8 Detailed Description

8.1 Overview

The INA183 is a 26-V common-mode, zero-drift topology, current-sensing amplifier meant for high-side, current-

sensing applications. The device is a specially-designed, current-sensing amplifier that can accurately measure

voltages developed across a current-sensing resistor. The device is capable of measuring current on input

voltage rails as high as 26 V and as low as 2.7 V.

The zero-drift topology enables high-precision measurements with maximum input offset voltages as low as

170 µV with a maximum temperature contribution of 0.5 µV/°C over the full temperature range of –40 °C to +125

°C.

8.2 Functional Block Diagram

The simplified functional diagram below shows the device power is provided by the voltage on the IN+ pin. This

diagram also shows the nominal values for the internal gain set resistors. The nominal value of these resistors

can vary by 20% or more; however, the matching between these resistors is tightly controlled. The matching of

these internal resistors results in a precise fixed gain that varies very little over temperature.

_

+

IN-

IN+

GND

OUT

R1

R1

R2

R2

DEVICE

GAIN

R1

R2

INA183A1

50

INA183A2

INA183A3

100

200

1 0Ÿ

20 NŸ

1 0Ÿ

10 NŸ

1 0Ÿ

5 NŸ

8.3 Feature Description

8.3.1 Single-Supply Operation from IN+

The INA183 does not have a dedicated power-supply. Instead, an internal connection to the IN+ pin serves

as the power supply for this device. This allows the device to be used in applications where lower voltage or

sub-regulated supply rails are not present. The operational voltage range on this pin is 2.7 V to 26 V and is

designed for power-supply applications. The maximum current drawn from the IN+ pin is 130 μA, when the

current sense voltage is zero.

8.3.2 Low Gain Error and Offset Voltage

The maximum gain error of the INA183 is 0.4% and is specified over the full operational temperature range.

The low gain error allows for accurate measurements as the sense voltage increases, and is designed for

applications that need to detect overcurrent conditions accurately. The offset voltage of the INA183 is specified

to be ±170 μV for all gain options. The low offset voltage allows for increased accuracy when the sense voltage

is small or allows for reduction in the size of the current sense resistor with less impact on the total measurement

accuracy. Smaller value resistors reduce the power loss in the application which allows the use of lower wattage

resistors that are generally lower cost.

8.3.3 Low Drift Architecture

The INA183 features low drift for both the gain error and offset voltage specifications. The low gain error drift of

10 PPM/ºC results from the well matched internal resistor network that sets the device gain. The low offset drift

INA183

SBOSA08 – FEBRUARY 2021

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