ADIS16003

Rev. 0 | Page 13 of 16

POWER SUPPLY DECOUPLING

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

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,

much as ±25% of its nominal value (32 kΩ); thus, the band-

width varies accordingly.

allowable.

Bandwidth (Hz)

Capacitor (μF)

1

4.7

10

0.47

50

0.10

100

0.047

200

0.022

400

0.01

2250

0

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.

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

rmsNoise = (110 μg/√Hz) x (√(BW x 1.6))

At 100 Hz, the noise is

rmsNoise = (110 μg/√Hz) x (√(100 x 1.6)) =1.4 mg

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

Percentage 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%