IN+

IN±

OUT

-

+

Buffer

Current

Feedback

5 V

GND

RL

R1

R1

Bias

48-V

Supply

Load

13

INA281

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7.4 Device Functional Modes

7.4.1 Unidirectional Operation

The INA281 measures the differential voltage developed by current flowing through a resistor that is commonly

referred to as a current-sensing resistor or a current-shunt resistor. The INA281 operates in unidirectional mode

only, meaning it only senses current sourced from a power supply to a system load as shown in Figure 28.

Figure 28. Unidirectional Application

The linear range of the output stage is limited to how close the output voltage can approach ground under zero-

input conditions. The zero current output voltage of the INA281 is very small, with a maximum of GND + 20 mV.

Make sure to apply a differential input voltage of (20 mV / Gain) or greater to keep the INA281 output in the

linear region of operation.

7.4.2 High Signal Throughput

With a bandwidth of 1.3 MHz at a gain of 20 V/V and a slew rate of 2.5 V/µs, the INA281 is specifically designed

for detecting and protecting applications from fast inrush currents. As shown in Table 2, the INA281 responds in

less than 2 µs for a system measuring a 75-A threshold on a 2-mΩ shunt.

Table 2. Response Time

PARAMETER

EQUATION

INA281

G

Gain

20 V/V

Maximum current

100 A

Threshold current

75 A

Current sense resistor value

2 mΩ

Output voltage at maximum current

4 V

Output voltage at threshold current

3 V

SR

Slew rate

2.5 V/µs

Output response time

< 2 µs