Thermal Hysteresis - Cycle 1 (ppm)

0

10

20

30

40

50

0

10

20

30

40

50

60

70

80

90

Figure 8-6. Thermal Hysteresis Distribution

–40ºC to 85ºC, Cycle 1

Thermal Hysteresis - Cycle 2 (ppm)

0

10

20

30

40

50

0

10

20

30

40

50

60

70

Figure 8-7. Thermal Hysteresis Distribution

–40ºC to 85ºC, Cycle 2

Thermal Hysteresis - Cycle 1 (ppm)

0

6

12

18

24

30

20

30

40

50

60

70

80

90 100 110 120 130

Figure 8-8. Thermal Hysteresis Distribution

–40ºC to 105ºC, Cycle 1

Thermal Hysteresis - Cycle 2 (ppm)

0

10

20

30

40

50

0

10

20

30

40

50

60

70

80

Figure 8-9. Thermal Hysteresis Distribution

–40ºC to 105ºC, Cycle 2

8.5 Noise Performance

The reference pin output noise is categorized as low frequency and broadband noise. The following sections

describe these categories in detail.

8.5.1 Low-Frequency (1/f) Noise

Flicker noise, also known as 1/f noise, is a low-frequency noise that affects the device output voltage which can

affect precision measurements in ADCs. This noise increases proportionally with output voltage and operating

temperature. Noise is measured by filtering the output from 0.1 Hz to 10 Hz. The 1/f noise is an extremely low

value, therefore the frequency of interest must be amplified and band-pass filtered. This is done by using a

high-pass filter to block the DC voltage. The resulting noise is then amplified by a gain of 1000. The bandpass

filter is created by a series of high-pass and low-pass filter that adds additional gain to make it more visible

on a oscilloscope as shown in Figure 8-10. Figure 8-11 shows the effect of flicker noise over 10 second for

REF35250. Flicker noise must be tested in a Faraday cage enclosure to block environmental noise.

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REF35

SNAS809A – DECEMBER 2021 – REVISED AUGUST 2022

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