7.1 Noise Measurements
The ADS1291, ADS1292, and ADS1292R noise performance can be optimized by adjusting the data rate and PGA setting. As the averaging is increased by reducing the data rate, the noise drops correspondingly. Increasing the programmable gain amplifier (PGA) value reduces the input-referred noise, which is particularly useful when measuring low-level biopotential signals. Table 1 through Table 8 summarize the ADS1291, ADS1292, and ADS1292R noise performance. The data are representative of typical noise performance at TA = +25°C. The data shown are the result of averaging the readings from multiple devices and are measured with the inputs shorted together. For the shown data rates, the ratio is approximately 6.6.
Table 1 through Table 8 show measurements taken with an internal reference. The data are also representative of the ADS1291, ADS1292, and ADS1292R noise performance when using a low-noise external reference such as the REF5025.
In Table 1 through Table 8, µVRMS and µVPP are measured values. Effective resolution (EFF RESOL) and dynamic range (DYN RANGE) are calculated with Equation 1 and Equation 2.
Equation 1.
Equation 2.
Table 1. Input-Referred Noise (μVRMS / μVPP) 3-V Analog Supply and 2.42-V Reference(1)
DR BITS OF CONFIG1 REGISTER |
OUTPUT DATA RATE (SPS) |
–3-dB BANDWIDTH (Hz) |
PGA GAIN = 1 |
PGA GAIN = 2 |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
000 |
125 |
32.75 |
1.5 |
10.3 |
121.0 |
18.83 |
20.10 |
0.8 |
5.6 |
120.0 |
18.71 |
19.94 |
001 |
250 |
65.5 |
2.2 |
14.4 |
117.8 |
18.34 |
19.58 |
1.2 |
7.5 |
117.1 |
18.29 |
19.46 |
010 |
500 |
131 |
3.0 |
18.9 |
115.1 |
17.95 |
19.11 |
1.7 |
10.9 |
113.9 |
17.75 |
18.91 |
011 |
1000 |
262 |
4.6 |
30.8 |
111.3 |
17.25 |
18.49 |
2.5 |
15.6 |
110.6 |
17.23 |
18.37 |
100 |
2000 |
524 |
10.1 |
99 |
104.5 |
15.57 |
17.36 |
5.3 |
48 |
104.0 |
15.60 |
17.28 |
101 |
4000 |
1048 |
55.2 |
563 |
89.7 |
13.06 |
14.91 |
26.0 |
265 |
90.3 |
13.14 |
15.00 |
110 |
8000 |
2096 |
287.3 |
2930 |
75.4 |
10.68 |
12.53 |
144.1 |
1470 |
75.4 |
10.67 |
12.52 |
111 |
NA |
NA |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
(1) At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.
Table 2. Input-Referred Noise (μVRMS / μVPP) 3-V Analog Supply and 2.42-V Reference(1)
DR BITS OF CONFIG1 REGISTER |
OUTPUT DATA RATE (SPS) |
–3-dB BANDWIDTH (Hz) |
PGA GAIN = 3 |
PGA GAIN = 4 |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
000 |
125 |
32.75 |
0.6 |
4.1 |
119.2 |
18.58 |
19.80 |
0.5 |
3.4 |
117.9 |
18.42 |
19.58 |
001 |
250 |
65.5 |
0.9 |
5.5 |
115.9 |
18.15 |
19.26 |
0.8 |
5.0 |
114.8 |
17.88 |
19.07 |
010 |
500 |
131 |
1.3 |
7.7 |
113.0 |
17.67 |
18.77 |
1.1 |
6.6 |
111.9 |
17.47 |
18.59 |
011 |
1000 |
262 |
1.9 |
12.0 |
109.5 |
17.02 |
18.19 |
1.6 |
10.3 |
108.7 |
16.83 |
18.06 |
100 |
2000 |
524 |
3.7 |
31 |
103.7 |
15.65 |
17.23 |
2.9 |
23 |
103.2 |
15.69 |
17.14 |
101 |
4000 |
1048 |
17.0 |
173 |
90.5 |
13.18 |
15.03 |
12.2 |
124 |
90.8 |
13.24 |
15.09 |
110 |
8000 |
2096 |
91.9 |
937 |
75.8 |
10.74 |
12.59 |
66.8 |
681 |
76.1 |
10.78 |
12.63 |
111 |
NA |
NA |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
(1) At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.
Table 3. Input-Referred Noise (μVRMS / μVPP) 3-V Analog Supply and 2.42-V Reference(1)
DR BITS OF CONFIG1 REGISTER |
OUTPUT DATA RATE (SPS) |
–3-dB BANDWIDTH (Hz) |
PGA GAIN = 6 |
PGA GAIN = 8 |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
000 |
125 |
32.75 |
0.5 |
3.0 |
115.9 |
18.04 |
19.26 |
0.4 |
2.6 |
114.0 |
17.82 |
18.94 |
001 |
250 |
65.5 |
0.7 |
4.1 |
112.8 |
17.58 |
18.73 |
0.6 |
3.9 |
111.0 |
17.22 |
18.44 |
010 |
500 |
131 |
0.9 |
5.6 |
109.9 |
17.14 |
18.25 |
0.8 |
5.5 |
108.0 |
16.75 |
17.93 |
011 |
1000 |
262 |
1.3 |
8.7 |
106.8 |
16.49 |
17.73 |
1.2 |
7.6 |
104.9 |
16.26 |
17.42 |
100 |
2000 |
524 |
2.2 |
16 |
102.1 |
15.64 |
16.96 |
2.0 |
14 |
100.7 |
15.36 |
16.72 |
101 |
4000 |
1048 |
7.5 |
77 |
91.5 |
13.34 |
15.19 |
5.5 |
56 |
91.7 |
13.39 |
15.24 |
110 |
8000 |
2096 |
42.7 |
436 |
76.4 |
10.84 |
12.69 |
31.3 |
319 |
76.6 |
10.88 |
12.73 |
111 |
NA |
NA |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
(1) At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.
Table 4. Input-Referred Noise (μVRMS / μVPP) 3-V Analog Supply and 2.42-V Reference(1)
DR BITS OF CONFIG1 REGISTER |
OUTPUT DATA RATE (SPS) |
–3-dB BANDWIDTH (Hz) |
PGA GAIN = 12 |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
000 |
125 |
32.75 |
0.4 |
2.5 |
111.3 |
17.31 |
18.48 |
001 |
250 |
65.5 |
0.5 |
3.5 |
108.4 |
16.81 |
18.01 |
010 |
500 |
131 |
0.8 |
5.0 |
105.0 |
16.29 |
17.44 |
011 |
1000 |
262 |
1.1 |
6.9 |
102.1 |
15.82 |
16.97 |
100 |
2000 |
524 |
1.7 |
11 |
98.6 |
15.21 |
16.38 |
101 |
4000 |
1048 |
3.5 |
36 |
92.0 |
13.44 |
15.29 |
110 |
8000 |
2096 |
20.1 |
205 |
76.9 |
10.93 |
12.78 |
111 |
NA |
NA |
— |
— |
— |
— |
— |
(1) At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.
Table 5. Input-Referred Noise (μVRMS / μVPP) 5-V Analog Supply and 4.033-V Reference(1)
DR BITS OF CONFIG1 REGISTER |
OUTPUT DATA RATE (SPS) |
–3-dB BANDWIDTH (Hz) |
PGA GAIN = 1 |
PGA GAIN = 2 |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
000 |
125 |
32.75 |
1.6 |
10.2 |
124.9 |
19.58 |
20.75 |
0.9 |
5.4 |
124.3 |
19.50 |
20.65 |
001 |
250 |
65.5 |
2.2 |
13.3 |
122.3 |
19.20 |
20.31 |
1.2 |
8.1 |
121.3 |
18.91 |
20.15 |
010 |
500 |
131 |
3.1 |
18.9 |
119.3 |
18.69 |
19.82 |
1.7 |
10.6 |
118.2 |
18.52 |
19.63 |
011 |
1000 |
262 |
4.9 |
31.9 |
115.2 |
17.94 |
19.14 |
2.7 |
17.9 |
114.4 |
17.77 |
19.00 |
100 |
2000 |
524 |
15.5 |
167 |
105.2 |
15.55 |
17.48 |
7.5 |
80 |
105.5 |
15.62 |
17.53 |
101 |
4000 |
1048 |
89.6 |
959 |
90.0 |
13.03 |
14.95 |
45.0 |
481 |
89.9 |
13.02 |
14.94 |
110 |
8000 |
2096 |
460.1 |
4923 |
75.8 |
10.67 |
12.59 |
229.0 |
2450 |
75.8 |
10.67 |
12.59 |
111 |
NA |
NA |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
(1) At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.
Table 6. Input-Referred Noise (μVRMS / μVPP) 5-V Analog Supply and 4.033-V Reference(1)
DR BITS OF CONFIG1 REGISTER |
OUTPUT DATA RATE (SPS) |
–3-dB BANDWIDTH (Hz) |
PGA GAIN = 3 |
PGA GAIN = 4 |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
000 |
125 |
32.75 |
0.6 |
4.2 |
123.4 |
19.28 |
20.50 |
0.5 |
3.6 |
122.3 |
19.08 |
20.32 |
001 |
250 |
65.5 |
0.9 |
5.7 |
120.7 |
18.82 |
20.04 |
0.7 |
4.8 |
119.5 |
18.66 |
19.86 |
010 |
500 |
131 |
1.3 |
8.4 |
117.3 |
18.27 |
19.49 |
1.1 |
7.4 |
116.2 |
18.04 |
19.31 |
011 |
1000 |
262 |
2.0 |
13.3 |
113.5 |
17.62 |
18.85 |
1.6 |
11.0 |
112.7 |
17.48 |
18.72 |
100 |
2000 |
524 |
5.1 |
53 |
105.3 |
15.61 |
17.49 |
3.9 |
38 |
105.2 |
15.67 |
17.47 |
101 |
4000 |
1048 |
28.7 |
307 |
90.3 |
13.08 |
15.00 |
20.7 |
222 |
90.6 |
13.14 |
15.06 |
110 |
8000 |
2096 |
149.3 |
1598 |
76.0 |
10.70 |
12.62 |
111.8 |
1196 |
76.0 |
10.71 |
12.63 |
111 |
NA |
NA |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
(1) At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.
Table 7. Input-Referred Noise (μVRMS / μVPP) 5-V Analog Supply and 4.033-V Reference(1)
DR BITS OF CONFIG1 REGISTER |
OUTPUT DATA RATE (SPS) |
–3-dB BANDWIDTH (Hz) |
PGA GAIN = 6 |
PGA GAIN = 8 |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
000 |
125 |
32.75 |
0.5 |
3.0 |
120.4 |
18.78 |
19.99 |
0.4 |
2.7 |
118.5 |
18.48 |
19.68 |
001 |
250 |
65.5 |
0.6 |
4.0 |
117.5 |
18.36 |
19.52 |
0.6 |
3.8 |
115.7 |
18.01 |
19.21 |
010 |
500 |
131 |
0.9 |
6.0 |
114.3 |
17.75 |
18.99 |
0.8 |
5.3 |
112.8 |
17.53 |
18.74 |
011 |
1000 |
262 |
1.4 |
8.8 |
110.8 |
17.20 |
18.41 |
1.2 |
8.1 |
109.5 |
16.92 |
18.19 |
100 |
2000 |
524 |
2.8 |
24 |
104.6 |
15.74 |
17.38 |
2.3 |
18 |
103.6 |
15.73 |
17.22 |
101 |
4000 |
1048 |
13.3 |
142 |
91.0 |
13.20 |
15.12 |
9.3 |
100 |
91.5 |
13.29 |
15.21 |
110 |
8000 |
2096 |
71.5 |
765 |
76.4 |
10.77 |
12.69 |
52.3 |
560 |
76.6 |
10.80 |
12.72 |
111 |
NA |
NA |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
(1) At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.
Table 8. Input-Referred Noise (μVRMS / μVPP) 5-V Analog Supply and 4.033-V Reference(1)
DR BITS OF CONFIG1 REGISTER |
OUTPUT DATA RATE (SPS) |
–3-dB BANDWIDTH (Hz) |
PGA GAIN = 12 |
μVRMS |
μVPP |
DYN RANGE |
EFF RESOL |
ENOB |
000 |
125 |
32.75 |
0.4 |
2.6 |
115.7 |
17.96 |
19.21 |
001 |
250 |
65.5 |
0.5 |
3.4 |
112.9 |
17.59 |
18.75 |
010 |
500 |
131 |
0.8 |
5.2 |
109.8 |
16.96 |
18.24 |
011 |
1000 |
262 |
1.1 |
6.9 |
106.6 |
16.56 |
17.70 |
100 |
2000 |
524 |
1.9 |
14 |
101.9 |
15.57 |
16.83 |
101 |
4000 |
1048 |
5.9 |
63 |
92.0 |
13.37 |
15.29 |
110 |
8000 |
2096 |
33.8 |
362 |
76.9 |
10.85 |
12.77 |
111 |
NA |
NA |
— |
— |
— |
— |
— |
(1) At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.