REF7012QFKHT datasheet(22/43 Pages) TI

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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 8-9. 1/f noise must be tested in a Faraday cage enclosure to block

environmental noise.

REF70xx

GND

OUTS

OUTF

VIN EN

VIN

CIN

VREFP

High-pass Filter

FC = 0.07 Hz

Low Noise

Preamplifier

G = 1000

nd Order

Low-pass Filter

FC = 10 Hz

G = 1

nd Order

Low-pass Filter

FC = 10 Hz

G = 10

nd Order

High-pass Filter

FC = 0.1 Hz

G = 10

Scope

Figure 8-9. 1/f Noise Test Setup

Typical 1/f noise (0.1-Hz to 10-Hz) distribution can be seen in Figure 8-10. The noise is measured at two

different supply voltages. The REF70 noise performance is not impacted by supply voltage.

Noise (ppmp-p)

0.1

0.2

0.3

0.4

Vin =5.5V

Vin=12V

Figure 8-10. 0.1-Hz to 10-Hz Voltage Noise Distribution

The 1/f noise is in such a low frequency range that it is not practical to filter out which makes it a key parameter

for ultra-low noise measurements. Noise sensitive designs must use the lowest 1/f noise for the highest precision

measurements. Figure 8-11 shows the effect of 1/f noise over 10s.

REF70

SNAS781G – OCTOBER 2020 – REVISED SEPTEMBER 2023

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