INA848 datasheet(16/33 Pages) TI

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8.3.3 Input Protection

The inputs of the INA848 device are individually protected for voltages up to ±20 V which is stated in Section 7.1.

If these rating cannot be met, additional protection circuitry must be considered at the input pins to minimize the

current flowing in case of fault.

During an input overvoltage condition, current flows through the input protection diodes into the power supplies;

see Figure 8-3 . If the power supplies are unable to sink current, then Zener diode clamps (ZD1 and ZD2) must

be placed on the power supplies to provide a current pathway to ground.

V+IN

+VS

V–IN

RIN1

RIN2

GND

ZD1

ZD2

Super- NPN

> +VS

< VS

Figure 8-3. Input Current Path During an Overvoltage Condition

For an overvoltage condition, use an external resistor (RIN1, RIN2) to limit the current. The following equation

gives the calculation for the protection resistors:

IN1=

+IN)F(+

IMAX

(1)

where:

• V+IN is the maximum input voltage

• +VS is the positive supply rail

• IMAX is the maximum current allowed = 10 mA

Calclate RIN2 using the same method, substituting with V–IN, –VS, and –IMAX.

Any additional resistance to the input pins adds more noise to the system. For more details, see Section 9.2.2.2.

8.4 Device Functional Modes

The INA848 has a single functional mode and is operational when the power supply voltage is greater than 4.5 V

(±2.25 V). The maximum power-supply voltage for the INA848 is 36 V (±18 V).

INA848

SBOS946 – SEPTEMBER 2020

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