INA210CIRSWR.B datasheet(16/50 Pages) TI2

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6.4.2 Shutting Down the INA21x Series

Although the INA21x series does 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 INA21x. This gate or switch turns on and turns off the

INA21x 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 INA21x in shutdown mode, as shown in Figure 6-3.

INA21x

V+

OUT

GND

IN-

IN+

PRODUCT

R and R

INA210

INA211

INA212

INA213

INA214

5 kW

2 kW

1 kW

20 kW

10 kW

BYPASS

Shutdown

Control

REF

Reference

Voltage

1 MW

Supply

Load

SHUNT

Output

INA215

13.3 kW

1-MΩ paths from shunt inputs to reference and INA21x outputs.

Figure 6-3. Basic Circuit for Shutting Down The INA21x With a Grounded Reference

Note that there is typically slightly more than 1-MΩ impedance (from the combination of 1-MΩ feedback and

5-kΩ input resistors) from each input of the INA21x to the OUT pin and to the REF pin. The amount of current

flowing through these pins depends on the respective ultimate connection. For example, if the REF pin is

grounded, the calculation of the effect of the 1-MΩ impedance from the shunt to ground is straightforward.

However, if the reference or op amp is powered while the INA21x is shut down, the calculation is direct; instead

of assuming 1 MΩ to ground, however, assume 1 MΩ to the reference voltage. If the reference or op amp is

also shut down, some knowledge of the reference or op amp output impedance under shutdown conditions is

required. For instance, if the reference source behaves as an open circuit when not powered, little or no current

flows through the 1-MΩ path.

Regarding the 1-MΩ path to the output pin, the output stage of a disabled INA21x does constitute a good path

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

1-MΩ resistor.

As a final note, when the device is powered up, there is an additional, nearly constant, and well-matched 25

μA that flows in each of the inputs as long as the shunt common-mode voltage is 3 V or higher. Below 2-V

common-mode, the only current effects are the result of the 1-MΩ resistors.

INA210, INA211, INA212, INA213, INA214, INA215

SBOS437K – MAY 2008 – REVISED NOVEMBER 2023

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