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INA186: application problem

Fan Liu
Prodigy 10 points
Part Number: INA186

I have a question about INA186 current sense amplifier. I used this part as a high side differential amplifier to measure a MOSFET switch Rdson.

When the MOSFET switch is OFF,  INA186 INPUT+  is connected to the drain and  INPUT- is to the source. In this case, INPUT- is connected to a resistor to ground.

According to the block diagram of this part, there should be very lo leak current pass through INPUT+ and INPUT- nodes. However, I saw a mA range current flown between INPUT+ and INPUT- path.

Does anyone meet this kind situation? 

  • 0
    TI__Mastermind 31685 points

    Hello Valued Engineer Fan,

    Unfortunately this is most likely an expected behavior. In between the input pins is a diode and ~3.3kΩ resistor to protect input circuitry. Thus, if your differential input voltage (VIN+ - VIN-) exceed a diode forward voltage (~400mV), there will be a dramatic increase in input bias current. I am sorry for any inconvenience. Please let me know if you have other questions and or please post again to the forum.

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    Prodigy 10 points

    Hi Peter,

    I got it.
    Thank you very much.

    Fan