ADIS16003PCB AD [Analog Devices], ADIS16003PCB Datasheet - Page 13

• Manufacturer Part Number: ADIS16003PCB
• Manufacturer: AD [Analog Devices]

POWER SUPPLY DECOUPLING
For most applications, a single 0.1 μF capacitor (C
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
ADIS16003 output. If additional decoupling is needed, ferrite
beads may be inserted in the supply line of the ADIS16003.
Additionally, a larger bulk bypass capacitor (in the 1 μF to 22 μF
range) may be added in parallel to C
SETTING THE BANDWIDTH USING C
The ADIS16003 has provisions for band-limiting the acceler-
ometer. Capacitors can be added at the XFILT and YFILT pins
to implement further 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 ±25% of its nominal value (32 kΩ); thus, the band-
width varies accordingly.
A minimum capacitance of 0 pF for C
allowable.
Table 9. Filter Capacitor Selection, C
Bandwidth (Hz)
1
10
50
100
200
400
2250
SELECTING FILTER CHARACTERISTICS:
THE NOISE/BANDWIDTH 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 XFILT and YFILT.
The ADIS16003 has a typical bandwidth of 2.25 kHz with no
external filtering. The analog bandwidth may be further
decreased to reduce noise and improve resolution.
F
F
−3dB
−3dB
= 1/(2π(32 kΩ) × (C
= 5 μF/(C
(XFILT, YFILT)
+ 2200 pF)
(XFILT, YFILT)
Capacitor (μF)
4.7
0.47
0.10
0.047
0.022
0.01
0
DC.
+ 2200 pF))
XFILT
XFILT
FILT
) can vary typically as
and C
and C
XFILT
YFILT
YFILT
DC
AND C
) adequately
is
YFILT
Rev. 0 | Page 13 of 16
The ADIS16003 noise has the characteristics of white Gaussian
noise, which contributes equally at all frequencies and is
described in terms of μg/√Hz (that is, 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 ADIS16003 is determined by
At 100 Hz, the noise is
Often, the peak value of the noise is desired. Peak-to-peak noise
can only be estimated by statistical methods. Table 10 is useful
for estimating the probabilities of exceeding various peak
values, given the rms value.
Table 10. Estimation of Peak-to-Peak Noise
Peak-to-Peak
Value
2 × rms
4 × rms
6 × rms
8 × rms
rmsNoise = (110 μg/√Hz) x (√(BW x 1.6))
rmsNoise = (110 μg/√Hz) x (√(100 x 1.6)) =1.4 mg
Percentage of Time that Noise Exceeds
Nominal Peak-to-Peak Value
32%
4.6%
0.27%
0.006%
ADIS16003