Thermal Hysteresis - Cycle 1 (ppm)

0

5%

10%

15%

20%

25%

30%

35%

Figure 8-4. Thermal Hysteresis Distribution Cycle 1

(-40°C to 125°C)

Thermal Hysteresis - Cycle 2 (ppm)

0

5%

10%

15%

20%

25%

30%

35%

Figure 8-5. Thermal Hysteresis Distribution Cycle 2

(-40°C to 125°C)

8.4 Noise Performance

8.4.1 1/f Noise

1/f noise, also known as flicker 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. It is measured by filtering the output from 0.1-Hz to 10-Hz. Since the 1/f noise is an extremely

low value, the frequency of interest needs to 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 8-6. 1/f noise must be tested in a Faraday cage enclosure to block

environmental noise.

REF70xx

GND

OUTS

OUTF

VIN EN

VIN

VREFP

High-pass Filter

Low Noise

Preamplifier

G = 1000

2

Low-pass Filter

G = 1

2

Low-pass Filter

G = 10

2

High-pass Filter

G = 10

Scope

Copyright © 2017, Texas Instruments Incorporated

Figure 8-6. 1/f Noise Test Setup

Typical 1/f noise (0.1-Hz to 10-Hz) distribution can be seen in Figure 8-7.

www.ti.com

REF70

SNAS781C – OCTOBER 2020 – REVISED SEPTEMBER 2021

Copyright © 2021 Texas Instruments Incorporated

Submit Document Feedback

19

Product Folder Links: REF70