8.1 Noise Measurements
Adjust the data rate and gain to optimize the ADS131A02 and ADS131A04 noise performance. When averaging is increased by reducing the data rate, noise drops correspondingly. Table 1 and Table 2 summarize the ADS131A0x noise performance with a 2.442-V reference and a 3.3-V analog power supply. Table 3 and Table 4 summarize the ADS131A02 and ADS131A04 noise performance with a 4.0-V reference and a 5-V analog power supply (or using ±2.5-V bipolar analog power supplies). The data are representative of typical noise performance at TA = 25°C when fMOD = 4.096 MHz. The data shown are typical results with the analog inputs shorted together and taking an average of multiple readings across all channels. A minimum 1 second of consecutive readings are used to calculate the RMS noise for each reading. The data are also representative of the ADS131A0x noise performance when using a low-noise external reference, such as the REF5025 or REF5040. The effective resolution data and dynamic range data in Table 1, Table 2, Table 3, and Table 4 are calculated using Equation 1 and Equation 2. The μVrms noise numbers in the tables are input-referred.
Equation 1.
Equation 2.
Table 1. Dynamic Range, Effective Resolution, and Noise in μVrms at 3.3-V Analog Supply, and 2.442-V Reference for Gain = 1, 2, and 4
OSR SETTING |
fDATA AT 4.096-MHz fMOD (kHz) |
GAIN |
x1 |
x2 |
x4 |
DYNAMIC RANGE (dB) |
EFFECTIVE RESOLUTION (Bits) |
μVrms
|
DYNAMIC RANGE (dB) |
EFFECTIVE RESOLUTION (Bits) |
μVrms
|
DYNAMIC RANGE (dB) |
EFFECTIVE RESOLUTION (Bits) |
μVrms
|
4096 |
1.000 |
119.49 |
21.35 |
1.82 |
113.49 |
20.35 |
1.82 |
108.08 |
19.46 |
1.70 |
2048 |
2.000 |
116.47 |
20.85 |
2.58 |
110.97 |
19.94 |
2.44 |
105.22 |
18.98 |
2.36 |
1024 |
4.000 |
113.85 |
20.41 |
3.49 |
107.91 |
19.43 |
3.47 |
101.77 |
18.41 |
3.52 |
800 |
5.120 |
112.93 |
20.26 |
3.88 |
106.72 |
19.23 |
3.98 |
101.05 |
18.29 |
3.82 |
768 |
5.333 |
112.90 |
20.25 |
3.90 |
106.69 |
19.22 |
3.99 |
100.76 |
18.24 |
3.95 |
512 |
8.000 |
110.73 |
19.89 |
5.01 |
104.83 |
18.91 |
4.95 |
98.75 |
17.91 |
4.97 |
400 |
10.240 |
109.74 |
19.73 |
5.61 |
103.69 |
18.72 |
5.64 |
97.76 |
17.74 |
5.58 |
384 |
10.667 |
109.53 |
19.70 |
5.75 |
103.65 |
18.72 |
5.66 |
97.58 |
17.71 |
5.69 |
256 |
16.000 |
107.74 |
19.40 |
7.07 |
101.67 |
18.39 |
7.11 |
95.72 |
17.40 |
7.06 |
200 |
20.480 |
106.48 |
19.19 |
8.17 |
100.55 |
18.20 |
8.09 |
94.54 |
17.21 |
8.08 |
192 |
21.333 |
106.28 |
19.16 |
8.36 |
100.17 |
18.14 |
8.45 |
94.11 |
17.13 |
8.49 |
128 |
32.000 |
104.05 |
18.78 |
10.81 |
97.98 |
17.78 |
10.88 |
92.00 |
16.78 |
10.82 |
96 |
42.667 |
101.90 |
18.43 |
13.85 |
95.95 |
17.44 |
13.74 |
89.90 |
16.43 |
13.79 |
64 |
64.000 |
97.63 |
17.72 |
22.64 |
91.61 |
16.72 |
22.64 |
85.52 |
15.71 |
22.83 |
48 |
85.333 |
92.58 |
16.88 |
40.50 |
86.62 |
15.89 |
40.22 |
80.59 |
14.89 |
40.26 |
32 |
128.000 |
85.12 |
15.62 |
96.82 |
78.96 |
14.62 |
97.12 |
73.02 |
13.61 |
97.51 |
Table 2. Dynamic Range, Effective Resolution, and Noise in μVrms at 3.3-V Analog Supply, and 2.442-V Reference for Gain = 8 and 16
OSR SETTING |
fDATA AT 4.096-MHz fMOD (kHz) |
GAIN |
x8 |
x16 |
DYNAMIC RANGE (dB) |
EFFECTIVE RESOLUTION (Bits) |
μVrms
|
DYNAMIC RANGE (dB) |
EFFECTIVE RESOLUTION (Bits) |
μVrms
|
4096 |
1.000 |
101.72 |
18.40 |
1.77 |
95.45 |
17.36 |
1.82 |
2048 |
2.000 |
98.88 |
17.93 |
2.45 |
93.07 |
16.96 |
2.39 |
1024 |
4.000 |
95.97 |
17.44 |
3.43 |
89.82 |
16.42 |
3.48 |
800 |
5.120 |
95.03 |
17.29 |
3.82 |
88.66 |
16.23 |
3.98 |
768 |
5.333 |
94.63 |
17.22 |
4.00 |
88.41 |
16.19 |
4.09 |
512 |
8.000 |
92.75 |
16.91 |
4.96 |
87.00 |
15.95 |
4.81 |
400 |
10.240 |
91.84 |
16.76 |
5.51 |
85.62 |
15.72 |
5.64 |
384 |
10.667 |
91.52 |
16.70 |
5.72 |
85.50 |
15.70 |
5.72 |
256 |
16.000 |
89.57 |
16.38 |
7.16 |
83.58 |
15.38 |
7.14 |
200 |
20.480 |
88.44 |
16.19 |
8.16 |
82.45 |
15.20 |
8.12 |
192 |
21.333 |
88.26 |
16.16 |
8.32 |
82.12 |
15.14 |
8.44 |
128 |
32.000 |
86.02 |
15.79 |
10.77 |
79.80 |
14.76 |
11.02 |
96 |
42.667 |
83.91 |
15.44 |
13.74 |
77.72 |
14.41 |
14.00 |
64 |
64.000 |
79.52 |
14.71 |
22.78 |
73.45 |
13.70 |
22.92 |
48 |
85.333 |
74.60 |
13.89 |
40.14 |
68.47 |
12.87 |
40.66 |
32 |
128.000 |
66.93 |
12.62 |
97.05 |
60.97 |
11.61 |
97.61 |
Table 3. Dynamic Range, Effective Resolution, and Noise in μVrms at ±2.5-V Analog Supply, and 4.0-V Reference for Gain = 1, 2, and 4
OSR SETTING |
fDATA AT 4.096-MHz fMOD (kHz) |
GAIN |
x1 |
x2 |
x4 |
DYNAMIC RANGE (dB) |
EFFECTIVE RESOLUTION (Bits) |
μVrms
|
DYNAMIC RANGE (dB) |
EFFECTIVE RESOLUTION (Bits) |
μVrms
|
DYNAMIC RANGE (dB) |
EFFECTIVE RESOLUTION (Bits) |
μVrms
|
4096 |
1.000 |
124.55 |
22.19 |
1.66 |
118.69 |
21.22 |
1.64 |
112.32 |
20.16 |
1.71 |
2048 |
2.000 |
121.47 |
21.68 |
2.38 |
114.98 |
20.60 |
2.51 |
109.58 |
19.70 |
2.34 |
1024 |
4.000 |
118.44 |
21.18 |
3.37 |
112.48 |
20.18 |
3.36 |
106.31 |
19.16 |
3.41 |
800 |
5.120 |
117.58 |
21.03 |
3.72 |
111.46 |
20.02 |
3.77 |
105.29 |
18.99 |
3.84 |
768 |
5.333 |
116.75 |
20.89 |
4.10 |
110.88 |
19.92 |
4.03 |
105.06 |
18.95 |
3.94 |
512 |
8.000 |
115.16 |
20.63 |
4.93 |
109.23 |
19.65 |
4.88 |
103.10 |
18.63 |
4.94 |
400 |
10.240 |
114.15 |
20.46 |
5.53 |
108.33 |
19.50 |
5.41 |
102.28 |
18.49 |
5.43 |
384 |
10.667 |
113.88 |
20.42 |
5.71 |
107.83 |
19.41 |
5.73 |
101.70 |
18.39 |
5.80 |
256 |
16.000 |
112.09 |
20.12 |
7.02 |
105.76 |
19.07 |
7.27 |
99.83 |
18.08 |
7.19 |
200 |
20.480 |
110.71 |
19.89 |
8.22 |
104.65 |
18.88 |
8.27 |
98.37 |
17.84 |
8.51 |
192 |
21.333 |
110.13 |
19.79 |
8.79 |
104.10 |
18.79 |
8.80 |
97.99 |
17.78 |
8.90 |
128 |
32.000 |
106.93 |
19.26 |
12.72 |
100.76 |
18.24 |
12.94 |
94.59 |
17.21 |
13.15 |
96 |
42.667 |
104.17 |
18.80 |
17.47 |
98.18 |
17.81 |
17.41 |
92.00 |
16.78 |
17.74 |
64 |
64.000 |
98.84 |
17.92 |
32.27 |
92.74 |
16.91 |
32.58 |
86.50 |
15.87 |
33.40 |
48 |
85.333 |
93.30 |
17.00 |
61.06 |
87.45 |
16.03 |
59.91 |
81.31 |
15.01 |
60.74 |
32 |
128.000 |
85.10 |
15.64 |
156.92 |
78.87 |
14.60 |
160.84 |
73.35 |
13.67 |
153.69 |
Table 4. Dynamic Range, Effective Resolution, and Noise in μVrms at ±2.5-V Analog Supply, and 4.0-V Reference for Gain = 8 and 16
OSR SETTING |
fDATA AT 4.096-MHz fMOD (kHz) |
GAIN |
x8 |
x16 |
DYNAMIC RANGE (dB) |
EFFECTIVE RESOLUTION (Bits) |
μVrms
|
DYNAMIC RANGE (dB) |
EFFECTIVE RESOLUTION (Bits) |
μVrms
|
4096 |
1.000 |
106.35 |
19.17 |
1.70 |
100.66 |
18.22 |
1.63 |
2048 |
2.000 |
103.40 |
18.68 |
2.38 |
97.37 |
17.68 |
2.39 |
1024 |
4.000 |
100.46 |
18.19 |
3.35 |
94.59 |
17.21 |
3.29 |
800 |
5.120 |
99.53 |
18.04 |
3.72 |
93.28 |
17.00 |
3.83 |
768 |
5.333 |
99.19 |
17.98 |
3.87 |
93.09 |
16.97 |
3.91 |
512 |
8.000 |
97.31 |
17.67 |
4.81 |
91.08 |
16.63 |
4.93 |
400 |
10.240 |
96.23 |
17.49 |
5.45 |
90.16 |
16.48 |
5.48 |
384 |
10.667 |
95.84 |
17.42 |
5.70 |
89.85 |
16.43 |
5.68 |
256 |
16.000 |
93.87 |
17.09 |
7.15 |
87.73 |
16.07 |
7.25 |
200 |
20.480 |
92.70 |
16.90 |
8.18 |
86.43 |
15.86 |
8.41 |
192 |
21.333 |
92.10 |
16.80 |
8.77 |
85.68 |
15.73 |
9.17 |
128 |
32.000 |
88.58 |
16.22 |
13.14 |
82.42 |
15.19 |
13.36 |
96 |
42.667 |
86.27 |
15.83 |
17.15 |
80.00 |
14.79 |
17.64 |
64 |
64.000 |
80.60 |
14.89 |
32.92 |
74.48 |
13.87 |
33.31 |
48 |
85.333 |
75.29 |
14.01 |
60.68 |
69.10 |
12.98 |
61.90 |
32 |
128.000 |
67.06 |
12.64 |
156.51 |
61.17 |
11.64 |
156.32 |