AD7747 View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
AD7747 Datasheet PDF : 28 Pages
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AD7747
OUTPUT NOISE AND RESOLUTION SPECIFICATIONS
The AD7747 resolution is limited by noise. The noise
performance varies with the selected conversion time.
Table 5 shows typical noise performance and resolution for the
capacitive channel. These numbers were generated from 1000
data samples acquired in continuous conversion mode, at an
excitation of 16 kHz, ±VDD × 3/8, and with all CIN and SHLD
pins connected only to the evaluation board (no external
capacitors).
Table 6 and Table 7 show typical noise performance and
resolution for the voltage channel. These numbers were
generated from 1000 data samples acquired in continuous
conversion mode with VIN pins shorted to ground.
RMS noise represents the standard deviation and p-p noise
represents the difference between minimum and maximum
results in the data. Effective resolution is calculated from rms
noise, and p-p resolution is calculated from p-p noise.
Table 5. Typical Capacitive Input Noise and Resolution vs. Conversion Time (Bold line represents default setting)
Conversion
Time (ms)
22.0
23.9
40.0
76.0
124.0
154.0
184.0
219.3
Output Data
Rate (Hz)
45.5
41.9
25.0
13.2
8.1
6.5
5.4
4.6
−3 dB Frequency
(Hz)
43.6
39.5
21.8
10.9
6.9
5.3
4.4
4.0
RMS Noise
(aF/√Hz)
28.8
23.2
11.1
11.2
11.0
10.4
10.0
9.0
RMS
Noise (aF)
190
146
52
37
29
24
21
18
P-P
Noise (aF)
821
725
411
262
174
173
141
126
Effective Resolution
(Bits)
16.4
16.8
18.3
18.7
19.1
19.3
19.6
19.9
P-P Resolution
(Bits)
14.3
14.5
15.3
15.9
16.5
16.5
16.8
17.0
Table 6. Typical Voltage Input Noise and Resolution vs. Conversion Time, Internal Voltage Reference
Conversion
Time (ms)
20.1
32.1
62.1
122.1
Output Data
Rate (Hz)
49.8
31.2
16.1
8.2
−3 dB Frequency
(Hz)
26.4
15.9
8.0
4.0
RMS Noise
(μV)
11.4
7.1
4.0
3.0
P-P Noise
(μV)
62
42
28
20
Effective Resolution
(Bits)
17.6
18.3
19.1
19.5
P-P Resolution
(Bits)
15.2
15.7
16.3
16.8
Table 7. Typical Voltage Input Noise and Resolution vs. Conversion Time, External 2.5 V Voltage Reference
Conversion
Time (ms)
20.1
32.1
62.1
122.1
Output Data
Rate (Hz)
49.8
31.2
16.1
8.2
−3 dB Frequency
(Hz)
26.4
15.9
8.0
4.0
RMS Noise
(μV)
14.9
6.3
3.3
2.1
P-P Noise
(μV)
95
42
22
15
Effective Resolution
(Bits)
18.3
19.6
20.5
21.1
P-P Resolution
(Bits)
15.6
16.8
17.7
18.3
Rev. 0 | Page 11 of 28
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