AD7195 Datasheet, PDF (41/44 Pages) Analog Devices – 4.8 kHz, Ultralow Noise, 24-Bit Sigma-Delta ADC with PGA and AC Excitation

AD7195
The 50 Hz/60 Hz rejection can be improved by setting the
REJ60 bit in the mode register to 1. With FS[9:0] set to 96 and
REJ60 set to 1, the filter response shown in Figure 49 is achieved.
The output data rate is unchanged, but the 50 Hz/60 Hz ± 1 Hz
rejection improves to 73 dB typically.
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
25
50
75
100
125
150
FREQUENCY (Hz)
Figure 49. Sinc³ Filter Response
(FS[9:0] = 96, Chop Enabled, REJ60 = 1)
SUMMARY OF FILTER OPTIONS
The AD7195 has several filter options. The filter that is chosen
affects the output data rate, settling time, the rms noise, the stop
band attenuation, and the 50 Hz/60 Hz rejection.
Table 35 shows some sample configurations and the corres-
ponding performance in terms of throughput, settling time and
50 Hz/60 Hz rejection.
Table 35. Filter Summary¹
Filter
Sinc⁴, Chop Disabled³
Sinc⁴, Chop Disabled
Sinc³, Chop Disabled
Sinc⁴, Chop Disabled
Sinc³, Chop Disabled
Sinc⁴, Chop Disabled
Sinc⁴, Chop Disabled
Sinc³, Chop Disabled
Sinc³, Chop Disabled
Sinc⁴, Chop Disabled
Sinc³, Chop Disabled
Sinc⁴, Chop Disabled, Zero
Latency
Sinc⁴, Chop Disabled, Zero
Latency
Sinc⁴, Chop Disabled, Zero
Latency
Sinc⁴, Chop Enabled
Sinc³, Chop Enabled
FS[9:0]
1
5
5
480
480
96
96
96
96
80
80
96
96
80
96
96
Output Data
Rate (Hz)
4800
960
960
10
10
50
50
50
50
60
60
12.5
12.5
15
12.5
16.7
Settling
Time (ms)
0.83
4.17
3.125
400
300
80
80
60
60
66.67
50
80
Throughput² (Hz)
1200
240
320
2.5
3.33
12.5
12.5
16.7
16.7
15
20
12.5
REJ60
0
0
0
0
0
0
1
0
1
0
0
0
50 Hz Rejection (dB)
No 50 Hz or 60 Hz rejection
No 50 Hz or 60 Hz rejection
No 50 Hz or 60 Hz rejection
120 dB ( 50 Hz and 60 Hz)
100 dB (50 Hz and 60 Hz)
120 dB (50 Hz only)
82 dB ( 50 Hz and 60 Hz)
95 dB (50 Hz only)
67 dB ( 50 Hz and 60 Hz)
120 dB (60 Hz only)
95 dB (60 Hz only)
120 dB (50 Hz only)
80
12.5
1
82 dB ( 50 Hz and 60 Hz)
66.67
15
0
120 dB (60 Hz only)
160
6.25
120
8.33
1
80 dB (50 Hz and 60 Hz)
1
67 dB (50 Hz and 60 Hz)
1 _{These calculations assume a 4.92 MHz stable master clock.}
2 _{Throughput is the rate at which conversions are available when several channels are enabled. In zero latency mode, the output data rate and throughput are equal.}
3 _{For output dates rates greater than 1 kHz, the sinc}4 _{filter is recommended.}
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