AD22151(Rev0) 데이터 시트보기 (PDF) - Analog Devices
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AD22151 Datasheet PDF : 8 Pages
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AD22151
Knowing the values of R3 and R4 from above, and noting Equa-
tion 2, the parallel combination of R2 and R4 required is:
( ) 85 kΩ = 6.071 kΩ
15 –1
Thus:
R2
=
1
6.071
kΩ
1
–
1
141.666
kΩ
=
6.342
kΩ
NOISE
The principle noise component in the sensor is thermal noise
from the Hall cell. Clock feedthrough into the output signal is
largely suppressed with application of a supply bypass capacitor.
Figure 12 shows the power spectral density (PSD) of the output
signal for a gain of 5 mV/Gauss. The effective bandwidth of the
sensor is approximately 5.7 kHz. This is shown by Figure 13
small signal bandwidth vs. gain. The PSD indicates an rms
noise voltage of 2.8 mV within the 3 dB bandwidth of the sen-
sor. A wideband measurement of 250 MHz indicates 3.2 mV
rms (see Figure 14a).
In many position sensing applications bandwidth requirements
can be as low as 100 Hz. Passing the output signal through an
LP filter, for example 100 Hz, would reduce the rms noise volt-
age to ≈1 mV. A dominant pole may be introduced into the
output amplifier response by connection of a capacitor across
feedback resistor R3, as a simple means of reducing noise at the
expense of bandwidth. Figure 14b indicates the output signal of
a 5 mV/G sensor bandwidth limited to 180 Hz with a 0.01 µF
feedback capacitor.
Note: Measurements taken with 0.1 µF decoupling capacitor
between VCC and GND at +25°C.
B MARKER X 64Hz
100
H
Y: 3.351 H
LOGMAG
5 dB
/div
7
6
3dB FREQ. (kHz)
5
4
3
2
1
0
1
2
3
4
5
6
GAIN – mV/GAUSS
Figure 13. Small-Signal Gain Bandwidth
TEK STOP: 25.0 kS/s [
3ACQS
T
CH2 PK-PK
19.2mV
2
T
CH2 10.0mV BW M2.00ms
Figure 14a. Peak-to-Peak Full Bandwidth (10 mV/Division)
TEK STOP: 25.0 kS/s [
7ACQS
T
CH2 PK-PK
4.4mV
2
T
1
H
START: 64 Hz
NOISE: PSD (8 mV/GAUSS)
STOP: 25.6 kHz
RMS: 64
Figure 12. Power Spectral Density (5 mV/G)
CH2 10.0mV BW M2.00ms
Figure 14b. Peak-to-Peak 180 Hz Bandwidth
(10 mV/Division)
–6–
REV. 0
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