AD7795 Analog Devices, AD7795 Datasheet - Page 13

• Manufacturer Part Number: AD7795
• Description: 6-Channel, Low Noise, Low Power, 16-Bit Sigma Delta ADC with On-Chip In-Amp and Reference
• Manufacturer: Analog Devices

Specifications of AD7795

• Resolution (bits): 16bit
• # Chan: 6
• Sample Rate: n/a
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref/PGA Gain) p-p
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

RMS NOISE AND RESOLUTION SPECIFICATIONS
The AD7794/AD7795 can be operated with chop enabled or
chop disabled, allowing the ADC to be optimized for switching
time or drift performance. With chop enabled, the settling time
is two times the conversion time. However, the offset is
continuously removed by the ADC leading to low offset and low
offset drift. With chop disabled, the allowable update rates are
the same as in chop enable mode. However, the settling time
now equals the conversion time. With chop disabled, the offset
is not removed by the ADC, so periodic offset calibrations can
be required to remove offset due to drift.
Table 5. RMS Noise (μV) vs. Gain and Output Update Rate Using an External 2.5 V Reference with Chop Enabled
Update Rate (Hz)
4.17
8.33
16.7
33.2
62
123
242
470
Table 6.
Effective Resolution (Bits) vs. Gain and Output Update Rate for the AD7794 Using an External 2.5 V Reference with Chop Enabled
Update Rate (Hz)
4.17
8.33
16.7
33.2
62
123
242
470
Table 7.
Effective Resolution (Bits) vs. Gain and Output Update Rate for the AD7795 Using an External 2.5 V Reference with Chop Enabled
Update Rate (Hz)
4.17
8.33
16.7
33.2
62
123
242
470
Gain of 1
0.64
1.04
1.55
2.3
2.95
4.89
11.76
11.33
Gain of 1
23 (20.5)
22 (19.5)
21.5 (19)
21 (18.5)
20.5 (18)
20 (17.5)
18.5 (16)
18.5 (16)
Gain of 1
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
Gain of 2
0.6
0.96
1.45
2.13
2.85
4.74
9.5
9.44
Gain of 2
22 (19.5)
21.5 (19)
20.5 (18)
20 (17.5)
19.5 (17)
19 (16.5)
18 (15.5)
18 (15.5)
Gain of 2
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
16 (15.5)
Gain of 4
0.29
0.38
0.54
0.74
0.92
1.49
4.02
3.07
Gain of 4
22 (19.5)
21.5 (19)
21 (18.5)
20.5 (18)
20.5 (18)
19.5 (17)
18 (15.5)
18.5 (16)
Gain of 4
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
16 (16)
Rev. D | Page 13 of 36
Gain of 8
Gain of 8
21.5 (19)
21 (18.5)
20.5 (18)
20 (17.5)
Gain of 8
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
16 (16)
0.22
0.26
0.36
0.5
0.58
1
1.96
1.79
20 (17.5)
19 (16.5)
18 (15.5)
18.5 (16)
CHOP ENABLED
External Reference
Table 5 shows the AD7794/AD7795 rms noise for some update
rates and gain settings. The numbers given are for the bipolar
input range with an external 2.5 V reference. These numbers are
typical and are generated with a differential input voltage of 0 V.
Table 6 and Table 7 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 are rounded to the nearest LSB.
Gain of 16
Gain of 16
Gain of 16
16 (15.5)
0.1
0.13
0.18
0.23
0.29
0.48
0.88
0.99
21.5 (19)
21 (18.5)
20.5 (18)
20.5 (18)
20 (17.5)
19.5 (17)
18.5 (16)
18 (15.5)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
Gain of 32
0.065
0.078
0.11
0.17
0.2
0.32
0.45
0.63
Gain of 32
21 (18.5)
21 (18.5)
20.5 (18)
20 (17.5)
19.5 (17)
19 (16.5)
18.5 (16)
18 (15.5)
Gain of 32
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
Gain of 64
0.039
0.057
0.087
0.124
0.153
0.265
0.379
0.568
Gain of 64
21 (18.5)
20.5 (18)
20 (17.5)
19 (16.5)
19 (16.5)
18 (15.5)
17.5 (15)
17 (14.5)
Gain of 64
16 (16)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
16 (15)
16 (14.5)
AD7794/AD7795
Gain of 128
Gain of 128
Gain of 128
0.041
0.055
0.086
0.118
0.144
0.283
0.397
0.593
20 (17.5)
19.5 (17)
19 (16.5)
18.5 (16)
18 (15.5)
17 (14.5)
16.5 (14)
16 (13.5)
16 (16)
16 (16)
16 (16)
16 (16)
16 (15.5)
16 (14.5)
16 (14)
16 (13.5)