INA181 datasheet(21/46 Pages) TI1

21 / 46 page

CBYPASS

0.1 µF

2.7 V to 5.5 V

Shutdown

RPULL-UP

10 k

INA181

RSENSE

GND

Load

IN±

IN+

OUT

REF

Bus Voltage

±0.2 V to +26 V

Output

INA181, INA2181, INA4181

www.ti.com

SBOS793C – APRIL 2017 – REVISED DECEMBER 2017

Product Folder Links: INA181 INA2181 INA4181

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Device Functional Modes (continued)

8.4.5 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, there is also a concern for how much current is drained from

the shunt circuit in shutdown conditions. Evaluating this current drain involves considering the simplified

schematic of the INAx181 in shutdown mode, as shown in Figure 46.

Figure 46. Basic Circuit to Shut Down the INA181 With a Grounded Reference

There is typically more than 500 k

Ω 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 k

Ω impedance from the shunt to ground is straightforward.

However, if the reference is powered while the INAx181 is in shutdown mode, instead of assuming 500 k

Ω to

ground, assume 500 k

Ω to the reference voltage.

Regarding the 500-k

Ω 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-k

Ω resistor.

As a final note, 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-k

Ω resistors.

INA181 Datasheet(PDF) 21 Page - Texas Instruments

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