Bus Supply

±0.2 V to +26 V

High-Side Sensing

Low-Side Sensing

LOAD

is bus-voltage dependent.

is always near ground and is

isolated from bus-voltage spikes.

Direction of Positive

Current Flow

IN+

Direction of Positive

Current Flow

IN±

IN+

IN±

OUT

LOAD

SENSE

REF

V

I

R

GAIN

V

u

u

13

INA181

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SBOS793 – APRIL 2017

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8.3 Feature Description

8.3.1 High Bandwidth and Slew Rate

The INA181 supports small-signal bandwidths as high as 350 kHz, and large-signal slew rates of 2 V/µs. The

ability to detect rapid changes in the sensed current, as well as the ability to quickly slew the output, make the

INA181 a good choice for applications that require a quick response to input current changes. One application

that requires high bandwidth and slew rate is low-side motor control, where the ability to follow rapid changing

current in the motor allows for more accurate control over a wider operating range. Another application that

requires higher bandwidth and slew rates is system fault detection, where the INA181 is used with an external

comparator and a reference to quickly detect when the sensed current is out of range.

8.3.2 Bidirectional Current Monitoring

The INA181 senses current flow through a sense resistor in both directions. The bidirectional current-sensing

capability is achieved by applying a voltage at the REF pin to offset the output voltage. A positive differential

voltage sensed at the inputs results in an output voltage that is greater than the applied reference voltage;

likewise, a negative differential voltage at the inputs results in output voltage that is less than the applied

reference voltage. The output voltage of the current-sense amplifier is shown in Equation 1.

where

•

•

•

GAIN is the gain option of the selected device.

•

(1)

8.3.3 Wide Input Common-Mode Voltage Range

The INA181 supports input common-mode voltages from –0.2 V to +26 V. Because of the internal topology, the

INA181 to be used in high-side, as well as low-side, current-sensing applications, as shown in Figure 34.

Figure 34. High-Side and Low-Side Sensing Connections