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.

For an overvoltage condition, use an external resistor (R_IN1, R_IN2) to limit the current. The following equation gives the calculation for the protection resistors:

Equation 1.

where:

• V_+IN is the maximum input voltage
• +V_S is the positive supply rail
• I_MAX is the maximum current allowed = 10 mA

Calclate R_IN2 using the same method, substituting with V_–IN, –V_S, and –I_MAX.

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