A1

A2

Single-PoleFilter

Capacitor

+2.7Vto+18V

5kW

5kW

96kW

RL

PREOUT

BUFIN

GND

OUT

IN-

IN+

V+

Load

-

16Vto+80V

Supply

R

S

INA270

0.01 F

m

0.1 F

m

11

INA270, INA271

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SBOS381E – FEBRUARY 2007 – REVISED JANUARY 2018

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8.3 Feature Description

8.3.1 Basic Connection

Figure 15 shows the basic connection of the INA270 and INA271. Connect the input pins (IN+ and IN–) as

closely as possible to the shunt resistor to minimize any resistance in series with the shunt resistance.

Power-supply bypass capacitors are required for stability. Applications with noisy or high-impedance power

supplies may require additional decoupling capacitors to reject power-supply noise. Place minimum bypass

capacitors of 0.01 μF and 0.1 μF in value close to the supply pins. Although not mandatory, an additional 10-mF

electrolytic capacitor placed in parallel with the other bypass capacitors may be useful in applications with

particularly noisy supplies.

Figure 15. INA270 Basic Connections

8.3.2 Selecting RS

The value chosen for the shunt resistor, RS, depends on the application and is a compromise between small-

signal accuracy and maximum permissible voltage loss in the measurement line. High values of RS provide better

accuracy at lower currents by minimizing the effects of offset, while low values of RS minimize voltage loss in the

supply line. For most applications, best performance is attained with an RS value that provides a full-scale shunt

voltage range of 50 mV to 100 mV. Maximum input voltage for accurate measurements is (VS – 0.2) / Gain.

8.3.3 Transient Protection

The –16-V to +80-V common-mode range of the INA270 and INA271 is ideal for withstanding automotive fault

conditions ranging from 12-V battery reversal up to +80-V transients because no additional protective

components are needed up to those levels. In the event that the INA270 and INA271 are exposed to transients

on the inputs in excess of their ratings, external transient absorption with semiconductor transient absorbers

(zeners or Transzorbs) are necessary.