Table 8-2. INA229 Noise Performance (continued)

ADC CONVERSION

TIME PERIOD [µs]

OUTPUT SAMPLE

AVERAGING [SAMPLES]

OUTPUT SAMPLE PERIOD

[ms]

NOISE-FREE ENOB

(±163.84-mV)

(ADCRANGE = 0)

NOISE-FREE ENOB

(±40.96-mV)

(ADCRANGE = 1)

50

128

6.4

15.5

13.4

84

10.752

16.3

14.3

150

19.2

16.9

14.7

280

35.84

17.1

15.2

540

69.12

18.1

15.9

1052

134.656

18.1

16.4

2074

265.472

18.7

16.9

4120

527.36

19.7

17.1

50

256

12.8

15.5

14.4

84

21.504

16.7

14.7

150

38.4

17.4

15.3

280

71.68

17.7

15.7

540

138.24

18.7

16.1

1052

269.312

18.7

16.7

2074

530.944

19.7

17.4

4120

1054.72

19.7

17.7

50

512

25.6

16.7

14.3

84

43

17.4

15.4

150

76.8

17.7

15.5

280

143.36

18.7

16.3

540

276.48

18.7

16.5

1052

538.624

19.7

17.4

2074

1061.888

19.7

17.7

4120

2109.44

19.7

18.7

50

1024

51.2

17.1

15.0

84

86.016

17.7

15.9

150

153.6

18.1

16.0

280

286.72

18.7

16.9

540

552.96

19.7

17.1

1052

1077.248

19.7

17.7

2074

2123.776

19.7

18.1

4120

4218.88

20

18.7

8.1.4 Input Filtering Considerations

As previously discussed, INA229 offers several options for noise filtering by allowing the user to select the

conversion times and number of averages independently in the ADC_CONFIG register. The conversion times

can be set independently for the shunt voltage and bus voltage measurements to allow added flexibility in

monitoring of the power-supply bus.

The internal ADC has good inherent noise rejection; however, the transients that occur at or very close to the

sampling rate harmonics can cause problems. Because these signals are at 1 MHz and higher, they can be

managed by incorporating filtering at the input of the device. Filtering high frequency signals enables the use of

low-value series resistors on the filter with negligible effects on measurement accuracy. For best results, filter

using the lowest possible series resistance (typically 100 Ω or less) and a ceramic capacitor. Recommended

values for this capacitor are between 0.1 µF and 1 µF. Figure 8-1 shows the device with a filter added at the

input.

INA229

SLYS023 – DECEMBER 2020

www.ti.com

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