Output

INA21x

Load

Supply

ADC

V+

OUT

GND

IN-

IN+

C

BYPASS

0.01mF

to

0.1mF

+2.7Vto+26V

REF

R

1

R

3

R

2

R

4

INA210, INA211, INA212, INA213, INA214, INA215

www.ti.com

SBOS437G – MAY 2008 – REVISED JULY 2014

8.4.3 REF Input Impedance Effects

As with any difference amplifier, the INA210-INA215 series common-mode rejection ratio is affected by any

impedance present at the REF input. This concern is not a problem when the REF pin is connected directly to

most references or power supplies. When using resistive dividers from the power supply or a reference voltage,

the REF pin should be buffered by an op amp.

In systems where the INA210-INA215 output can be sensed differentially, such as by a differential input analog-

to-digital converter (ADC) or by using two separate ADC inputs, the effects of external impedance on the REF

input can be cancelled. Figure 26 depicts a method of taking the output from the INA210-INA215 by using the

REF pin as a reference.

Figure 26. Sensing the INA210-INA215 to Cancel the Effects of Impedance on the REF Input

8.4.4 Using The INA210-INA215 with Common-Mode Transients Above 26 V

With a small amount of additional circuitry, the INA210-INA215 series can be used in circuits subject to transients

higher than 26 V, such as automotive applications. Use only zener diode or zener-type transient absorbers

(sometimes referred to as Transzorbs)—any other type of transient absorber has an unacceptable time delay.

Start by adding a pair of resistors as a working impedance for the zener; see Figure 27. Keeping these resistors

as small as possible is preferable, most often around 10

Ω. Larger values can be used with an effect on gain that

is discussed in the Input Filtering section. Because this circuit is limiting only short-term transients, many

applications are satisfied with a 10-

Ω resistor along with conventional zener diodes of the lowest power rating

that can be found. This combination uses the least amount of board space. These diodes can be found in

packages as small as SOT-523 or SOD-523.

Copyright © 2008–2014, Texas Instruments Incorporated

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