INA4181A1IPWR.B datasheet(22/62 Pages) TI2

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7.4.5 Shutdown Mode

Although the INAx181 do not have a shutdown pin, the low power consumption of these devices allows the

output of a logic gate or transistor switch to power the INAx181. This gate or switch turns on and off the INAx181

power-supply quiescent current.

However, in current shunt monitoring applications, the amount of current drained from the shunt circuit

in shutdown conditions is also a concern. Evaluating this current drain involves considering the simplified

schematic of the INAx181 in shutdown mode, as shown in Figure 7-8.

CBYPASS

0.1 µF

2.7 V to 5.5 V

Shutdown

RPULL-UP

10 k

RSENSE

GND

Load

IN±

IN+

OUT

REF

Bus Voltage

±0.2 V to +26 V

Output

Single-Channel

TI Device

Figure 7-8. Basic Circuit to Shut Down the INA181 With a Grounded Reference

There is typically more than 500 kΩ of impedance (from the combination of 500-kΩ feedback and

input gain set resistors) from each input of the INAx181 to the OUT pin and to the REF pin. The amount of

current flowing through these pins depends on the voltage at the connection. For example, if the REF pin is

grounded, the calculation of the effect of the 500 kΩ impedance from the shunt to ground is straightforward.

However, if the reference is powered while the INAx181 is in shutdown mode, the input current will be

determined by the 500-kΩ impedance and the voltage difference between the positive input and the voltage

applied to the reference voltage.

Regarding the 500-kΩ path to the output pin, the output stage of a disabled INAx181 does constitute a good path

to ground. Consequently, this current is directly proportional to a shunt common-mode voltage present across a

500-kΩ resistor.

As long as the shunt common-mode voltage is greater than VS when the device is powered up, there is

an additional and well-matched 55-µA typical current that flows in each of the inputs. If less than VS, the

common-mode input currents are negligible, and the only current effects are the result of the 500-kΩ resistors.

INA181, INA2181, INA4181

SBOS793H – APRIL 2017 – REVISED NOVEMBER 2023

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