AD7798/AD7799
Data Sheet
OUTPUT NOISE AND RESOLUTION SPECIFICATIONS
AD7798
Table 5 shows the AD7798 output rms noise for some update
rates and gain settings. The numbers given are for the bipolar
input range with a 2.5 V reference. These numbers are typical
and are generated with a differential input voltage of 0 V. Table 6
shows the effective resolution, and the output peak-to-peak
resolution is shown in parentheses. It is important to note that
the effective resolution is calculated using the rms noise, whereas
the peak-to-peak resolution is based on the peak-to-peak noise.
The peak-to-peak resolution represents the resolution for which
there is no code flicker. These numbers are typical and are
rounded to the nearest LSB.
Table 5. Output RMS Noise (µV) vs. Gain and Output Update Rate for the AD7798 Using a 2.5 V Reference
Update Rate
4.17 Hz
8.33 Hz
16.7 Hz
33.2 Hz
62 Hz
123 Hz
242 Hz
470 Hz
Gain of 1
Gain of 2
Gain of 4
Gain of 8
0.22
0.26
0.36
0.5
0.58
1
1.96
1.79
Gain of 16
Gain of 32
0.065
0.078
0.11
0.17
0.2
0.32
0.45
0.63
Gain of 64
Gain of 128
0.041
0.055
0.086
0.118
0.144
0.283
0.397
0.593
0.64
1.04
1.55
2.3
2.95
4.89
11.76
11.33
0.6
0.29
0.38
0.54
0.74
0.92
1.49
4.02
3.07
0.1
0.13
0.18
0.23
0.29
0.48
0.88
0.99
0.039
0.057
0.087
0.124
0.153
0.265
0.379
0.568
0.96
1.45
2.13
2.85
4.74
9.5
9.44
Table 6. Typical Resolution (Bits) vs. Gain and Output Update Rate for the AD7798 Using a 2.5 V Reference
Update Rate
4.17 Hz
8.33 Hz
16.7 Hz
33.2 Hz
62 Hz
123 Hz
242 Hz
470 Hz
Gain of 1
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
Gain of 2
Gain of 4
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
16 (16)
Gain of 8
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
16 (16)
Gain of 16
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
Gain of 32
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
Gain of 64
Gain of 128
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
16 (14.5)
16 (14)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
16 (15.5)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
16 (15)
16 (14.5)
15.5 (13.5)
Rev. B | Page 10 of 28
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