AD7785_15 Datasheet, PDF (11/32 Pages) Analog Devices – 3-Channel, Low Noise, Low Power

AD7785
OUTPUT NOISE AND RESOLUTION SPECIFICATIONS
EXTERNAL REFERENCE
Table 5 shows the output rms noise of the AD7785 for some of
the update rates and gain settings. The numbers given are for
the bipolar input range with an external 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, with the
output peak-to-peak (p-p) resolution shown in parentheses. It is
important to note that the effective resolution is calculated
using the rms noise, while the p-p resolution is based on the p-p
noise. The p-p 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 Using an External 2.5 V Reference
Update Rate (Hz) Gain of 1 Gain of 2 Gain of 4 Gain of 8 Gain of 16 Gain of 32
4.17
0.64
0.6
0.29
0.22
0.1
0.065
8.33
1.04
0.96
0.38
0.26
0.13
0.078
16.7
1.55
1.45
0.54
0.36
0.18
0.11
33.2
2.3
2.13
0.74
0.5
0.23
0.17
62
2.95
2.85
0.92
0.58
0.29
0.2
123
4.89
4.74
1.49
1
0.48
0.32
242
11.76
9.5
4.02
1.96
0.88
0.45
470
11.33
9.44
3.07
1.79
0.99
0.63
Gain of 64
0.039
0.057
0.087
0.124
0.153
0.265
0.379
0.568
Gain of 128
0.041
0.055
0.086
0.118
0.144
0.283
0.397
0.593
Table 6. Typical Resolution (Bits) vs. Gain and Output Update Rate Using an External 2.5 V Reference
Update Rate (Hz) Gain of 1 Gain of 2 Gain of 4 Gain of 8 Gain of 16 Gain of 32 Gain of 64
4.17
20 (20)
20 (19.5) 20 (19.5) 20 (19)
20 (19)
20 (18.5)
20 (18.5)
8.33
20 (19.5) 20 (19)
20 (19)
20 (18.5) 20 (18.5)
20 (18.5)
20 (18)
16.7
20 (19)
20 (18)
20 (18.5) 20 (18)
20 (18)
20 (18)
20 (17.5)
33.2
20 (18.5) 20 (17.5) 20 (18)
20 (17.5) 20 (18)
20 (17.5)
19 (16.5)
62
20 (18)
19.5 (17) 20 (18)
20 (17.5) 20 (17.5)
19.5 (17)
19 (16.5)
123
20 (17.5) 19 (16.5) 19.5 (17) 19 (16.5) 19.5 (17)
19 (16.5)
18 (15.5)
242
18.5 (16) 18 (15.5) 18 (15.5) 18 (15.5) 18.5 (16)
18.5 (16)
17.5 (15)
470
18.5 (16) 18 (15.5) 18.5 (16) 18.5 (16) 18 (15.5)
18 (15.5)
17 (14.5)
Gain of 128
20 (17.5)
19.5 (17)
19 (16.5)
18.5 (16)
18 (15.5)
17 (14.5)
16.5 (14)
16 (13.5)
Rev. 0 | Page 11 of 32