8.3.2 Input Protection

The inputs of the INA851 device are individually protected for voltages up to ±40 V beyond the power supply

impedance under normal signal conditions. If the input is overloaded, the protection circuitry limits the input

current to a value of approximately 22 mA, as Figure 8-3 shows.

-40

-30

-20

-10

0

10

20

30

40

-25

-20

-15

-10

-5

0

5

10

15

20

25

VS =

15 V

VS = 0 V

Figure 8-3. Input Current During an Overvoltage Condition

As shown in Figure 8-4, during an input overvoltage condition, current flows through the input protection diodes

into the power supplies. If the power supplies are unable to sink current, then place Zener diode clamps (ZD1

and ZD2 in Figure 8-4) on the power supplies to provide a current pathway to ground.

VS+

VS–

Overvoltage

Protection

INx

Input Transistor

+

–

Input Voltage

Source

ZD1

ZD2

Figure 8-4. Input Current Path During an Overvoltage Condition

RG terminals, the inputs will still be well protected against overvoltage conditions, but precautions must be taken

to ensure the input differential voltage limitations of the INA851 are not exceeded. For example, a condition of

of external resistors in series with each of the inputs. More detailed guidance is provided in Differential Input

Voltage Limitations.

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INA851

SBOS999 – MARCH 2022

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