Datasheet

AD7794/AD7795
Rev. D | Page 14 of 36
Internal Reference
Table 8 shows the AD7794/AD7795 rms noise for some of the
update rates and gain settings. The numbers given are for the
bipolar input range with the internal 1.17 V reference. These
numbers are typical and are generated with a differential input
voltage of 0 V.
Table 9 and Table 10 show the effective resolution
while the output peak-to-peak (p-p) resolution is listed in brackets.
It is important to note that the effective resolution is calculated
using the rms noise while the p-p resolution is calculated based
on peak-to-peak noise. The p-p resolution represents the
resolution for which there is no code flicker. These numbers are
typical and rounded to the nearest LSB.
Table 8. RMS Noise (μV) vs. Gain and Output Update Rate Using an Internal 1.17 V Reference with Chop Enabled
Update Rate (Hz) 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 0.81 0.67 0.32 0.2 0.13 0.065 0.04 0.039
8.33 1.18 1.11 0.41 0.25 0.16 0.078 0.058 0.059
16.7 1.96 1.72 0.55 0.36 0.25 0.11 0.088 0.088
33.2 2.99 2.48 0.83 0.48 0.33 0.17 0.13 0.12
62 3.6 3.25 1.03 0.65 0.46 0.2 0.15 0.15
123 5.83 5.01 1.69 0.96 0.67 0.32 0.25 0.26
242 11.22 8.64 2.69 1.9 1.04 0.45 0.35 0.34
470 12.46 10.58 4.58 2 1.27 0.63 0.50 0.49
Table 9.
Effective Resolution (Bits) vs. Gain and Output Update Rate for the AD7794 Using an Internal 1.17 V Reference with Chop Enabled
Update Rate (Hz) 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 21.5 (19) 20.5 (18) 21 (18.5) 20.5 (18) 20 (17.5) 20 (17.5) 20 (17.5) 19 (16.5)
8.33 21 (18.5) 20 (17.5) 20.5 (18) 20 (17.5) 20 (17.5) 20 (17.5) 19 (16.5) 18 (15.5)
16.7 20 (17.5) 19.5 (17) 20 (17.5) 19.5 (17) 19 (16.5) 19.5 (17) 18.5 (16) 17.5 (15)
33.2 19.5 (17) 19 (16.5) 19.5 (17) 19 (16.5) 19 (16.5) 18.5 (16) 18 (15.5) 17 (14.5)
62 19.5 (17) 18.5 (16) 19 (16.5) 19 (16.5) 18.5 (16) 18.5 (16) 18 (15.5) 17 (14.5)
123 18.5 (16) 18 (15.5) 18.5 (16) 18 (15.5) 17.5 (15) 18 (15.5) 17 (14.5) 16 (13.5)
242 17.5 (15) 17 (14.5) 17.5 (15) 17 (14.5) 17 (14.5) 17.5 (15) 16.5 (14) 15.5 (13)
470 17.5 (15) 17 (14.5) 17 (14.5) 17 (14.5) 17 (14.5) 17 (14.5) 16 (13.5) 15 (12.5)
Table 10.
Effective Resolution (Bits) vs. Gain and Output Update Rate for the AD7795 Using an Internal 1.17 V Reference with Chop Enabled
Update Rate (Hz) 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 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (16)
8.33 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (15.5)
16.7 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (15)
33.2 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (15.5) 16 (14.5)
62 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (16) 16 (15.5) 16 (14.5)
123 16 (16) 16 (15.5) 16 (16) 16 (15.5) 16 (15) 16 (15.5) 16 (14.5) 16 (13.5)
242 16 (15) 16 (14.5) 16 (15) 16 (14.5) 16 (14.5) 16 (15) 16 (14) 15.5 (13)
470 16 (15) 16 (14.5) 16 (14.5) 16 (14.5) 16 (14.5) 16 (14.5) 16 (13.5) 15 (12.5)