Datasheet
Data Sheet AD7798/AD7799
Rev. B | Page 11 of 28
AD7799
Table 7 shows the AD7799 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 8
shows the effective resolution, and the output peak-to-peak
resolution is given in parentheses. Note that the effective
resolution is calculated using the rms noise, whereas the
peak-to-peak resolution is based on 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 7. Output RMS Noise (µV) vs. Gain and Output Update Rate for the AD7799 Using a 2.5 V Reference
Update Rate Gain of 1 Gain of 2 Gain of 4 Gain of 8 Gain of 16 Gain of 32 Gain of 64 Gain of 128
4.17 Hz 0.64 0.6 0.185 0.097 0.075 0.035 0.027 0.027
8.33 Hz 1.04 0.96 0.269 0.165 0.108 0.048 0.037 0.040
16.7 Hz 1.55 1.45 0.433 0.258 0.176 0.085 0.065 0.065
33.2 Hz 2.3 2.13 0.647 0.364 0.24 0.118 0.097 0.094
62 Hz 2.95 2.85 0.952 0.586 0.361 0.178 0.133 0.134
123 Hz 4.89 4.74 1.356 0.785 0.521 0.265 0.192 0.192
242 Hz 11.76 9.5 3.797 2.054 1.027 0.476 0.326 0.308
470 Hz 11.33 9.44 3.132 1.773 1.107 0.5 0.413 0.374
Table 8. Typical Resolution (Bits) vs. Gain and Output Update Rate for the AD7799 Using a 2.5 V Reference
Update Rate Gain of 1 Gain of 2 Gain of 4 Gain of 8 Gain of 16 Gain of 32 Gain of 64 Gain of 128
4.17 Hz 23 (20.5) 22 (19.5) 22.5 (20) 22.5 (20) 22 (19.5) 22 (19.5) 21.5 (19) 20.5 (18)
8.33 Hz 22 (19.5) 21.5 (19) 22 (19.5) 22 (19.5) 21.5 (19) 21.5 (19) 21 (18.5) 20 (17.5)
16.7 Hz 21.5 (19) 20.5 (18) 21.5 (19) 21 (18.5) 21 (18.5) 21 (18.5) 20 (17.5) 19 (16.5)
33.3 Hz
21 (18.5)
20 (17.5)
21 (18.5)
20.5 (18)
20.5 (18)
20.5 (18)
19.5 (17)
18.5 (16)
62 Hz 20.5 (18) 19.5 (17) 20.5 (18) 20 (17.5) 19.5 (17) 19.5 (17) 19 (16.5) 18 (15.5)
123 Hz 20 (17.5) 19 (16.5) 20 (17.5) 19.5 (17) 19 (16.5) 19 (16.5) 18.5 (16) 17.5 (15)
242 Hz 18.5 (16) 18 (15.5) 18.5 (16) 18 (15.5) 18 (15.5) 18.5 (16) 18 (15.5) 17 (14.5)
470 Hz 18.5 (16) 18 (15.5) 18.5 (16) 18.5 (16) 18 (15.5) 18.5 (16) 17.5 (15) 16.5 (14)