AD7739

Data Sheet

Rev. A | Page 12 of 32

CHOPPING DISABLED

The second mode, in which the AD7739 is configured with

chopping disabled (chop = 0), provides faster conversion time

while maintaining high resolution. Table 8 to Table 10 show the

−3 dB frequencies and typical performance versus the channel

conversion time and equivalent output data rate, respectively.

Table 8 shows the typical output rms noise. Table 9 shows the

typical effective resolution based on the rms noise.

Table 10 shows the typical output peak-to-peak resolution,

representing values for which there is no code flicker within a

6-sigma limit. The peak-to-peak resolutions are not calculated

based on rms noise but on peak-to-peak noise.

These typical numbers are generated from 4096 data samples

acquired in continuous conversion mode with an analog input

voltage set to 0 V and MCLK = 6.144 MHz. The conversion

time is selected via the channel conversion time register.

Table 8. Typical Output RMS Noise in µV vs. Conversion Time and Input Range with Chopping Disabled

FW

Conversion

Time

Register

Conversion

Time (µs)

Output Data

Rate (Hz)

−3 dB

Frequency

(Hz)

Input Range/RMS Noise (µV)

±2.5 V, +2.5 V

±1.25 V, +1.25 V, ±0.625 V, +0.625 V

127

0x7F

1358

737

675

2.4

1.5

92

0x5C

993

1007

950

3.0

1.8

35

0x23

399

2504

2500

4.5

2.7

16

0x10

201

4963

5400

6.9

4.1

12

0x0C

160

6257

7250

9.6

5.3

11

0x0B

149

6693

7900

11.4

6.9

3

0x03

66

15133

29000

200

90

Table 9. Typical Effective Resolution in Bits vs. Conversion Time and Input Range with Chopping Disabled

FW

Conversion

Time

Register

Conversion

Time (µs)

Output Data

Rate (Hz)

−3 dB

Frequency

(Hz)

Input Range/Effective Resolution (Bits)

±2.5 V

+2.5 V

±1.25 V

+1.25 V ±0.625 V +0.625 V

127

0x7F

1358

737

675

21.0

20.0

20.6

19.6

19.6

18.6

92

0x5C

993

1007

950

20.7

19.7

20.4

19.4

19.4

18.4

35

0x23

399

2504

2500

20.1

19.1

19.8

18.8

18.8

17.8

16

0x10

201

4963

5400

19.4

18.4

19.2

18.2

18.2

17.2

12

0x0C

160

6257

7250

18.9

17.9

18.8

17.8

17.8

16.8

11

0x0B

149

6693

7900

18.8

17.8

18.5

17.5

17.5

16.5

3

0x03

66

15133

29000

14.6

13.6

14.7

13.7

13.7

12.7

Table 10. Typical Peak-to-Peak Resolution in Bits vs. Conversion Time and Input Range with Chopping Disabled

FW

Conversion

Time

Register

Conversion

Time (µs)

Output Data

Rate (Hz)

−3 dB

Frequency

(Hz)

Input Range/Peak-to-Peak Resolution (Bits)

±2.5 V

+2.5 V

±1.25 V

+1.25 V ±0.625 V +0.625 V

127

0x7F

1358

737

675

18.2

17.2

17.8

16.8

16.8

15.8

92

0x5C

993

1007

950

17.8

16.8

17.6

16.6

16.6

15.6

35

0x23

399

2504

2500

17.2

16.2

17.0

16.0

16.0

15.0

16

0x10

201

4963

5400

16.6

15.6

16.4

15.4

15.4

14.4

12

0x0C

160

6257

7250

16.1

15.1

16.0

15.0

15.0

14.0

11

0x0B

149

6693

7900

16.0

15.0

15.7

14.7

14.7

13.7

3

0x03

66

15133

29000

11.7

10.7

12.0

11.0

11.0

10.0