6.4.2 Shutting Down the INA21x-Q1 Series

While the INA21x-Q1 family of devices 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 device. This gate or switch turns on and turns

off the INA21x-Q1 power-supply quiescent current.

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

shutdown conditions must be considered. Evaluating this current drain involves considering the simplified

schematic of the INA21x-Q1 family of devices in shutdown mode shown in Figure 6-3.

INA21x-Q1

V+

OUT

GND

IN-

IN+

PRODUCT

R and R

3

4

INA210-Q1

INA211-Q1

INA212-Q1

INA213-Q1

INA214-Q1

5 kW

2 kW

1 kW

20 kW

10 kW

C

BYPASS

Shutdown

Control

REF

Reference

Voltage

1 MW

R

3

1 MW

R

4

Supply

Load

R

SHUNT

Output

INA215-Q1

13.3 kW

Copyright © 2017, Texas Instruments Incorporated

1-MΩ paths from shunt inputs to reference and INA21x-Q1 outputs.

Figure 6-3. Basic Circuit for Shutting Down INA21x-Q1 With a Grounded Reference

Slightly more than a 1-MΩ impedance (from the combination of 1-MΩ feedback and 5-kΩ input resistors) exists

from each input of the INA21x-Q1 family of devices 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 operational amplifier (op amp) is powered when the INA21x-Q1 family of devices

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-Q1 device 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.

Note

When the device is powered up, an additional, nearly constant and well-matched 25-µA current

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.

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INA210-Q1, INA211-Q1, INA212-Q1, INA213-Q1, INA214-Q1, INA215-Q1

SBOS475K – MARCH 2009 – REVISED NOVEMBER 2023

Copyright © 2023 Texas Instruments Incorporated

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