R

S

Load

V

IN+

-

16Vto+80V

I

S

V

IN+

V

IN

-

+2.7Vto+18V

V+

OUT

INA193-INA198

R

1

R

L

R

2

12

INA193, INA194, INA195

INA196, INA197, INA198

SBOS307G – MAY 2004 – REVISED JANUARY 2015

www.ti.com

Product Folder Links: INA193 INA194 INA195 INA196 INA197 INA198

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Copyright © 2004–2015, Texas Instruments Incorporated

8.3 Feature Description

8.3.1 Basic Connection

Figure 20 shows the basic connection of the INA193-INA198. To minimize any resistance in series with the shunt

resistance, connect the input pins, VIN+ and VIN−, as closely as possible to the shunt resistor.

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. Connect bypass capacitors

close to the device pins.

Figure 20. INA193-INA198 Basic Connection

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 500 mV.

8.3.3 Inside the INA193-INA198

The INA193-INA198 devices use a new, unique internal circuit topology that provides common-mode range

extending from

−16 to 80 V while operating from a single power supply. The common-mode rejection in a classic

instrumentation amplifier approach is limited by the requirement for accurate resistor matching. By converting the

induced input voltage to a current, the INA193-INA198 devices provide common-mode rejection that is no longer

a function of closely matched resistor values, providing the enhanced performance necessary for such a wide

common-mode range. A simplified diagram (shown in Figure 21) shows the basic circuit function. When the

common-mode voltage is positive, amplifier A2 is active.