This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

INA186: Rprotect value

Part Number: INA186

Hi team,

One of my customer will use INA186 and he is asking a question about value of Rprotect.

At customer's application, there would be negative voltage at input and he would like to limit current within 5mA.

He considers to add 2kΩ as Rprotect in figure.33.

  • Is it okay to use 2kΩ as long as they can accept error by Rprotect?
  • Is there maximum limit for Rprotect except for because of error?
  • Is there any other concern by adding current limit resistor?

Best regards,

Shota Mago

  • Hi Shota,

    I would use a diode clamp and two resistors for each input: One resistor in front of the diode clamp to limit the current through the diode and one resistor behind the diode clamp to limit the remaining current into INA186. By this you can keep the sum of resistances below 1k Relaxed

    Kai

  • Hey Shota,

    It is ok with the 2kΩ input resistors. The only concern they would need to address is that the high input resistance can start to degrade internal device operation if there is no input differential capacitor across the input pins. This helps keep the input sense voltage stable similar to proving an input cap for an ADC. I would recommend something greater than or equal to 1nF.

    I also would recommend increasing the resistor slightly so the ESD turn-on current is 3mA at the peak negative voltage for purposes of margin.

    Best,

    Peter

  • Hi Kai and Peter,

    Thanks for your quick response and helpful answer!

    Best regards,

    Shota Mago