ADIS16006

Rev. 0 | Page 13 of 16

SETTING THE BANDWIDTH

The ADIS16006 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 bandwidth

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 ADIS16006 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 ADIS16006 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 applica-

tion to maximize the resolution and dynamic range of the

accelerometer.

With the single pole roll-off characteristic, the typical noise of

the ADIS16006 is determined by

rmsNoise = (200 μg/root Hz) x (root (BW x 1.57))

At 100 Hz, the noise is

rmsNoise = (200 μg/root Hz) x (root (100 x 1.57)) =2.5 mg

Often, the peak value of the noise is desired. Peak-to-peak noise

can be estimated only 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%

12

4

10

11

6

5

8

9

7

3

2

1

8

9

7

3

2

1

12

4

10

11

6

5

Top View

Not to Scale

DIGITAL OUTPUT (IN LSBs)

X-AXIS: 1792

Y-AXIS: 2048

DIGITAL OUTPUT (IN LSBs)

X-AXIS: 2304

Y-AXIS: 2048

DIGITAL OUTPUT (IN LSBs)

X-AXIS: 2048

Y-AXIS: 2304

DIGITAL OUTPUT (IN LSBs)

X-AXIS: 2048

Y-AXIS: 1792

DIGITAL OUTPUT (IN LSBs)

X-AXIS: 2048

Y-AXIS: 2048

Figure 23. Output Response vs. Orientation