
The ADXL212 sensitivity varies proportionally to supply
voltage. At VS = 3 V, the sensitivity is typically 7.5%/g.
The zero g bias output is ratiometric to supply voltage;
therefore, the zero g output is nominally equal to 50% at all
supply voltages.
Self test response in g is roughly proportional to the square of
the supply voltage. Therefore, at VS = 3 V, the self test response
is equivalent to approximately 270 mg (typical), or 6%.
The supply current decreases as the supply voltage decreases.
Typical current consumption at VDD = 3 V is 450 μA.
USING THE ADXL212 AS A DUAL AXIS TILT
SENSOR
A common application of the ADXL212 is tilt measurement. An
accelerometer uses the force of gravity as an input vector to deter-
mine its orientation in space.
ADXL212
An accelerometer is most sensitive to tilt when its sensitive axis
is perpendicular to the force of gravity, that is, parallel to the
surface of the earth. At this orientation, its response to changes
in tilt is highest: its output changes nearly 17.5 mg per degree of
tilt. When the accelerometer is oriented on axis to gravity, that
is, near its +1 g or –1 g reading, the change in output acceleration
per degree of tilt is negligible. At 45°, its output changes by
12.2 mg per degree.
Dual Axis Tilt Sensor: Converting Acceleration to Tilt
When the accelerometer is oriented with both its x-axis and
y-axis parallel to the surface of the earth (reading approximately
0 g), it can be used as a dual axis tilt sensor with a roll axis and a
pitch axis. The output tilt in degrees is calculated as follows:
Pitch = ASIN(AX/1 g)
Roll = ASIN(AY/1 g)
where AX and AY are accelerations in g, ranging from −1 g to +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.
Rev. 0 | Page 11 of 12
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet ADXL212.PDF ] | |
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