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ADXL320 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADXL320
Beschreibung Small and Thin 5 g Accelerometer
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 16 Seiten
ADXL320 Datasheet, Funktion
www.DataSheet4U.com
FEATURES
Small and thin
4 mm × 4 mm × 1.45 mm LFCSP package
2 mg resolution at 60 Hz
Wide supply voltage range: 2.4 V to 5.25 V
Low power: 350 µA at VS = 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
APPLICATIONS
Cost-sensitive motion- and tilt-sensing applications
Smart hand-held devices
Mobile phones
Sports and health-related devices
PC security and PC peripherals
Small and Thin ±5 g Accelerometer
ADXL320
GENERAL DESCRIPTION
The ADXL320 is a low cost, 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 ±5 g (typical). It can also
measure both dynamic acceleration (vibration) and static
acceleration (gravity).
The ADXL320’s typical noise floor is 250 µg/√Hz, allowing
signals below 2 mg to be resolved in tilt-sensing applications
using narrow bandwidths (<60 Hz).
The user selects the bandwidth of the accelerometer using
capacitors CX and CY at the XOUT and YOUT pins. Bandwidths of
0.5 Hz to 2.5 kHz may be selected to suit the application.
The ADXL320 is available in a very thin 4 mm × 4 mm ×
1.45 mm, 16-lead, plastic LFCSP.
FUNCTIONAL BLOCK DIAGRAM
+3V
VS
ADXL320
CDC
SENSOR
COM
AC
AMP
DEMOD
OUTPUT
AMP
OUTPUT
AMP
RFILT
32k
RFILT
32k
ST
YOUT
XOUT
CY CX
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.






ADXL320 Datasheet, Funktion
ADXL320
TP
TL TSMAX
TSMIN
RAMP-UP
tP
CRITICAL ZONE
TL TO TP
tL
tS
PREHEAT
RAMP-DOWN
t25°C TO PEAK
TIME
Figure 3. Recommended Soldering Profile
Table 4. Recommended Soldering Profile
Profile Feature
Average Ramp Rate (TL to TP)
Preheat
Minimum Temperature (TSMIN)
Minimum Temperature (TSMAX)
Time (TSMIN to TSMAX), tS
TSMAX to TL
Ramp-Up Rate
Time Maintained Above Liquidous (TL)
Liquidous Temperature (TL)
Time (tL)
Peak Temperature (TP)
Time within 5°C of Actual Peak Temperature (tP)
Ramp-Down Rate
Time 25°C to Peak Temperature
Sn63/Pb37
3°C/s max
100°C
150°C
60 s − 120 s
3°C/s
183°C
60 s − 150 s
240°C + 0°C/−5°C
10 s − 30 s
6°C/s max
6 min max
Pb-Free
3°C/s max
150°C
200°C
60 s − 150 s
3°C/s
217°C
60 s − 150 s
260°C + 0°C/−5°C
20 s − 40 s
6°C/s max
8 min max
Rev. 0 | Page 6 of 16

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ADXL320 pdf, datenblatt
ADXL320
APPLICATIONS
POWER SUPPLY DECOUPLING
For most applications, a single 0.1 µF capacitor, CDC, adequately
decouples the accelerometer from noise on the power supply.
However, in some cases, particularly where noise is present at
the 140 kHz internal clock frequency (or any harmonic
thereof), noise on the supply may cause interference on the
ADXL320 output. If additional decoupling is needed, a 100 Ω
(or smaller) resistor or ferrite bead may be inserted in the
supply line. Additionally, a larger bulk bypass capacitor (in the
1 µF to 4.7 µF range) may be added in parallel to CDC.
SETTING THE BANDWIDTH USING CX AND CY
The ADXL320 has provisions for band-limiting the XOUT and
YOUT pins. Capacitors must be added at these pins to implement
low-pass filtering for antialiasing and noise reduction. The
equation for the 3 dB bandwidth is
F−3 dB = 1/(2π(32 kΩ) × C(X, Y))
or more simply,
F–3 dB = 5 µF/C(X, Y)
The tolerance of the internal resistor (RFILT) typically varies as
much as ±15% of its nominal value (32 kΩ), and the bandwidth
varies accordingly. A minimum capacitance of 2000 pF for CX
and CY is required in all cases.
Table 5. Filter Capacitor Selection, CX and CY
Bandwidth (Hz)
Capacitor (µF)
1 4.7
10 0.47
50 0.10
100 0.05
200 0.027
500 0.01
SELF-TEST
The ST pin controls the self-test feature. When this pin is set to
VS, an electrostatic force is exerted on the accelerometer beam.
The resulting movement of the beam allows the user to test if
the accelerometer is functional. The typical change in output is
315 mg (corresponding to 55 mV). This pin may be left open-
circuit or connected to common (COM) in normal use.
The ST pin should never be exposed to voltages greater than
VS + 0.3 V. If this cannot be guaranteed due to the system design
(for instance, if there are multiple supply voltages), then a low
VF clamping diode between ST and VS is recommended.
DESIGN TRADE-OFFS FOR SELECTING FILTER
CHARACTERISTICS: THE NOISE/BW TRADE-OFF
The accelerometer bandwidth selected ultimately determines
the measurement resolution (smallest detectable acceleration).
Filtering can be used to lower the noise floor, which improves
the resolution of the accelerometer. Resolution is dependent on
the analog filter bandwidth at XOUT and YOUT.
The output of the ADXL320 has a typical bandwidth of 2.5 kHz.
The user must filter the signal at this point to limit aliasing
errors. The analog bandwidth must be no more than half the
A/D sampling frequency to minimize aliasing. The analog
bandwidth may be further decreased to reduce noise and
improve resolution.
The ADXL320 noise has the characteristics of white Gaussian
noise, which contributes equally at all frequencies and is
described in terms of µg/√Hz (the noise is proportional to the
square root of the accelerometer’s bandwidth). The user should
limit bandwidth to the lowest frequency needed by the
application in order to maximize the resolution and dynamic
range of the accelerometer.
With the single-pole, roll-off characteristic, the typical noise of
the ADXL320 is determined by
rmsNoise = (250 µg/ Hz )×( BW ×1.6 )
At 100 Hz bandwidth the noise will be
rmsNoise = (250 µg/ Hz )×( 100 ×1.6 ) = 3.2mg
Often, the peak value of the noise is desired. Peak-to-peak noise
can only be estimated by statistical methods. Table 6 is useful
for estimating the probabilities of exceeding various peak
values, given the rms value.
Table 6. Estimation of Peak-to-Peak Noise
Peak-to-Peak Value
% of Time That Noise Exceeds
Nominal Peak-to-Peak Value
2 × rms
32
4 × rms
4.6
6 × rms
0.27
8 × rms
0.006
Rev. 0 | Page 12 of 16

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