Although the INAx180 do not have a shutdown pin, the low power consumption of the device allows the output of a logic gate or transistor switch to power the INAx180. This gate or switch turns on and off the INAx180 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 INAx180 in shutdown mode, as shown in Figure 44.
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 INAx180 to the OUT pin and to the GND pin. The amount of current flowing through these pins depends on the voltage at the connection.
Regarding the 500-kΩ path to the output pin, the output stage of a disabled INAx180 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 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-kΩ resistors.