AD7798/AD7799

Data Sheet

Rev. B | Page 10 of 28

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

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

0.29

0.22

0.1

0.065

0.039

0.041

8.33 Hz

1.04

0.96

0.38

0.26

0.13

0.078

0.057

0.055

16.7 Hz

1.55

1.45

0.54

0.36

0.18

0.11

0.087

0.086

33.2 Hz

2.3

2.13

0.74

0.5

0.23

0.17

0.124

0.118

62 Hz

2.95

2.85

0.92

0.58

0.29

0.2

0.153

0.144

123 Hz

4.89

4.74

1.49

1

0.48

0.32

0.265

0.283

242 Hz

11.76

9.5

4.02

1.96

0.88

0.45

0.379

0.397

470 Hz

11.33

9.44

3.07

1.79

0.99

0.63

0.568

0.593

Table 6. Typical Resolution (Bits) vs. Gain and Output Update Rate for the AD7798 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

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

8.33 Hz

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16.7 Hz

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

33.2 Hz

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

62 Hz

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (15.5)

123 Hz

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (16)

16 (15.5)

16 (14.5)

242 Hz

16 (16)

16 (15.5)

16 (15.5)

16 (15.5)

16 (16)

16 (16)

16 (15)

16 (14)

470 Hz

16 (16)

16 (15.5)

16 (16)

16 (16)

16 (15.5)

16 (15.5)

16 (14.5)

15.5 (13.5)