ASD1194 datasheet(7/76 Pages) TI

7 / 76 page

ADS1194, ADS1196

ADS1198

www.ti.com

SBAS471C

– APRIL 2010 – REVISED NOVEMBER 2011

NOISE MEASUREMENTS

The ADS1194/6/8 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 PGA value

reduces the input-referred noise, which is particularly useful when measuring low-level biopotential signals.

Table 1 summarizes the noise performance of the ADS1194/6/8, with a 3V analog power supply. Table 2

summarizes the noise performance of the ADS1194/6/8 with a 5V analog power supply. 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. A minimum of 1000

consecutive readings are used to calculate the peak-to-peak noise for each reading. For the two highest data

rates, the noise is limited by quantization noise of the ADC and does not have a gaussian distribution. The ratio

between rms noise and peak-to-peak noise for these two data rates are approximately 10. For the lower data

rates, the ratio is approximately 6.6.

Table 1 and Table 2 show measurements taken with an internal reference. In many of the settlings, espeically at

the lower data rates, the inherent device noise is less than 1LSB. For these cases, the noise is rounded up to

1LSB. The data are also representative of the ADS1194/6/8 noise performance when using a low-noise external

reference such as the REF5025.

Table 1. Input-Referred Noise (

μVPP)

3V Analog Supply and 2.4V Reference(1)(2)

DR BITS OF

OUTPUT

–3dB

CONFIG1

DATA RATE

BANDWIDTH

PGA

(SPS)

(Hz)

GAIN = 1

GAIN = 2

GAIN = 3

GAIN = 4

GAIN = 6

GAIN = 8

GAIN = 12

000

8000

2096

2930

1470

937

681

436

319

205

001

4000

1048

563

265

173

124

010

2000

524

104

9.5

011

1000

262

73.3

36.6

24.4

18.3

12.2

9.2

6.1

100

500

131

73.3

36.6

24.4

18.3

12.2

9.2

6.1

101

250

73.3

36.6

24.4

18.3

12.2

9.2

6.1

110

125

32.5

73.3

36.6

24.4

18.3

12.2

9.2

6.1

(1)

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

(2)

For data rates less than 2kSPS, the noise is rounded up to 1LSB. Input-referred LSB in volts = (2

× VREF/(Gain × 2

16)).

Table 2. Input-Referred Noise (

μVPP)

5V Analog Supply and 4V Reference(1)(2)

DR BITS OF

OUTPUT

–3dB

CONFIG1

DATA RATE

BANDWIDTH

PGA

(SPS)

(Hz)

GAIN = 1

GAIN = 2

GAIN = 3

GAIN = 4

GAIN = 6

GAIN = 8

GAIN = 12

000

8000

2096

4923

2450

1598

1196

765

560

362

001

4000

1048

959

481

307

222

142

100

010

2000

524

166

12.3

011

1000

262

122.1

61.1

40.7

30.5

20.4

15.3

10.2

100

500

131

122.1

61.1

40.7

30.5

20.4

15.3

10.2

101

250

122.1

61.1

40.7

30.5

20.4

15.3

10.2

110

125

32.5

122.1

61.1

40.7

30.5

20.4

15.3

10.2

(1)

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

(2)

For data rates less than 2kSPS, the noise is rounded up to 1LSB. Input-referred LSB in volts = (2

× VREF/(Gain × 2

16)).

Table 3. Typical WCT Performance

ANY ONE

ANY TWO

ALL THREE

PARAMETER

(A, B, or C)

(A+B, A+C, or B+C)

(A+B+C)

UNIT

Noise

563

404

330

nVRMS

Power

μA

–3dB BW

kHz

Slew rate

BW limited

—

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