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)