INA21x

V+

OUT

GND

IN-

IN+

PRODUCT

R and R

3

4

INA210

INA211

INA212

INA213

INA214

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

13.3 kW

INA210, INA211, INA212, INA213, INA214, INA215

SBOS437G – MAY 2008 – REVISED JULY 2014

www.ti.com

8.4.2 Shutting Down the INA210-INA215 Series

While the INA210-INA215 series does not have a shutdown pin, its low power consumption allows powering from

the output of a logic gate or transistor switch that can turn on and turn off the INA210-INA215 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 INA210-INA215 in shutdown mode shown in Figure 25.

NOTE: 1-M

Ω paths from shunt inputs to reference and INA21x outputs.

Figure 25. Basic Circuit for Shutting Down the INA210-INA215 with a Grounded Reference

Note that there is typically slightly more than 1-M

Ω impedance (from the combination of 1-MΩ feedback and

5-k

Ω input resistors) from each input of the INA210-INA215 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-M

Ω impedance from the shunt to ground is straightforward.

However, if the reference or op amp is powered while the INA210-INA215 is shut down, the calculation is direct;

instead of assuming 1 M

Ω 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 is not powered, little

or no current flows through the 1-M

Ω path.

Regarding the 1-M

Ω path to the output pin, the output stage of a disabled INA210-INA215 does constitute a

good path to ground; consequently, this current is directly proportional to a shunt common-mode voltage

impressed across a 1-M

Ω 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-M

Ω resistors.

16

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