10

30

50

70

90

110

10M

100M

1G

10G

Frequency (Hz)

C001

10

30

50

70

90

110

10M

100M

1G

10G

Frequency (Hz)

C001

EMIRR (dB)

2

RF _ PEAK

20

OS

P

V

V

10

100 mV

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18

INA828

SBOS792A – AUGUST 2017 – REVISED JANUARY 2018

www.ti.com

Product Folder Links: INA828

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Copyright © 2017–2018, Texas Instruments Incorporated

7.3.1.1 Gain Drift

The stability and temperature drift of the external gain setting resistor, RG, also affects gain. The contribution of

RG to gain accuracy and drift can be determined from Equation 1.

The best gain drift of 5 ppm/

℃ (maximum) can be achieved when the INA828 uses G = 1 without RG connected.

In this case, gain drift is limited only by the slight mismatch of the temperature coefficient of the integrated 40-kΩ

resistors in the differential amplifier (A3). At gains greater than 1, gain drift increases as a result of the individual

drift of the 25-kΩ resistors in the feedback of A1 and A2, relative to the drift of the external gain resistor RG. The

low temperature coefficient of the internal feedback resistors significantly improves the overall temperature

stability of applications using gains greater than 1 V/V over alternate solutions.

Low resistor values required for high gain can make wiring resistance important. Sockets add to the wiring

resistance and contribute additional gain error (such as a possible unstable gain error) at gains of approximately

100 or greater. To assure stability, avoid parasitic capacitance of more than a few picofarads at RG connections.

Careful matching of any parasitics on both RG pins maintains optimal CMRR over frequency; see Typical

Characteristics, Figure 17.

7.3.2 EMI Rejection

Texas Instruments developed a method to accurately measure the immunity of an amplifier over a broad

frequency spectrum, extending from 10 MHz to 6 GHz. This method uses an EMI rejection ratio (EMIRR) to

quantify the ability of the INA828 to reject EMI. The offset resulting from an input EMI signal can be calculated

using Equation 2:

where

•

VRF_PEAK is the peak amplitude of the input EMI signal.

(2)

Figure 53 and Figure 54 show the INA828 EMIRR graph for both differential and common-mode EMI rejection

across this frequency range. Table 2 shows the EMIRR values for the INA828 at frequencies commonly

encountered in real-world applications. Applications listed in Table 2 can be centered on or operated near the

particular frequency shown. Depending on the end-system requirements, additional EMI filters may be required

near the signal inputs of the system, as well as incorporating known good practices such as using short traces,

low-pass filters, and damping resistors combined with parallel and shielded signal routing.

Figure 53. Common-Mode EMIRR Testing

Figure 54. Differential Mode EMIRR Testing