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Original question:

INA186: Over voltage on start-up when changing from INA214 to INA186

INA186: we found output of INA186 could not following well the current.

yuguo duan
Prodigy 10 points
Part Number: INA186

Tool/software:

Hello:

we are using INA186A2 in the following schematic, but we found, when the current rising speed is high, and output voltage of INA186 could not follow well the current change? could you please explain the reason?

  • 0
    TI__Expert 7080 points

    Hi Yuguo duan,

    I hope I've understood your question correctly, if you're referring to a time delay in the INA186 response, please note that the INA186 has a step-response delay of ~ 20us, hence a delay is expected when the input rises sharply.

    Aside from that, when a 112A current is passed across a 500u shunt, the votlage developed is 56mV, which gained by 50V/V is 2.8V. The INA186 output from your scope shot appears to meet this.

    Best,
    Mallika Senthil

  • 0
    Prodigy 10 points

    Hello Mallika Senthil:

      thank you very much. From below waveform, we can see clearly, it is not delay issue. any reason that may cause Vout cannot follow the current?

  • 0 in reply to yuguo duan
    TI__Expert 7080 points

    Hi Yuguo duan,

     From the following screenshot, do you know what could be causing the Vout to dip below GND? 

    As a sanity check, I'd recommend depopulating the surrounding devices / resistor-cap networks to narrow-down the issue origin. Please find my suggestions in the screenshot below: (i) Remove the 100pF cap, (ii) Remove the circuit connected to Vout, and probe Vout at the pin.

    Also, what is channel 2 in your scope shot and what kind of load is connected to the shunt. If possible, please send scopeshots of your differential input (IN+ and IN-).

    Best,
    Mallika Senthil