ADXL323KCPZ-RL Analog Devices Inc, ADXL323KCPZ-RL Datasheet - Page 12

• Manufacturer Part Number: ADXL323KCPZ-RL
• Description: IC,Acceleration Detector,LLCC,16PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Series: iMEMS®r

Specifications of ADXL323KCPZ-RL

• Axis: X, Y
• Acceleration Range: ±3.6g
• Sensitivity: 300mV/g
• Voltage - Supply: 1.8 V ~ 5.25 V
• Output Type: Analog
• Bandwidth: 1Hz ~ 500Hz Selectable
• Mounting Type: Surface Mount
• Package / Case: 16-LQFN, CSP Exposed Pad
• Family Name: ADXL323
• Package Type: LFCSP EP
• Operating Supply Voltage (min): 1.8V
• Operating Supply Voltage (typ): 2.5/3.3/5V
• Operating Supply Voltage (max): 5.25V
• Operating Temperature (min): -25C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Product Depth (mm): 4mm
• Product Height (mm): 1.43mm
• Product Length (mm): 4mm
• Mounting: Surface Mount
• Pin Count: 16
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Interface: -
• Lead Free Status / Rohs Status: Compliant
• Other names: ADXL323KCPZ-RLTR

ADXL323
APPLICATIONS
POWER SUPPLY DECOUPLING
For most applications, a single 0.1 μF capacitor, C
close to the ADXL323 supply pins adequately decouples the
accelerometer from noise on the power supply. However, in
applications where noise is present at the 50 kHz internal clock
frequency (or any harmonic thereof), additional care in power
supply bypassing is required because this noise can cause errors
in acceleration measurement. If additional decoupling is needed,
a 100 Ω (or smaller) resistor or ferrite bead can be inserted in
the supply line. Additionally, a larger bulk bypass capacitor
(1 μF or greater) can be added in parallel to C
connection from the ADXL323 ground to the power supply
ground is low impedance because noise transmitted through
ground has an effect similar to that of noise transmitted
through V
SETTING THE BANDWIDTH USING C
The ADXL323 has provisions for band limiting the X
and the Y
implement low-pass filtering for antialiasing and noise
reduction. The equation for the 3 dB bandwidth is
or more simply
The tolerance of the internal resistor (R
much as ±15% of its nominal value (32 kΩ), and the bandwidth
varies accordingly. A minimum capacitance of 0.0047 μF for C
C
Table 5. Filter Capacitor Selection, C
Bandwidth (Hz)
1
10
50
100
200
500
SELF TEST
The ST pin controls the self-test feature. When this pin is set to
V
The resulting movement of the beam allows the user to test if
the accelerometer is functional. The typical change in output is
−500 mg (corresponding to −150 mV) in the X-axis, and 500 mg
(or 150 mV) on the Y-axis. This ST pin can be left open circuit
or connected to common (COM) in normal use.
Y
S
, an electrostatic force is exerted on the accelerometer beam.
, and C
F
F
−3 dB
–3 dB
OUT
Z
= 5 μF/C
= 1/(2π(32 kΩ) × C
S
.
is recommended in all cases.
pin. Capacitors must be added at these pins to
(X, Y, Z)
(X, Y, Z)
)
Capacitor (μF)
4.7
0.47
0.10
0.05
0.027
0.01
X
FILT
, C
) typically varies as
Y
, and C
X
DC
, C
. Ensure that the
DC
Y
, AND C
Z
, placed
OUT
pin
Z
Rev. 0 | Page 12 of 16
X
,
Never expose the ST pin to voltages greater than V
If this cannot be guaranteed due to the system design (for
example, if there are multiple supply voltages), a low V
clamping diode between ST and V
DESIGN TRADE-OFFS FOR SELECTING FILTER
CHARACTERISTICS: THE NOISE/BW TRADE-OFF
The selected accelerometer bandwidth ultimately determines
the measurement resolution (smallest detectable acceleration).
Filtering can be used to lower the noise floor to improve the
resolution of the accelerometer. Resolution is dependent on the
analog filter bandwidth at X
The output of the ADXL323 has a typical bandwidth of greater
than 1600 Hz. The user must filter the signal at this point to
limit aliasing errors. The analog bandwidth must be no more
than half the analog-to-digital sampling frequency to minimize
aliasing. The analog bandwidth can be further decreased to
reduce noise and improve resolution.
The ADXL323 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 bandwidth). The user should
limit bandwidth to the lowest frequency needed by the applica-
tion to maximize the resolution and dynamic range of the
accelerometer.
With the single-pole, roll-off characteristic, the typical noise of
the ADXL323 is determined by
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
2 × rms
4 × rms
6 × rms
8 × rms
USE WITH OPERATING VOLTAGES OTHER THAN 3 V
The ADXL323 is tested and specified at V
can be powered with V
Note that some performance parameters change as the supply
voltage is varied.
rms
Noise
=
Noise
S
Density
as low as 1.8 V or as high as 5.25 V.
% of Time that Noise Exceeds
Nominal Peak-to-Peak Value
32
4.6
0.27
0.006
OUT
and Y
×
(
S
is recommended.
BW
OUT
.
×
S
1.6
= 3 V; however, it
)
S
+ 0.3 V.
F