Datasheet

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