AD7739 Analog Devices, AD7739 Datasheet - Page 10

• Manufacturer Part Number: AD7739
• Description: 8-Channel, 4 kHz, 24-Bit Sigma-Delta A/D Converter
• Manufacturer: Analog Devices

Specifications of AD7739

• Resolution (bits): 24bit
• # Chan: 8
• Sample Rate: 3.05MSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Bip,Diff-Uni,SE-Bip,SE-Uni
• Ain Range: Bip 0.625,Bip 1.25,Bip 2.5V,Uni 0.625,Uni 1.25,Uni 2.5V
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

AD7739
OUTPUT NOISE AND RESOLUTION SPECIFICATION
The AD7739 can be operated with chopping enabled or
disabled, allowing the ADC to be programmed to optimize
either the offset drift performance or the throughput rate and
channel switching time. Noise tables for these two primary
modes of operation are outlined below for a selection of output
rates and settling times.
The AD7739 noise performance depends on the selected
chopping mode, the filter word (FW) value, and the selected
analog input range. The AD7739 noise will not vary
significantly with MCLK frequency.
CHOPPING ENABLED
The first mode, in which the AD7739 is configured with
chopping enabled (CHOP = 1), provides very low noise with
lower output rates.
Table 4. Typical Output RMS Noise in µV vs. Conversion Time and Input Range with Chopping Enabled
FW
Table 5. Typical Effective Resolution in Bits vs. Conversion Time and Input Range with Chopping Enabled
FW
Table 6. Typical Peak-to-Peak Resolution in Bits vs. Conversion Time and Input Range with Chopping Enabled
FW
127
127
127
46
17
10
46
17
10
46
17
10
9
2
9
2
9
2
Conversion
Conversion
Conversion
Register
Register
Register
0xAE
0x8A
0xAE
0x8A
0xAE
0x8A
0x91
0x89
0x82
0x91
0x89
0x82
0xFF
0x91
0x89
0x82
0xFF
0xFF
Time
Time
Time
Conversion
Conversion
Conversion
2689
1001
2689
1001
2689
1001
Time
Time
Time
397
251
230
397
251
230
397
251
230
(µs)
(µs)
(µs)
84
84
84
Output Data
Output Data
Output Data
11838
11838
11838
2519
3982
4342
2519
3982
4342
2519
3982
4342
372
999
372
999
Rate
372
999
Rate
Rate
(Hz)
(Hz)
(Hz)
Frequency
Frequency
Frequency
1325
2209
2450
9500
1325
2209
2450
9500
1325
2209
2450
9500
Rev. 0 | Page 10 of 32
–3 dB
–3 dB
–3 dB
200
500
200
500
200
500
(Hz)
(Hz)
(Hz)
±2.5 V
±2.5 V
Table 4 to Table 6 show the –3 dB frequencies and typical
performance versus the channel conversion time and equivalent
output data rate, respectively.
Table 4 shows the typical output rms noise. Table 5 shows the
typical effective resolution based on rms noise. Table 6 shows
the typical output peak-to-peak resolution, representing values
for which there will be 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.
21.4
20.8
20.0
19.0
18.8
12.9
18.6
17.9
17.1
16.2
16.0
10.7
±2.5 V, +2.5 V
10.8
600
1.8
2.7
4.8
9.3
Input Range / Peak-to-Peak Resolution (Bits)
Input Range / Effective Resolution (Bits)
+2.5 V
+2.5 V
20.4
19.8
19.0
18.0
17.8
11.9
17.6
16.9
16.1
15.2
15.0
9.7
Input Range / RMS Noise (µV)
±1.25 V
±1.25 V
21.2
20.5
19.8
19.0
18.6
12.4
18.3
17.6
16.9
16.2
15.8
±1.25 V, +1.25 V, ±0.625 V, +0.625 V
9.7
+1.25 V ±0.625 V +0.625 V
+1.25 V ±0.625 V +0.625 V
20.2
19.5
18.8
18.0
17.6
11.4
17.3
16.6
15.9
15.2
14.8
8.7
460
1.1
1.7
2.7
4.7
6.3
20.2
19.5
18.8
18.0
17.6
11.4
17.3
16.6
15.9
15.2
14.8
8.7
19.2
18.5
17.8
17.0
16.6
10.4
16.3
15.6
14.9
14.2
13.8
7.7