ADS1292 datasheet(7/69 Pages) TI

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SNR = ENOB

6.02

Noise-Free Bits = 2 log

2 V

REF

Gain

Peak-to-Peak Noise

ENOB = 2 log

REF

Gain

RMS Noise

ADS1291

ADS1292

ADS1292R

www.ti.com

SBAS502A – DECEMBER 2011 – REVISED MARCH 2012

PARAMETER MEASUREMENT INFORMATION

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. SNR, noise-free bits, ENOB, and dynamic

range are calculated with Equation 1, Equation 2, and Equation 3.

(1)

(2)

(3)

Table 1. Input-Referred Noise (

μVRMS/μVPP) 3-V Analog Supply and 2.42-V Reference

(1)

PGA GAIN = 1

PGA GAIN = 2

DR BITS

OUTPUT

DATA

–3-dB

NOISE-

CONFIG1

RATE

BANDWIDTH

FREE

(SPS)

(Hz)

μVRMS

μVPP

SNR

BITS

ENOB

μVRMS

μVPP

SNR

BITS

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

104.5

15.57

17.36

5.3

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

—

(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)

PGA GAIN = 3

PGA GAIN = 4

DR BITS

OUTPUT

DATA

–3-dB

NOISE-

CONFIG1

RATE

BANDWIDTH

FREE

(SPS)

(Hz)

μVRMS

μVPP

SNR

BITS

ENOB

μVRMS

μVPP

SNR

BITS

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

103.7

15.65

17.23

2.9

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

—

(1)

At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.

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